1.
Greek language
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Greek is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records and its writing system has been the Greek alphabet for the major part of its history, other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems. Together with the Latin texts and traditions of the Roman world, during antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and many places beyond. It would eventually become the official parlance of the Byzantine Empire, the language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora. Greek roots are used to coin new words for other languages, Greek. Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, the earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the worlds oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now extinct Anatolian languages, the Greek language is conventionally divided into the following periods, Proto-Greek, the unrecorded but assumed last ancestor of all known varieties of Greek. The unity of Proto-Greek would have ended as Hellenic migrants entered the Greek peninsula sometime in the Neolithic era or the Bronze Age, Mycenaean Greek, the language of the Mycenaean civilisation. It is recorded in the Linear B script on tablets dating from the 15th century BC onwards, Ancient Greek, in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilisation. It was widely known throughout the Roman Empire, after the Roman conquest of Greece, an unofficial bilingualism of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. The origin of Christianity can also be traced through Koine Greek, Medieval Greek, also known as Byzantine Greek, the continuation of Koine Greek in Byzantine Greece, up to the demise of the Byzantine Empire in the 15th century. Much of the written Greek that was used as the language of the Byzantine Empire was an eclectic middle-ground variety based on the tradition of written Koine. Modern Greek, Stemming from Medieval Greek, Modern Greek usages can be traced in the Byzantine period and it is the language used by the modern Greeks, and, apart from Standard Modern Greek, there are several dialects of it. In the modern era, the Greek language entered a state of diglossia, the historical unity and continuing identity between the various stages of the Greek language is often emphasised. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language and it is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English, Greek is spoken by about 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Greek is the language of Greece, where it is spoken by almost the entire population
2.
Carbohydrate
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A carbohydrate is a biological molecule consisting of carbon, hydrogen and oxygen atoms, usually with a hydrogen–oxygen atom ratio of 2,1, in other words, with the empirical formula Cmn. This formula holds true for monosaccharides, some exceptions exist, for example, deoxyribose, a sugar component of DNA, has the empirical formula C5H10O4. Carbohydrates are technically hydrates of carbon, structurally it is accurate to view them as polyhydroxy aldehydes and ketones. The term is most common in biochemistry, where it is a synonym of saccharide, a group that includes sugars, starch, the saccharides are divided into four chemical groups, monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides and disaccharides, the smallest carbohydrates, are referred to as sugars. The word saccharide comes from the Greek word σάκχαρον, meaning sugar, while the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose. For example, grape sugar is the glucose, cane sugar is the disaccharide sucrose. Carbohydrates perform numerous roles in living organisms, polysaccharides serve for the storage of energy and as structural components. The 5-carbon monosaccharide ribose is an important component of coenzymes and the backbone of the genetic molecule known as RNA, the related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the system, fertilization, preventing pathogenesis, blood clotting. In food science and in informal contexts, the term carbohydrate often means any food that is particularly rich in the complex carbohydrate starch or simple carbohydrates. Often in lists of information, such as the USDA National Nutrient Database, the term carbohydrate is used for everything other than water, protein, fat, ash. This will include chemical compounds such as acetic or lactic acid, carbohydrates are found in wide variety of foods. The important sources are cereals, potatoes, sugarcane, fruits, table sugar, bread, milk, starch and sugar are the important carbohydrates in our diet. Starch is abundant in potatoes, maize, rice and other cereals, sugar appears in our diet mainly as sucrose which is added to drinks and many prepared foods such as jam, biscuits and cakes. Glucose and fructose are found naturally in fruits and some vegetables. Glycogen is carbohydrate found in the liver and muscles, cellulose in the cell wall of all plant tissue is a carbohydrate. It is important in our diet as fibre which helps to maintain a healthy digestive system, formerly the name carbohydrate was used in chemistry for any compound with the formula Cm n
3.
Hydrolysis
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Hydrolysis usually means the cleavage of chemical bonds by the addition of water. When a carbohydrate is broken into its component sugar molecules by hydrolysis, generally, hydrolysis or saccharification is a step in the degradation of a substance. Hydrolysis can be the reverse of a reaction in which two molecules join together into a larger one and eject a water molecule. Thus hydrolysis adds water to break down, whereas condensation builds up by removing water, usually hydrolysis is a chemical process in which a molecule of water is added to a substance. Sometimes this addition causes both substance and water molecule to split into two parts, in such reactions, one fragment of the target molecule gains a hydrogen ion. A common kind of hydrolysis occurs when a salt of an acid or weak base is dissolved in water. Water spontaneously ionizes into hydroxide anions and hydronium cations, the salt also dissociates into its constituent anions and cations. For example, sodium acetate dissociates in water into sodium and acetate ions, sodium ions react very little with the hydroxide ions whereas the acetate ions combine with hydronium ions to produce acetic acid. In this case the net result is an excess of hydroxide ions. For example, dissolving sulfuric acid in water is accompanied by hydrolysis to give hydronium and bisulfate, for a more technical discussion of what occurs during such a hydrolysis, see Brønsted–Lowry acid–base theory. Acid–base-catalysed hydrolyses are very common, one example is the hydrolysis of amides or esters and their hydrolysis occurs when the nucleophile attacks the carbon of the carbonyl group of the ester or amide. In an aqueous base, hydroxyl ions are better nucleophiles than polar molecules such as water, in acids, the carbonyl group becomes protonated, and this leads to a much easier nucleophilic attack. The products for both hydrolyses are compounds with carboxylic acid groups, perhaps the oldest commercially practiced example of ester hydrolysis is saponification. It is the hydrolysis of a triglyceride with a base such as sodium hydroxide. During the process, glycerol is formed, and the fatty acids react with the base and these salts are called soaps, commonly used in households. In addition, in living systems, most biochemical reactions take place during the catalysis of enzymes, the catalytic action of enzymes allows the hydrolysis of proteins, fats, oils, and carbohydrates. As an example, one may consider proteases and they catalyse the hydrolysis of interior peptide bonds in peptide chains, as opposed to exopeptidases. However, proteases do not catalyse the hydrolysis of all kinds of proteins and their action is stereo-selective, Only proteins with a certain tertiary structure are targeted as some kind of orienting force is needed to place the amide group in the proper position for catalysis
4.
Sugar
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Sugar is the generic name for sweet, soluble carbohydrates, many of which are used in food. There are various types of derived from different sources. Simple sugars are called monosaccharides and include glucose, fructose, the table sugar or granulated sugar most customarily used as food is sucrose, a disaccharide of glucose and fructose. Sugar is used in prepared foods and it is added to some foods, in the body, sucrose is hydrolysed into the simple sugars fructose and glucose. Other disaccharides include maltose from malted grain, and lactose from milk, longer chains of sugars are called oligosaccharides or polysaccharides. Some other chemical substances, such as glycerol may also have a sweet taste, low-calorie food substitutes for sugar, described as artificial sweeteners, include aspartame and sucralose, a chlorinated derivative of sucrose. Sugars are found in the tissues of most plants and are present in sufficient concentrations for efficient commercial extraction in sugarcane, the world production of sugar in 2011 was about 168 million tonnes. The average person consumes about 24 kilograms of sugar each year, equivalent to over 260 food calories per person, since the latter part of the twentieth century, it has been questioned whether a diet high in sugars, especially refined sugars, is good for human health. Sugar has been linked to obesity, and suspected of, or fully implicated as a cause in the occurrence of diabetes, cardiovascular disease, dementia, macular degeneration, the etymology reflects the spread of the commodity. The English word sugar ultimately originates from the Sanskrit शर्करा, via Arabic سكر as granular or candied sugar, the contemporary Italian word is zucchero, whereas the Spanish and Portuguese words, azúcar and açúcar, respectively, have kept a trace of the Arabic definite article. The Old French word is zuchre and the contemporary French, sucre, the earliest Greek word attested is σάκχαρις. The English word jaggery, a brown sugar made from date palm sap or sugarcane juice, has a similar etymological origin – Portuguese jagara from the Sanskrit शर्करा. Sugar has been produced in the Indian subcontinent since ancient times and it was not plentiful or cheap in early times and honey was more often used for sweetening in most parts of the world. Originally, people chewed raw sugarcane to extract its sweetness, sugarcane was a native of tropical South Asia and Southeast Asia. Different species seem to have originated from different locations with Saccharum barberi originating in India and S. edule, one of the earliest historical references to sugarcane is in Chinese manuscripts dating back to 8th century BC that state that the use of sugarcane originated in India. Sugar was found in Europe by the 1st century AD, but only as an imported medicine and it is a kind of honey found in cane, white as gum, and it crunches between the teeth. It comes in lumps the size of a hazelnut, sugar is used only for medical purposes. Sugar remained relatively unimportant until the Indians discovered methods of turning sugarcane juice into granulated crystals that were easier to store, crystallized sugar was discovered by the time of the Imperial Guptas, around the 5th century AD
5.
