A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, biochemistry, the term molecule is used less also being applied to polyatomic ions. In the kinetic theory of gases, the term molecule is used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are monatomic molecules. A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with oxygen. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are not considered single molecules. Molecules as components of matter are common in organic substances, they make up most of the oceans and atmosphere. However, the majority of familiar solid substances on Earth, including most of the minerals that make up the crust and core of the Earth, contain many chemical bonds, but are not made of identifiable molecules.
No typical molecule can be defined for ionic crystals and covalent crystals, although these are composed of repeating unit cells that extend either in a plane or three-dimensionally. The theme of repeated unit-cellular-structure holds for most condensed phases with metallic bonding, which means that solid metals are not made of molecules. In glasses, atoms may be held together by chemical bonds with no presence of any definable molecule, nor any of the regularity of repeating units that characterizes crystals; the science of molecules is called molecular chemistry or molecular physics, depending on whether the focus is on chemistry or physics. Molecular chemistry deals with the laws governing the interaction between molecules that results in the formation and breakage of chemical bonds, while molecular physics deals with the laws governing their structure and properties. In practice, this distinction is vague. In molecular sciences, a molecule consists of a stable system composed of two or more atoms.
Polyatomic ions may sometimes be usefully thought of as electrically charged molecules. The term unstable molecule is used for reactive species, i.e. short-lived assemblies of electrons and nuclei, such as radicals, molecular ions, Rydberg molecules, transition states, van der Waals complexes, or systems of colliding atoms as in Bose–Einstein condensate. According to Merriam-Webster and the Online Etymology Dictionary, the word "molecule" derives from the Latin "moles" or small unit of mass. Molecule – "extremely minute particle", from French molécule, from New Latin molecula, diminutive of Latin moles "mass, barrier". A vague meaning at first; the definition of the molecule has evolved. Earlier definitions were less precise, defining molecules as the smallest particles of pure chemical substances that still retain their composition and chemical properties; this definition breaks down since many substances in ordinary experience, such as rocks and metals, are composed of large crystalline networks of chemically bonded atoms or ions, but are not made of discrete molecules.
Molecules are held together by ionic bonding. Several types of non-metal elements exist only as molecules in the environment. For example, hydrogen only exists as hydrogen molecule. A molecule of a compound is made out of two or more elements. A covalent bond is a chemical bond; these electron pairs are termed shared pairs or bonding pairs, the stable balance of attractive and repulsive forces between atoms, when they share electrons, is termed covalent bonding. Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions, is the primary interaction occurring in ionic compounds; the ions are atoms that have lost one or more electrons and atoms that have gained one or more electrons. This transfer of electrons is termed electrovalence in contrast to covalence. In the simplest case, the cation is a metal atom and the anion is a nonmetal atom, but these ions can be of a more complicated nature, e.g. molecular ions like NH4+ or SO42−. An ionic bond is the transfer of electrons from a metal to a non-metal for both atoms to obtain a full valence shell.
Most molecules are far too small to be seen with the naked eye. DNA, a macromolecule, can reach macroscopic sizes, as can molecules of many polymers. Molecules used as building blocks for organic synthesis have a dimension of a few angstroms to several dozen Å, or around one billionth of a meter. Single molecules cannot be observed by light, but small molecules and the outlines of individual atoms may be traced in some circumstances by use of an atomic force microscope; some of the largest molecules are supermolecules. The smallest molecule is the diatomic hydrogen, with a bond length of 0.74 Å. Effective molecular radius is the size; the table of permselectivity for different substances contains examples. The chemical formula for a molecule uses one line of chemical element symbols and sometimes al
Ullmann's Encyclopedia of Industrial Chemistry
Ullmann's Encyclopedia of Industrial Chemistry is a reference work related to industrial chemistry published in English and German. As of 2016 it is in its 7th edition; the first edition was published in German by Fritz Ullmann in 1914. The 4th Edition