Transparency and translucency
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In the field of optics, transparency is the physical property of allowing light to pass through the material without being scattered. On a macroscopic scale, the photons can be said to follow Snells Law, in other words, a translucent medium allows the transport of light while a transparent medium not only allows the transport of light but allows for image formation. The opposite property of translucency is opacity, transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color. When light encounters a material, it can interact with it in different ways. These interactions depend on the wavelength of the light and the nature of the material, photons interact with an object by some combination of reflection, absorption and transmission. Some materials, such as glass and clean water, transmit much of the light that falls on them and reflect little of it. Many liquids and aqueous solutions are highly transparent, absence of structural defects and molecular structure of most liquids are mostly responsible for excellent optical transmission. Materials which do not transmit light are called opaque, many such substances have a chemical composition which includes what are referred to as absorption centers. Many substances are selective in their absorption of light frequencies. They absorb certain portions of the spectrum while reflecting others. The frequencies of the spectrum which are not absorbed are either reflected or transmitted for our physical observation and this is what gives rise to color. The attenuation of light of all frequencies and wavelengths is due to the mechanisms of absorption. Transparency can provide almost perfect camouflage for animals able to achieve it and this is easier in dimly-lit or turbid seawater than in good illumination. Many marine animals such as jellyfish are highly transparent, at the atomic or molecular level, physical absorption in the infrared portion of the spectrum depends on the frequencies of atomic or molecular vibrations or chemical bonds, and on selection rules. Nitrogen and oxygen are not greenhouse gases because there is no absorption because there is no molecular dipole moment. With regard to the scattering of light, the most critical factor is the scale of any or all of these structural features relative to the wavelength of the light being scattered. Primary material considerations include, Crystalline structure, whether or not the atoms or molecules exhibit the long-range order evidenced in crystalline solids, glassy structure, scattering centers include fluctuations in density or composition. Microstructure, scattering centers include internal surfaces such as boundaries, crystallographic defects
6.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
7.
Solubility
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Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent. The solubility of a substance depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure. The solubility of a substance is a different property from the rate of solution. Most often, the solvent is a liquid, which can be a substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas, the extent of solubility ranges widely, from infinitely soluble such as ethanol in water, to poorly soluble, such as silver chloride in water. The term insoluble is often applied to poorly or very poorly soluble compounds, a common threshold to describe something as insoluble is less than 0.1 g per 100 mL of solvent. Under certain conditions, the solubility can be exceeded to give a so-called supersaturated solution. Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its form or particle size. A supersaturated solution generally crystallises when seed crystals are introduced and rapid equilibration occurs, phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point. Solubility is not to be confused with the ability to dissolve a substance, for example, zinc dissolves in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid, the smaller a particle is, the faster it dissolves although there are many factors to add to this generalization. Crucially solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic, in all cases it will depend on the physical conditions and the enthalpy and entropy directly relating to the solvents and solutes concerned. By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a range of organic substances. This is a factor in acidity/alkalinity and much environmental and geochemical work. According to the IUPAC definition, solubility is the composition of a saturated solution expressed as a proportion of a designated solute in a designated solvent. Solubility may be stated in units of concentration such as molarity, molality, mole fraction, mole ratio, mass per volume. Solubility occurs under dynamic equilibrium, which means that solubility results from the simultaneous and opposing processes of dissolution, the solubility equilibrium occurs when the two processes proceed at a constant rate. The term solubility is used in some fields where the solute is altered by solvolysis
8.
Crystal
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A crystal or crystalline solid is a solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, the scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification, the word crystal derives from the Ancient Greek word κρύσταλλος, meaning both ice and rock crystal, from κρύος, icy cold, frost. Examples of large crystals include snowflakes, diamonds, and table salt, most inorganic solids are not crystals but polycrystals, i. e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most metals, rocks, ceramics, a third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass, wax, and many plastics, Crystals are often used in pseudoscientific practices such as crystal therapy, and, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements. The scientific definition of a crystal is based on the arrangement of atoms inside it. A crystal is a solid where the form a periodic arrangement. For example, when liquid water starts freezing, the change begins with small ice crystals that grow until they fuse. Most macroscopic inorganic solids are polycrystalline, including almost all metals, ceramics, ice, rocks, solids that are neither crystalline nor polycrystalline, such as glass, are called amorphous solids, also called glassy, vitreous, or noncrystalline. These have no periodic order, even microscopically, there are distinct differences between crystalline solids and amorphous solids, most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does. A crystal structure is characterized by its cell, a small imaginary box containing one or more atoms in a specific spatial arrangement. The unit cells are stacked in three-dimensional space to form the crystal, the symmetry of a crystal is constrained by the requirement that the unit cells stack perfectly with no gaps. There are 219 possible crystal symmetries, called space groups. These are grouped into 7 crystal systems, such as cubic crystal system or hexagonal crystal system, Crystals are commonly recognized by their shape, consisting of flat faces with sharp angles. Euhedral crystals are those with obvious, well-formed flat faces, anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid. The flat faces of a crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal. This occurs because some surface orientations are more stable than others, as a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces
9.
Sweetness
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Sweetness is a basic taste most commonly perceived when eating foods rich in sugars. Sweet tastes are universally regarded as an experience, except perhaps in excess. Fructose is sweeter than glucose and sucrose and this has made possible the production of sugar syrups with the sweetness and certain other properties of sucrose starting from starch. In addition to sugars like sucrose, many chemical compounds are sweet, including aldehydes, ketones. Some are sweet at very low concentrations, allowing their use as sugar substitutes. Such non-sugar sweeteners include saccharin and asapartame, other compounds, such as miraculin, may alter perception of sweetness itself. The chemosensory basis for detecting sweetness, which varies between individuals and species, has only begun to be understood since the late 20th century. One theoretical model of sweetness is the multipoint attachment theory, which involves multiple binding sites between a receptor and a sweet substance. Studies indicate that responsiveness to sugars and sweetness has very ancient evolutionary beginnings, newborn human infants also demonstrate preferences for high sugar concentrations and prefer solutions that are sweeter than lactose, the sugar found in breast milk. Sweetness appears to have the highest taste recognition threshold, being detectable at around 1 part in 200 of sucrose in solution, by comparison, bitterness appears to have the lowest detection threshold, at about 1 part in 2 million for quinine in solution. Even amongst leaf-eating primates, there is a tendency to prefer immature leaves, the sweet tooth thus has an ancient evolutionary heritage, and while food processing has changed consumption patterns, human physiology remains largely unchanged. A great diversity of compounds, such as aldehydes and ketones are sweet. Among common biological substances, all of the carbohydrates are sweet to at least some degree. Sucrose is the example of a sweet substance. Sucrose in solution has a sweetness perception rating of 1, for example, another sugar, fructose, is somewhat sweeter, being rated at 1.7 times the sweetness of sucrose. Some of the acids are mildly sweet, alanine, glycine. Some other amino acids are perceived as sweet and bitter. A number of plant species produce glycosides that are sweet at concentrations lower than sugar
10.
Fructose
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Fructose, or fruit sugar, is a simple ketonic monosaccharide found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion, fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847. The name fructose was coined in 1857 by the English chemist William Miller, pure, dry fructose is a very sweet, white, odorless, crystalline solid and is the most water-soluble of all the sugars. Fructose is found in honey, tree and vine fruits, flowers, berries, commercially, fructose is frequently derived from sugar cane, sugar beets, and corn. Crystalline fructose is the monosaccharide, dried, ground, and of high purity, high-fructose corn syrup is a mixture of glucose and fructose as monosaccharides. Sucrose is a compound with one molecule of glucose covalently linked to one molecule of fructose, all forms of fructose, including fruits and juices, are commonly added to foods and drinks for palatability and taste enhancement, and for browning of some foods, such as baked goods. About 240,000 tonnes of crystalline fructose are produced annually, leads to adverse health outcomes independent of any effects related to its presence as a component of total and free sugars. Crystalline fructose adopts a cyclic six-membered structure owing to the stability of its hemiketal and internal hydrogen-bonding and this form is formally called D-fructopyranose. In solution, fructose exists as a mixture of 70% fructopyranose and about 22% fructofuranose. Fructose may be fermented by yeast or bacteria. Yeast enzymes convert sugar to ethanol and carbon dioxide, the carbon dioxide released during fermentation will remain dissolved in water, where it will reach equilibrium with carbonic acid, unless the fermentation chamber is left open to the air. The dissolved carbon dioxide and carbonic acid produce the carbonation in bottled fermented beverages, fructose undergoes the Maillard reaction, non-enzymatic browning, with amino acids. Because fructose exists to an extent in the open-chain form than does glucose. Fructose readily dehydrates to give hydroxymethylfurfural and this process, in the future, may become part of a low-cost, carbon-neutral system to produce replacements for petrol and diesel from plants. The primary reason that fructose is used commercially in foods and beverages, besides its low cost, is its high relative sweetness and it is the sweetest of all naturally occurring carbohydrates. The relative sweetness of fructose has been reported in the range of 1. 2–1.8 times that of sucrose, however, it is the 6-membered ring form of fructose that is sweeter, the 5-membered ring form tastes about the same as usual table sugar. Warming fructose leads to formation of the 5-membered ring form, therefore, the relative sweetness decreases with increasing temperature. The sweetness of fructose is perceived earlier than that of sucrose or glucose, fructose can also enhance other flavors in the system
11.
Sucrose
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Sucrose is a common saccharide found in many plants and plant parts. Saccharose is a term for sugars in general, especially sucrose. The molecule is a combination of the monosaccharides glucose and fructose with the formula C12H22O11. Sucrose is often extracted and refined from either sugarcane or beet sugar for human consumption, modern industrial sugar refinement processes often involve bleaching and crystallization, producing a white, odorless, crystalline powder with a sweet taste of pure sucrose. This refined form of sucrose is commonly referred to as sugar or just sugar. It plays a role as an additive in food production all over the world. About 175 million metric tons of sucrose were produced worldwide in 2013, the term sucrose was first used in 1857 by English chemist William Miller from the French sucre and the generic chemical suffix for sugars -ose. The abbreviated term Suc is often used for sucrose in scientific literature, in sucrose, the components glucose and fructose are linked via an acetal bond between C1 on the glucosyl subunit and C2 on the fructosyl unit. The bond is called a glycosidic linkage, glucose exists predominantly as two isomeric pyranoses, but only one of these forms links to the fructose. Fructose itself exists as a mixture of furanoses, each of which having α and β isomers and this linkage inhibits further bonding to other saccharide units. Since it contains no anomeric hydroxyl groups, it is classified as a non-reducing sugar. Sucrose crystallizes in the space group P21 with room-temperature lattice parameters a =1.08631 nm, b =0.87044 nm, c =0.77624 nm. The purity of sucrose is measured by polarimetry, through the rotation of plane-polarized light by a solution of sugar, the specific rotation at 20 °C using yellow sodium-D light is +66. 47°. Commercial samples of sugar are assayed using this parameter, Sucrose does not deteriorate at ambient conditions. The formula for sucrose decomposition can be represented as a 2 step reaction, C12H22O11 + heat → 12C + 11H2O 12C + 12O2 → 12CO2 Sucrose does not melt at high temperatures. Instead, it decomposes—at 186 °C —to form caramel, like other carbohydrates, it combusts to carbon dioxide and water. Mixing sucrose with the potassium nitrate produces the fuel known as rocket candy that is used to propel amateur rocket motors. C12H22O11 +6 KNO3 →9 CO +3 N2 +11 H2O +3 K2CO3 This reaction is somewhat simplified though, some of the carbon does get fully oxidized to carbon dioxide, and other reactions, such as the water-gas shift reaction also take place
12.
Lactose
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Lactose is a disaccharide sugar composed of galactose and glucose that is found in milk. Lactose makes up around 2–8% of milk, although the amount varies among species and individuals and it is extracted from sweet or sour whey. The name comes from lac, the Latin word for milk and it has a formula of C12H22O11 and the hydrate formula C12H22O11·H2O, making it an isomer of sucrose. The first crude isolation of lactose, by Italian physician Fabrizio Bartoletti, was published in 1633, in 1700, the Venetian pharmacist Lodovico Testi published a booklet of testimonials to the power of milk sugar to relieve, among other ailments, the symptoms of arthritis. In 1715, Testis procedure for making milk sugar was published by Antonio Vallisneri, lactose was identified as a sugar in 1780 by Carl Wilhelm Scheele. In 1812, Heinrich Vogel recognized that glucose was a product of hydrolyzing lactose, in 1856, Louis Pasteur crystallized the other component of lactose, galactose. By 1894, Emil Fischer had established the configurations of the component sugars, lactose was named by the French chemist Jean Baptiste André Dumas in 1843. Lactose is a derived from the condensation of galactose and glucose. Lactose is hydrolysed to glucose and galactose, isomerised in alkaline solution to lactulose, lactose monohydrate crystals have a characteristic tomahawk shape that can be observed with a light microscope. Several million tons are produced annually as a by-product of the dairy industry, whey is made up of 6. 5% solids of which 4. 8% is lactose that may be purified by crystallisation. Whey or milk plasma is the liquid remaining after milk is curdled and strained, lactose makes up about 2–8% of milk by weight. Industrially, lactose is produced from whey permeate – that is whey filtrated for all major proteins, the protein fraction is used in infant nutrition and sport nutrition while the permeate can be evaporated to 60–65% solids and crystallized while cooling. Lactose can also be precipitated from whey using ethanol, since it is insoluble in ethanol, lactose precipitates, in about 65% yield. Infant mammals nurse on their mothers to drink milk, which is rich in lactose, the intestinal villi secrete the enzyme called lactase to digest it. This enzyme cleaves the molecule into its two subunits, the simple sugars glucose and galactose, which can be absorbed. Since lactose occurs mostly in milk, in most mammals, the production of lactase gradually decreases with maturity due to a lack of continuing consumption. Many people with ancestry in Europe, West Asia, South Asia, the Sahel belt in West Africa, East Africa, in many of these areas, milk from mammals such as cattle, goats, and sheep is used as a large source of food. Hence, it was in these regions that genes for lifelong lactase production first evolved, the genes of adult lactose tolerance have evolved independently in various ethnic groups
13.
Polysaccharide
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They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose, polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their building blocks. They may be amorphous or even insoluble in water, natural saccharides are generally of simple carbohydrates called monosaccharides with general formula n where n is three or more. Examples of monosaccharides are glucose, fructose, and glyceraldehyde, polysaccharides, meanwhile, have a general formula of Cxy where x is usually a large number between 200 and 2500. When the repeating units in the backbone are six-carbon monosaccharides, as is often the case, the general formula simplifies to n. Polysaccharides are an important class of biological polymers and their function in living organisms is usually either structure- or storage-related. Starch is used as a polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar glucose polymer is the more densely branched glycogen, glycogens properties allow it to be metabolized more quickly, which suits the active lives of moving animals. Cellulose and chitin are examples of structural polysaccharides, cellulose is used in the cell walls of plants and other organisms, and is said to be the most abundant organic molecule on Earth. It has many such as a significant role in the paper and textile industries, and is used as a feedstock for the production of rayon, cellulose acetate, celluloid. Chitin has a structure, but has nitrogen-containing side branches. It is found in arthropod exoskeletons and in the walls of some fungi. It also has multiple uses, including surgical threads, polysaccharides also include callose or laminarin, chrysolaminarin, xylan, arabinoxylan, mannan, fucoidan and galactomannan. Nutrition polysaccharides are common sources of energy, many organisms can easily break down starches into glucose, however, most organisms cannot metabolize cellulose or other polysaccharides like chitin and arabinoxylans. These carbohydrate types can be metabolized by bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose, even though these complex carbohydrates are not very digestible, they provide important dietary elements for humans. Called dietary fiber, these carbohydrates enhance digestion among other benefits, the main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract, and to change how other nutrients and chemicals are absorbed
14.
Cellulose
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Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β linked D-glucose units. Cellulose is an important structural component of the cell wall of green plants, many forms of algae. Some species of bacteria secrete it to form biofilms, Cellulose is the most abundant organic polymer on Earth. The cellulose content of cotton fiber is 90%, that of wood is 40–50%, Cellulose is mainly used to produce paperboard and paper. Smaller quantities are converted into a variety of derivative products such as cellophane. Conversion of cellulose from energy crops into biofuels such as ethanol is under investigation as an alternative fuel source. Cellulose for industrial use is mainly obtained from wood pulp and cotton, some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In humans, cellulose acts as a bulking agent for feces and is often referred to as a dietary fiber. Cellulose was discovered in 1838 by the French chemist Anselme Payen, Cellulose was used to produce the first successful thermoplastic polymer, celluloid, by Hyatt Manufacturing Company in 1870. Production of rayon from cellulose began in the 1890s and cellophane was invented in 1912, hermann Staudinger determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized in 1992, by Kobayashi, Cellulose has no taste, is odorless, is hydrophilic with the contact angle of 20–30 degrees, is insoluble in water and most organic solvents, is chiral and is biodegradable. It was shown to melt at 467 °C in 2016 and it can be broken down chemically into its glucose units by treating it with concentrated mineral acids at high temperature. Cellulose is derived from D-glucose units, which condense through β-glycosidic bonds and this linkage motif contrasts with that for α-glycosidic bonds present in starch and glycogen. This confers tensile strength in cell walls, where cellulose microfibrils are meshed into a polysaccharide matrix, compared to starch, cellulose is also much more crystalline. Whereas starch undergoes a crystalline to amorphous transition when heated beyond 60–70 °C in water, cellulose requires a temperature of 320 °C, several different crystalline structures of cellulose are known, corresponding to the location of hydrogen bonds between and within strands. Natural cellulose is cellulose I, with structures Iα and Iβ, Cellulose produced by bacteria and algae is enriched in Iα while cellulose of higher plants consists mainly of Iβ. Cellulose in regenerated cellulose fibers is cellulose II, the conversion of cellulose I to cellulose II is irreversible, suggesting that cellulose I is metastable and cellulose II is stable. With various chemical treatments it is possible to produce the structures cellulose III, many properties of cellulose depend on its chain length or degree of polymerization, the number of glucose units that make up one polymer molecule
15.
Starch
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Starch or amylum is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as an energy store and it is the most common carbohydrate in human diets and is contained in large amounts in staple foods such as potatoes, wheat, maize, rice, and cassava. Pure starch is a white, tasteless and odorless powder that is insoluble in water or alcohol. It consists of two types of molecules, the linear and helical amylose and the branched amylopectin, depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. Glycogen, the store of animals, is a more branched version of amylopectin. In industry, starch is converted into sugars, for example by malting and it is processed to produce many of the sugars used in processed foods. Dissolving starch in water gives wheatpaste, which can be used as a thickening, stiffening or gluing agent. The biggest industrial non-food use of starch is as an adhesive in the papermaking process, starch can be applied to parts of some garments before ironing, to stiffen them. The word starch is from a Germanic root with the strong, stiff. Amylum for starch is from the Greek αμυλον, amylon which means not ground at a mill, the root amyl is used in biochemistry for several compounds related to starch. Starch grains from the rhizomes of Typha as flour have been identified from grinding stones in Europe dating back to 30,000 years ago, starch grains from sorghum were found on grind stones in caves in Ngalue, Mozambique dating up to 100,000 years ago. Pure extracted wheat starch paste was used in Ancient Egypt possibly to glue papyrus, the extraction of starch is first described in the Natural History of Pliny the Elder around AD 77–79. Romans used it also in cosmetic creams, to powder the hair, persians and Indians used it to make dishes similar to gothumai wheat halva. Rice starch as surface treatment of paper has been used in production in China. In addition to starchy plants consumed directly,66 million tonnes of starch were being produced per year world-wide by 2008. In the EU this was around 8.5 million tonnes, with around 40% being used for applications and 60% for food uses. Most green plants use starch as their energy store, an exception is the family Asteraceae, where starch is replaced by the fructan inulin. In photosynthesis, plants use light energy to produce glucose from carbon dioxide, the glucose is used to make cellulose fibers, the structural component of the plant, or is stored in the form of starch granules, in amyloplasts
16.
Carbon
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Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature. Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
17.
Hydroxy group
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A hydroxy or hydroxyl group is the entity with the formula OH. It contains oxygen bonded to hydrogen, in organic chemistry, alcohol and carboxylic acids contain hydroxy groups. The anion, called hydroxide, consists of a hydroxy group, according to IUPAC rules, the term hydroxyl refers to the radical OH only, while the functional group −OH is called hydroxy group. Water, alcohols, carboxylic acids, and many other hydroxy-containing compounds can be deprotonated readily and this behavior is rationalized by the disparate electronegativities of oxygen and hydrogen. Hydroxy-containing compounds engage in hydrogen bonding, which causes them to stick together, organic compounds, which are often poorly soluble in water, become water soluble when they contain two or more hydroxy groups, as illustrated by sugars and amino acid. The hydroxy group is pervasive in chemistry and biochemistry, many inorganic compounds contain hydroxy groups, including sulfuric acid, the chemical compound produced on the largest scale industrially. Hydroxy groups participate in the reactions that link simple biological molecules into long chains. The joining of a fatty acid to glycerol to form a triacylglycerol removes the −OH from the end of the fatty acid. The joining of two aldehyde sugars to form a disaccharide removes the −OH from the group at the aldehyde end of one sugar. The creation of a bond to link two amino acids to make a protein removes the −OH from the carboxy group of one amino acid. Hydroxyl radicals are highly reactive and undergo chemical reactions that make them short-lived, when biological systems are exposed to hydroxyl radicals, they can cause damage to cells, including those in humans, where they react with DNA, lipids, and proteins. In 2009, Indias Chandrayaan-1 satellite, NASAs Cassini spacecraft and the Deep Impact probe have each detected the presence of water by evidence of hydroxyl fragments on the Moon. As reported by Richard Kerr, A spectrometer detected an infrared absorption at a wavelength of 3.0 micrometers that only water or hydroxyl—a hydrogen, NASA also reported in 2009 that the LCROSS probe revealed an ultraviolet emission spectrum consistent with hydroxyl presence. The Venus Express orbiter sent back Venus science data from April 2006 until December 2014, results from Venus Express include the detection of hydroxyl in the atmosphere. Hydronium Ion Oxide Reece, Jane, Urry, Lisa, Cain, Michael, Wasserman, Steven, Minorsky, Peter, Jackson, berge, Susan, Golden, Brandy, Triglia, Logan
18.
Chirality (chemistry)
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Chirality /kaɪˈrælɪti/ is a geometric property of some molecules and ions. A chiral molecule/ion is non-superposable on its mirror image, the presence of an asymmetric carbon center is one of several structural features that induce chirality in organic and inorganic molecules. The term chirality is derived from the Greek word for hand, the mirror images of a chiral molecule/ion are called enantiomers or optical isomers. Individual enantiomers are often designated as either right- or left-handed, Chirality is an essential consideration when discussing the stereochemistry in organic and inorganic chemistry. The concept is of practical importance because most biomolecules and pharmaceuticals are chiral. Chirality is based on molecular symmetry elements, specifically, a chiral compound can contain no improper axis of rotation, which includes planes of symmetry and inversion center. Chiral molecules are always dissymmetric but not always asymmetric, in general, chiral molecules have point chirality at a single stereogenic atom, which has four different substituents. The two enantiomers of such compounds are said to have different absolute configurations at this center, the stereogenic atom is usually carbon, as in many biological molecules. However chirality can exist in any atom, including metals, phosphorus, Chiral nitrogen is equally possible, although the effects of nitrogen inversion can make many of these compounds impossible to isolate. While the presence of a stereogenic atom describes the great majority of cases, for instance it is not necessary for the chiral substance to have a stereogenic atom. Examples include 1-bromo-1-chloro-1-fluoroadamantane, methylethylphenyltetrahedrane, certain calixarenes and fullerenes, which have inherent chirality, the C2-symmetric species 1, 1-bi-2-naphthol,1, 3-dichloro-allene have axial chirality. -cyclooctene and many ferrocenes have planar chirality, when the optical rotation for an enantiomer is too low for practical measurement, the species is said to exhibit cryptochirality. Even isotopic differences must be considered when examining chirality, illustrative is the derivative of benzyl alcohol PhCHDOH is chiral. The S enantiomer has D = +0. 715°, many biologically active molecules are chiral, including the naturally occurring amino acids and sugars. In biological systems, most of these compounds are of the chirality, most amino acids are levorotatory. Typical naturally occurring proteins, made of L amino acids, are known as left-handed proteins, d-amino acids are very rare in nature and have only been found in small peptides attached to bacteria cell walls. The origin of this homochirality in biology is the subject of much debate, however, there is some suggestion that early amino acids could have formed in comet dust. Enzymes, which are chiral, often distinguish between the two enantiomers of a chiral substrate, one could imagine an enzyme as having a glove-like cavity that binds a substrate
19.
Isomer
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An isomer is a molecule with the same molecular formula as another molecule, but with a different chemical structure. That is, isomers contain the number of atoms of each element. Isomers do not necessarily share similar properties, unless they also have the functional groups. There are two forms of isomerism, structural isomerism and stereoisomerism. In structural isomers, sometimes referred to as constitutional isomers, the atoms, Structural isomers have different IUPAC names and may or may not belong to the same functional group. For example, two position isomers would be 2-fluoropropane and 1-fluoropropane, illustrated on the side of the diagram above. In skeletal isomers the main chain is different between the two isomers. This type of isomerism is most identifiable in secondary and tertiary alcohol isomers, tautomers are structural isomers that spontaneously interconvert with each other, even when pure. They have different chemical properties and, as a consequence, distinct reactions characteristic to each form are observed, if the interconversion reaction is fast enough, tautomers cannot be isolated from each other. An example is when they differ by the position of a proton, such as in keto/enol tautomerism, there is, however, another isomer of C3H8O that has significantly different properties, methoxyethane. Unlike the isomers of propanol, methoxyethane has an oxygen connected to two carbons rather than to one carbon and one hydrogen. Methoxyethane is an ether, not an alcohol, because it lacks a hydroxyl group, propadiene and propyne are examples of isomers containing different bond types. Propadiene contains two double bonds, whereas propyne contains one triple bond, in stereoisomers the bond structure is the same, but the geometrical positioning of atoms and functional groups in space differs. This class includes enantiomers which are non-superposable mirror-images of each other, and diastereomers, enantiomers always contain chiral centers and diastereomers often do, but there are some diastereomers that neither are chiral nor contain chiral centers. Another type of isomer, conformational isomers, may be rotamers, diastereomers, for example, ortho- position-locked biphenyl systems have enantiomers. E/Z isomers, which have restricted rotation at a bond, are configurational isomers. They are classified as diastereomers, whether or not they contain any chiral centers, e/Z notation depicts absolute stereochemistry, which is an unambiguous descriptor based on CIP priorities. Cis–trans isomers are used to describe any molecules with restricted rotation in the molecule, for molecules with C=C double bonds, these descriptors describe relative stereochemistry only based on group bulkiness or principal carbon chain, and so can be ambiguous
20.
Deoxyribose
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Deoxyribose, or more precisely 2-deoxyribose, is a monosaccharide with idealized formula H−−−3−H. Its name indicates that it is a sugar, meaning that it is derived from the sugar ribose by loss of an oxygen atom. Several isomers exist with the formula H−−−3−H, but in all the hydroxyl groups are on the same side in the Fischer projection. The term 2-deoxyribose may refer to either of two enantiomers, the biologically important D-2-deoxyribose and to the rarely encountered mirror image L-2-deoxyribose, D-2-deoxyribose is a precursor to the nucleic acid DNA. 2-deoxyribose is an aldopentose, that is, a monosaccharide with five carbon atoms, as a component of DNA, 2-deoxyribose derivatives have an important role in biology. The DNA molecule, which is the repository of genetic information in life, consists of a long chain of deoxyribose-containing units called nucleotides. In the standard nucleic acid nomenclature, a DNA nucleotide consists of a molecule with an organic base attached to the 1′ ribose carbon. The 5′ hydroxyl of each unit is replaced by a phosphate that is attached to the 3′ carbon of the deoxyribose in the preceding unit. The double-stranded DNA molecules are typically much longer than RNA molecules. The backbone of RNA and DNA are structurally similar, but RNA is single stranded, other biologically important derivatives of deoxyribose include mono-, di-, and triphosphates, as well as 3′-5′ cyclic monophosphates. Deoxyribose is generated from ribose 5-phosphate by enzymes called ribonucleotide reductases and these enzymes catalyse the deoxygenation process. It was discovered in 1929 by Phoebus Levene
21.
Chemical formula
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These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH
22.
Tetrose
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A tetrose is a monosaccharide with 4 carbon atoms. They have either an aldehyde group in position 1 or a ketone functional group in position 2. The aldotetroses have two chiral centers and so 4 different stereoisomers are possible, there are two naturally occurring stereoisomers, the enantiomers of erythrose and threose having the D configuration but not the L enantiomers. The ketotetroses have one chiral center and, therefore, two possible stereoisomers, erythrulose, again, only the D enantiomer is naturally occurring
23.
Pentose
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A pentose is a monosaccharide with five carbon atoms. Pentoses are organized into two groups, aldopentoses have an aldehyde functional group at position 1. Ketopentoses have a functional group in position 2 or 3. The aldopentoses have three chiral centers and therefore eight different stereoisomers are possible, the 2-ketopentoses have two chiral centers, and therefore four different stereoisomers are possible. The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl groups to form intramolecular hemiacetals and hemiketals. The resulting ring structure is related to furan, and is termed a furanose, the ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl group and the neighbouring carbon atom — yielding two distinct configurations. Ribose is a constituent of RNA, and the related deoxyribose of DNA, a polymer composed of pentose sugars is called a pentosan. The Tollens’ test for pentoses relies on reaction of the furfural with phloroglucinol to produce a compound with high molar absorptivity. Aniline acetate test, for distinguishing pentoses from other carbohydrates Pentose phosphate pathway Bials test Ribose
24.
Hexose
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In bio-organic chemistry, a hexose is a monosaccharide with six carbon atoms, having the chemical formula C6H12O6. Hexoses are classified by functional group, with aldohexoses having an aldehyde at position 1, the aldohexoses have four chiral centres for a total of 16 possible aldohexose stereoisomers. The D/L configuration is based on the orientation of the hydroxyl at position 5, the eight D-aldohexoses are, Of these D-isomers, all except D-altrose are naturally occurring. L-Altrose, however, has been isolated from strains of the bacterium Butyrivibrio fibrisolvens, a mnemonic for the aldohexoses is All Altruists Gladly Make Gum in Gallon Tanks, allose, altrose, glucose, mannose, gulose, idose, galactose, talose. At carbon 3, the first two are on the right, the two are on the left, and so on. At carbon 4, the first four are on the right, at carbon 5, all eight D-aldohexoses have the hydroxyl group on the right. This can be seen as binary counting to seven, where 0 stands for hydroxyl and 1 for hydrogen and it has been known since 1926 that 6-carbon aldose sugars form cyclic hemiacetals. The diagram below shows the forms for D-glucose and D-mannose. The numbered carbons in the forms correspond to the same numbered carbons in the hemiacetal forms. The formation of the hemiacetal causes carbon number 1, which is symmetric in the open-chain form and this means that both glucose and mannose each have two cyclic forms. In solution, both of these exist in equilibrium with the open-chain form, the open-chain form, however, does not crystallize. Hence the two cyclic forms become separable when they are crystallized, the ketohexoses have 3 chiral centres and therefore eight possible stereoisomers. Of these, only the four D-isomers are known to naturally, Only the naturally occurring hexoses are capable of being fermented by yeasts. The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl groups to form intramolecular hemiacetals and hemiketals. The resulting ring structure is related to pyran, and is termed a pyranose, the ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl group and the neighbouring carbon atom, yielding two distinct configurations. Hexose sugars can form dihexose sugars with a reaction to form a 1
25.
Ketose
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A ketose is a monosaccharide containing one ketone group per molecule. With three carbon atoms, dihydroxyacetone is the simplest of all ketoses and is the one having no optical activity. Ketoses can isomerize into an aldose when the group is located at the end of the molecule
26.
Mannoheptulose
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It is a heptose, a monosaccharide with seven carbon atoms. By blocking the enzyme hexokinase, it prevents glucose phosphorylation, as a result, the breakdown of glucose is inhibited. It is found as D-mannoheptulose in avocados, mannoheptulose has been reported to inhibit insulin secretion from pancreas. Because of its inhibition of glycolysis in vitro, it has been investigated as a novel nutraceuticals for weight management for dogs
27.
Aqueous solution
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An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending to the relevant chemical formula, for example, a solution of table salt, or sodium chloride, in water would be represented as Na+ + Cl−. The word aqueous means pertaining to, related to, similar to, as water is an excellent solvent and is also naturally abundant, it is a ubiquitous solvent in chemistry. Substances that are hydrophobic often do not dissolve well in water, an example of a hydrophilic substance is sodium chloride. Acids and bases are aqueous solutions, as part of their Arrhenius definitions, the ability of a substance to dissolve in water is determined by whether the substance can match or exceed the strong attractive forces that water molecules generate between themselves. If the substance lacks the ability to dissolve in water the molecules form a precipitate, reactions in aqueous solutions are usually metathesis reactions. Metathesis reactions are another term for double-displacement, that is, when a cation displaces to form a bond with the other anion. The cation bonded with the latter anion will dissociate and bond with the other anion, aqueous solutions that conduct electric current efficiently contain strong electrolytes, while ones that conduct poorly are considered to have weak electrolytes. Those strong electrolytes are substances that are ionized in water. Nonelectrolytes are substances that dissolve in water yet maintain their molecular integrity, examples include sugar, urea, glycerol, and methylsulfonylmethane. When writing the equations of reactions, it is essential to determine the precipitate. To determine the precipitate, one must consult a chart of solubility, soluble compounds are aqueous, while insoluble compounds are the precipitate. Remember that there may not always be a precipitate, when performing calculations regarding the reacting of one or more aqueous solutions, in general one must know the concentration, or molarity, of the aqueous solutions. Solution concentration is given in terms of the form of the prior to it dissolving. Metal ions in aqueous solution Solubility Dissociation Acid-base reaction theories Properties of water Zumdahl S.1997, 4th ed. Boston, Houghton Mifflin Company
28.
Carbonyl group
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In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom, C=O. It is common to several classes of compounds, as part of many larger functional groups. A compound containing a group is often referred to as a carbonyl compound. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex, the remainder of this article concerns itself with the organic chemistry definition of carbonyl, where carbon and oxygen share a double bond. A carbonyl group characterizes the types of compounds, Note that the most specific labels are usually employed. For example, ROR structures are known as acid anhydride rather than the more generic ester, other organic carbonyls are urea and the carbamates, the derivatives of acyl chlorides chloroformates and phosgene, carbonate esters, thioesters, lactones, lactams, hydroxamates, and isocyanates. Examples of inorganic compounds are carbon dioxide and carbonyl sulfide. A special group of compounds are 1, 3-dicarbonyl compounds that have acidic protons in the central methylene unit. Examples are Meldrums acid, diethyl malonate and acetylacetone, because oxygen is more electronegative than carbon, carbonyl compounds often have resonance structures which affect their reactivity. This relative electronegativity draws electron density away from carbon, increasing the bonds polarity, carbon can then be attacked by nucleophiles or a negatively charged part of another molecule. During the reaction, the double bond is broken. This reaction is known as addition-elimination or condensation, the electronegative oxygen also can react with an electrophile, for example a proton in an acidic solution or with Lewis acids to form an oxocarbenium ion. The polarity of oxygen also makes the alpha hydrogens of carbonyl compounds much more acidic than typical sp3 C-H bonds, for example, the pKa values of acetaldehyde and acetone are 16.7 and 19 respectively, while the pKa value of methane is extrapolated to be approximately 50. This is because a carbonyl is in resonance with an enol. The deprotonation of the enol with a base produces an enolate. Amides are the most stable of the carbonyl couplings due to their high resonance stabilization between the nitrogen-carbon and carbon-oxygen bonds, carbonyl groups can be reduced by reaction with hydride reagents such as NaBH4 and LiAlH4, with bakers yeast, or by catalytic hydrogenation. Ketones give secondary alcohols while aldehydes, esters and carboxylic acids give primary alcohols, carbonyls can be alkylated in nucleophilic addition reactions using organometallic compounds such as organolithium reagents, Grignard reagents, or acetylides. Carbonyls also may be alkylated by enolates as in aldol reactions, carbonyls are also the prototypical groups with vinylogous reactivity
29.
Functional group
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In organic chemistry, functional groups are specific groups of atoms or bonds within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of, however, its relative reactivity can be modified by other functional groups nearby. The atoms of functional groups are linked to other and to the rest of the molecule by covalent bonds. Any subgroup of atoms of a compound also may be called a radical, and if a covalent bond is broken homolytically, Functional groups can also be charged, e. g. in carboxylate salts, which turns the molecule into a polyatomic ion or a complex ion. Complexation and solvation is also caused by interactions of functional groups. In the common rule of thumb like dissolves like, it is the shared or mutually well-interacting functional groups give rise to solubility. For example, sugar dissolves in water because both share the functional group and hydroxyls interact strongly with each other. Combining the names of groups with the names of the parent alkanes generates what is termed a systematic nomenclature for naming organic compounds. In traditional nomenclature, the first carbon atom after the carbon that attaches to the group is called the alpha carbon, the second, beta carbon. IUPAC conventions call for numeric labeling of the position, e. g. 4-aminobutanoic acid, in traditional names various qualifiers are used to label isomers, for example isopropanol is an isomer is n-propanol. The following is a list of functional groups. In the formulas, the symbols R and R usually denote an attached hydrogen, or a side chain of any length. Functional groups, called hydrocarbyl, that only carbon and hydrogen. Each one differs in type of reactivity, there are also a large number of branched or ring alkanes that have specific names, e. g. tert-butyl, bornyl, cyclohexyl, etc. Hydrocarbons may form charged structures, positively charged carbocations or negative carbanions, examples are tropylium and triphenylmethyl cations and the cyclopentadienyl anion. Haloalkanes are a class of molecule that is defined by a carbon–halogen bond and this bond can be relatively weak or quite stable. In general, with the exception of fluorinated compounds, haloalkanes readily undergo nucleophilic substitution reactions or elimination reactions, the substitution on the carbon, the acidity of an adjacent proton, the solvent conditions, etc. all can influence the outcome of the reactivity. Compounds that contain nitrogen in this category may contain C-O bonds, compounds that contain sulfur exhibit unique chemistry due to their ability to form more bonds than oxygen, their lighter analogue on the periodic table
30.
Atom
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An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms, Atoms are very small, typical sizes are around 100 picometers. Atoms are small enough that attempting to predict their behavior using classical physics - as if they were billiard balls, through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior. Every atom is composed of a nucleus and one or more bound to the nucleus. The nucleus is made of one or more protons and typically a number of neutrons. Protons and neutrons are called nucleons, more than 99. 94% of an atoms mass is in the nucleus. The protons have an electric charge, the electrons have a negative electric charge. If the number of protons and electrons are equal, that atom is electrically neutral, if an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion. The electrons of an atom are attracted to the protons in a nucleus by this electromagnetic force. The number of protons in the nucleus defines to what chemical element the atom belongs, for example, the number of neutrons defines the isotope of the element. The number of influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the changes observed in nature. The idea that matter is made up of units is a very old idea, appearing in many ancient cultures such as Greece. The word atom was coined by ancient Greek philosophers, however, these ideas were founded in philosophical and theological reasoning rather than evidence and experimentation. As a result, their views on what look like. They also could not convince everybody, so atomism was but one of a number of competing theories on the nature of matter. It was not until the 19th century that the idea was embraced and refined by scientists, in the early 1800s, John Dalton used the concept of atoms to explain why elements always react in ratios of small whole numbers
31.
Aldehyde
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The group—without R—is the aldehyde group, also known as the formyl group. Aldehydes are common in organic chemistry, Aldehydes feature an sp2-hybridized, planar carbon center that is connected by a double bond to oxygen and a single bond to hydrogen. The C–H bond is not ordinarily acidic, because of resonance stabilization of the conjugate base, an α-hydrogen in an aldehyde is far more acidic, with a pKa near 15, compared to the acidity of a typical alkane. This acidification is attributed to the quality of the formyl center and the fact that the conjugate base. Related to, the group is somewhat polar. Aldehydes can exist in either the keto or the enol tautomer, keto-enol tautomerism is catalyzed by either acid or base. Usually the enol is the minority tautomer, but it is more reactive, the common names for aldehydes do not strictly follow official guidelines, such as those recommended by IUPAC, but these rules are useful. IUPAC prescribes the following nomenclature for aldehydes, Acyclic aliphatic aldehydes are named as derivatives of the longest carbon chain containing the aldehyde group, thus, HCHO is named as a derivative of methane, and CH3CH2CH2CHO is named as a derivative of butane. The name is formed by changing the suffix -e of the parent alkane to -al, so that HCHO is named methanal, in other cases, such as when a -CHO group is attached to a ring, the suffix -carbaldehyde may be used. Thus, C6H11CHO is known as cyclohexanecarbaldehyde, if the presence of another functional group demands the use of a suffix, the aldehyde group is named with the prefix formyl-. This prefix is preferred to methanoyl-, the word aldehyde was coined by Justus von Liebig as a contraction of the Latin alcohol dehydrogenatus. In the past, aldehydes were sometimes named after the corresponding alcohols, for example, the term formyl group is derived from the Latin word formica ant. This word can be recognized in the simplest aldehyde, formaldehyde, Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so, the volatile aldehydes have pungent odors. Aldehydes degrade in air via the process of autoxidation, the two aldehydes of greatest importance in industry, formaldehyde and acetaldehyde, have complicated behavior because of their tendency to oligomerize or polymerize. They also tend to hydrate, forming the geminal diol, the oligomers/polymers and the hydrates exist in equilibrium with the parent aldehyde. Aldehydes are readily identified by spectroscopic methods, using IR spectroscopy, they display a strong νCO band near 1700 cm−1. In their 1H NMR spectra, the formyl hydrogen center absorbs near δH =9 and this signal shows the characteristic coupling to any protons on the alpha carbon
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Aldose
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An aldose, like a ketose, is a monosaccharide that contains only one aldehyde group per molecule, whereas ketose contains a ketone group. The chemical formula takes the form Cnn, the simplest possible aldose is the diose glycolaldehyde, which only contains two carbon atoms. Because they have at least one carbon center, aldoses with three or more carbon atoms exhibit stereoisomerism. Aldoses containing stereogenic centers can exist in either a D- form or L- form, biological systems tend to recognize D-aldoses more than L-aldoses. Examples of aldose include glycolaldehyde, glyceraldehyde, erythrose, threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose, mannose, gulose, idose, talose, all of these examples contain one group of aldehyde. They only differ in numbers of carbons in carbon skeleton, all of these complex sugars serve an important role in biochemistry. An aldose differs from a ketose in that it has a group at the end of the carbon chain instead of in the middle. This allows ketoses and aldoses to be differentiated through Seliwanoffs test. In Seliwanoffs test, aldoses tend to react in a slow pace, with different color of production, aldoses can be differentiate from the ketoses. An aldose may isomerize to a ketose through the Lobry-de Bruyn-van Ekenstein transformation, aldose and ketose, although differ in structures, also perform in different roles. Aldoses tend to isomerise into ketoses
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Ketone
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In chemistry, a ketone /ˈkiːtoʊn/ is an organic compound with the structure RCR, where R and R can be a variety of carbon-containing substituents. Ketones and aldehydes are simple compounds that contain a carbonyl group and they are considered simple because they do not have reactive groups like −OH or −Cl attached directly to the carbon atom in the carbonyl group, as in carboxylic acids containing −COOH. Many ketones are known and many are of importance in industry. Examples include many sugars and the industrial solvent acetone, which is the smallest ketone, the word ketone is derived from Aketon, an old German word for acetone. According to the rules of IUPAC nomenclature, ketones are named by changing the suffix -ane of the parent alkane to -anone, the position of the carbonyl group is usually denoted by a number. For the most important ketones, however, traditional names are still generally used. The common names of ketones are obtained by writing separately the names of the two alkyl groups attached to the group, followed by ketone as a separate word. The names of the groups are written alphabetically. When the two groups are the same, the prefix di- is added before the name of alkyl group. The positions of other groups are indicated by Greek letters, the α-carbon being the adjacent to carbonyl group. If both alkyl groups in a ketone are the same then the ketone is said to be symmetrical, although used infrequently, oxo is the IUPAC nomenclature for a ketone functional group. Other prefixes, however, are also used, for some common chemicals, keto or oxo refer to the ketone functional group. The term oxo is used widely through chemistry, for example, it also refers to an oxygen atom bonded to a transition metal. The ketone carbon is often described as sp2 hybridized, a description that includes both their electronic and molecular structure, ketones are trigonal planar around the ketonic carbon, with C−C−O and C−C−C bond angles of approximately 120°. Ketones differ from aldehydes in that the group is bonded to two carbons within a carbon skeleton. In aldehydes, the carbonyl is bonded to one carbon and one hydrogen and are located at the ends of carbon chains, ketones are also distinct from other carbonyl-containing functional groups, such as carboxylic acids, esters and amides. The carbonyl group is polar because the electronegativity of the oxygen is greater than that for carbon, thus, ketones are nucleophilic at oxygen and electrophilic at carbon. Because the carbonyl group interacts with water by bonding, ketones are typically more soluble in water than the related methylene compounds
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Stereoisomerism
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Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms, but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, by definition, molecules that are stereoisomers of each other represent the same structural isomer. Enantiomers, also known as optical isomers, are two stereoisomers that are related to other by a reflection, They are mirror images of each other that are non-superimposable. Human hands are an analog of stereoisomerism. Every stereogenic center in one has the configuration in the other. As a result, different enantiomers of a compound may have different biological effects. Pure enantiomers also exhibit the phenomenon of optical activity and can be separated only with the use of a chiral agent, in nature, only one enantiomer of most chiral biological compounds, such as amino acids, is present. Diastereomers are stereoisomers not related through a reflection operation and they are not mirror images of each other. These include meso compounds, cis–trans isomers, and non-enantiomeric optical isomers, diastereomers seldom have the same physical properties. In the example shown below, the form of tartaric acid forms a diastereomeric pair with both levo and dextro tartaric acids, which form an enantiomeric pair. Please refer to Chirality for more regarding the D- and L- labels. Stereoisomerism about double bonds arises because rotation about the bond is restricted. The simplest examples of cis-trans isomerism are the 1, 2-disubstituted ethenes, molecule I is cis-1, 2-dichloroethene and molecule II is trans-1, 2-dichloroethene. Due to occasional ambiguity, IUPAC adopted a rigorous system wherein the substituents at each end of the double bond are assigned priority based on their atomic number. If the high-priority substituents are on the side of the bond. If they are on sides, it is E. Since chlorine has an atomic number than hydrogen, it is the highest-priority group. Using this notation to name the above pictured molecules, molecule I is -1, 2-dichloroethene and molecule II is -1 and it is not the case that Z and cis or E and trans are always interchangeable
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Covalent bond
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A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, for many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration. Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, the term covalent bond dates from 1939. In the molecule H2, the atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar electronegativities, thus, covalent bonding does not necessarily require that the two atoms be of the same elements, only that they be of comparable electronegativity. Covalent bonding that entails sharing of electrons more than two atoms is said to be delocalized. The term covalence in regard to bonding was first used in 1919 by Irving Langmuir in a Journal of the American Chemical Society article entitled The Arrangement of Electrons in Atoms and Molecules. Langmuir wrote that we shall denote by the term covalence the number of pairs of electrons that an atom shares with its neighbors. The idea of covalent bonding can be traced several years before 1919 to Gilbert N. Lewis and he introduced the Lewis notation or electron dot notation or Lewis dot structure, in which valence electrons are represented as dots around the atomic symbols. Pairs of electrons located between atoms represent covalent bonds, multiple pairs represent multiple bonds, such as double bonds and triple bonds. An alternative form of representation, not shown here, has bond-forming electron pairs represented as solid lines, Lewis proposed that an atom forms enough covalent bonds to form a full outer electron shell. In the diagram of methane shown here, the atom has a valence of four and is, therefore, surrounded by eight electrons, four from the carbon itself. Each hydrogen has a valence of one and is surrounded by two electrons – its own one electron plus one from the carbon, walter Heitler and Fritz London are credited with the first successful quantum mechanical explanation of a chemical bond in 1927. Their work was based on the valence bond model, which assumes that a bond is formed when there is good overlap between the atomic orbitals of participating atoms. Atomic orbitals have specific directional properties leading to different types of covalent bonds, sigma bonds are the strongest covalent bonds and are due to head-on overlapping of orbitals on two different atoms. A single bond is usually a σ bond, pi bonds are weaker and are due to lateral overlap between p orbitals. A double bond between two given atoms consists of one σ and one π bond, and a bond is one σ. Covalent bonds are also affected by the electronegativity of the atoms which determines the chemical polarity of the bond
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Dihydroxyacetone
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Dihydroxyacetone /ˌdaɪhaɪˌdrɒksiˈæsᵻtoʊn/, or DHA, also known as glycerone, is a simple carbohydrate with formula C 3H 6O3. DHA is primarily used as an ingredient in sunless tanning products and it is often derived from plant sources such as sugar beets and sugar cane, and by the fermentation of glycerin. DHA is a white crystalline powder. It has a sweet cooling taste and a characteristic odor and it is the simplest of all ketoses and has no chiral center or optical activity. The normal form is a dimer which is soluble in one part water and 15 parts ethanol. When freshly prepared, it rapidly to the monomer in solution. The monomer is very soluble in water, ethanol, diethyl ether, DHA may be prepared, along with glyceraldehyde, by the mild oxidation of glycerol, for example with hydrogen peroxide and a ferrous salt as catalyst. It can also be prepared in high yield and selectivity at room temperature from glycerol using cationic palladium-based catalysts with oxygen, glyceraldehyde is a structural isomer of dihydroxyacetone. Its phosphorylated form, dihydroxyacetone phosphate, takes part in glycolysis, DHA was first recognized as a skin coloring agent by German scientists in the 1920s. Through its use in the X-ray process, it was noted as causing the surface to turn brown when spilled. In the 1950s, Eva Wittgenstein at the University of Cincinnati did further research with dihydroxyacetone and her studies involved using DHA as an oral drug for assisting children with glycogen storage disease. The children received large doses of DHA by mouth, and sometimes spat or spilled the substance onto their skin, healthcare workers noticed that the skin turned brown after a few hours of DHA exposure. Eva Wittgenstein continued to experiment with DHA, painting liquid solutions of it onto her own skin and she was able to consistently reproduce the pigmentation effect, and noted that DHA did not appear to penetrate beyond the stratum corneum, or dead skin surface layer. Research then continued on DHAs skin coloring effect in relation to treatment for patients suffering from vitiligo and this skin browning effect is non-toxic, and similar to the Maillard reaction. DHA reacts chemically with the acids in the protein keratin the major component of the skin surface. Different amino acids react to DHA in different ways, producing different tones of coloration from yellow to brown, the resulting pigments are called melanoidins. These are similar in coloration to melanin, the substance in the deeper skin layers which brown or tan. Both acetic acid bacteria A. aceti and G. oxydans use glycerol as a source to form dihydroxyacetone
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Glyceraldehyde
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Glyceraldehyde is a triose monosaccharide with chemical formula C3H6O3. It is the simplest of all common aldoses and it is a sweet, colorless, crystalline solid that is an intermediate compound in carbohydrate metabolism. The word comes from combining glycerol and aldehyde, as glyceraldehyde is glycerol with one hydroxymethyl group oxidized to an aldehyde, the stereochemical configuration can only be determined from the chemical structure, whereas the optical rotation can only be determined empirically. It was by a lucky guess that the molecular d- geometry was assigned to -glyceraldehyde in the late 19th century, in the d/l system, glyceraldehyde is used as the configurational standard for carbohydrates. Monosaccharides with an absolute configuration identical to -glyceraldehyde at the last stereocentre and those similar to -glyceraldehyde are assigned an l-. Glyceraldehyde can be prepared, along with dihydroxyacetone, by the oxidation of glycerol, for example with hydrogen peroxide. Dihydroxyacetone, the simplest ketose, is an isomer of glyceraldehyde, the enzyme glycerol dehydrogenase has two substrates, glycerol and NADP+, and 3 products, D-glyceraldehyde, NADPH and H+. The interconversion of the phosphates of glyceraldehyde and dihydroxyacetone, catalyzed by the enzyme triosephosphate isomerase, is an important intermediate step in glycolysis
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Fischer projection
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The Fischer projection, devised by Hermann Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates and used by chemists, the use of Fischer projections in non-carbohydrates is discouraged, as such drawings are ambiguous when confused with other types of drawing. All nonterminal bonds are depicted as horizontal or vertical lines, the carbon chain is depicted vertically, with carbon atoms represented by the center of crossing lines. The orientation of the chain is so that the C1 carbon is at the top. In an aldose, the carbon of the group is C1. A Fischer projection is used to differentiate between L- and D- molecules, on a Fischer projection, the penultimate carbon of D sugars are depicted with hydrogen on the left and hydroxyl on the right. L sugars will be shown with the hydrogen on the right, in a Fischer projection, all horizontal bonds project toward the viewer, while vertical bonds project away from the viewer. However, any rotation of 180° doesnt change the molecules representation, swapping two pairs of groups attached to the central carbon atom still represents the same molecule as was represented by the original Fischer projection. However this does not alter the Fischer projections for any previous carbons, according to IUPAC rules, all hydrogen atoms should preferably be drawn explicitly, in particular, the hydrogen atoms of the end group of carbohydrates should be present. In this regard Fischer projection is different from skeletal formulae, Fischer projections are most commonly used in biochemistry and organic chemistry to represent monosaccharides, but can also be used for amino acids or for other organic molecules. Since Fischer projections depict the stereochemistry of a molecule, they are useful for differentiating between enantiomers of chiral molecules. Haworth projections are a related chemical used to represent sugars in ring form. The groups on the hand side of a Fischer projection are equivalent to those below the plane of the ring in Haworth projections. Fischer projections should not be confused with Lewis structures, which do not contain any information about three dimensional geometry, Newman projections are normally used to represent the stereochemistry of alkanes. Cahn-Ingold-Prelog priority rule Chair conformation Haworth projection Newman projection Natta projection
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Skeletal formula
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A skeletal formula shows the skeletal structure or skeleton of a molecule, which is composed of the skeletal atoms that make up the molecule. It is represented in two dimensions, as on a page of paper and it employs certain conventions to represent carbon and hydrogen atoms, which are the most common in organic chemistry. The technique was developed by the organic chemist Friedrich August Kekulé von Stradonitz, Skeletal formulae have become ubiquitous in organic chemistry, partly because they are relatively quick and simple to draw. As in a Lewis structure, a doubled or tripled line segment indicates double or triple bonding, the skeletal structure of an organic compound is the series of atoms bonded together that form the essential structure of the compound. The skeleton can consist of chains, branches and/or rings of bonded atoms, Skeletal atoms other than carbon or hydrogen are called heteroatoms. The skeleton has hydrogen and/or various substituents bonded to its atoms, hydrogen is the most common non-carbon atom that is bonded to carbon and, for simplicity, is not explicitly drawn. For example, in the image below, the formula of hexane is shown. The carbon atom labeled C1 appears to have one bond. The carbon atom labelled C3 has two bonds to other carbons and is bonded to two hydrogen atoms as well. NOTE, It doesnt matter which end of the chain you start numbering from, the condensed formula or the IUPAC name will confirm the orientation. Some molecules will become familiar regardless of the orientation, any hydrogen atoms bonded to non-carbon atoms are drawn explicitly. In ethanol, C2H5OH, for instance, the hydrogen bonded to oxygen is denoted by the symbol H. Lines representing heteroatom-hydrogen bonds are usually omitted for clarity and compactness and these bonds are sometimes drawn out in full in order to accentuate their presence when they participate in reaction mechanisms. Shown below for comparison are a model of the actual three-dimensional structure of the ethanol molecule in the gas phase, the Lewis structure. All atoms that are not carbon or hydrogen are signified by their symbol, for instance Cl for chlorine, O for oxygen, Na for sodium. These atoms are known as heteroatoms in the context of organic chemistry. There are also symbols that appear to be chemical element symbols and these are known as pseudoelement symbols or organic elements. The most widely used symbol is Ph, which represents the phenyl group, boc for the t-butoxycarbonyl group Cbz or Z for the carboxybenzyl group Fmoc for the fluorenylmethoxycarbonyl group Two atoms can be bonded by sharing more than one pair of electrons
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Monosaccharide nomenclature
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The elementary formula of a simple monosaccharide is CnH2nOn, where the integer n is at least 3 and rarely greater than 7. Simple monosaccharides may be named generically according on the number of carbon atoms n, trioses, tetroses, pentoses, hexoses, the carbons of the chain are conventionally numbered from 1 to n, starting from the end which is closest to the carbonyl. If the carbonyl is at the beginning of the chain. These names can be combined with the chain length prefix, as in aldohexose or ketopentose, most ketoses found in nature have the carbonyl in position 2, when that is not the case, one uses a numeric prefix to indicate the carbonyls position. Thus for example, aldohexose means H5H, ketopentose means H3H, an alternative nomenclature uses the suffix -ose only for aldoses, and -ulose for ketoses. The position of the carbonyl is indicated by a numerical infix, for example, hexose in this nomenclature means H5H, pentulose means H3H, and hexa-3-ulose means H23H. Open-chain monosaccharides with same molecular graph may exist as two or more stereoisomers, the Fischer projection is a systematic way of drawing the skeletal formula of an open-chain monosaccharide so that each stereoisomer is uniquely identified. Two isomers whose molecules are mirror-images of each other are identified by prefixes D- or L-, according to the handedness of the chiral carbon atom that is farthest from the carbonyl. In the Fischer projection, that is the carbon from the bottom. If the molecular graph is symmetrical and the two halves are mirror images of other, then the molecule is identical to its mirror image. A distinct common name, such as glucose or ribose, is assigned to each pair of mirror-image stereoisomers. These names have standard three-letter abbreviations, such as Glc for glucose and these prefixes are attached to the systematic name of the molecular graph. So for example, D-glucose is D-gluco-hexose, D-ribose is D-ribo-pentose, note that, in this nomenclature, mirror-image isomers differ only in the D/L prefix, even though all their hydroxyls are reversed. The following tables shows the Fischer projections of selected monosaccharides, with their conventional names, the table shows all aldoses with 3 to 6 carbon atoms, and a few ketoses. For chiral molecules, only the D- form is shown, the forms have mirror-image structures. Some of these monosaccharides are only prepared in the laboratory. For monosaccharides in their form, an infix is placed before the -ose, -ulose. The infix is furan for a 5-atom ring, pyran for 6, septan for 7, ring closure creates another chiral center at the anomeric carbon, and therefore each open-chain stereoisomer gives rise to two distinct stereoisomers
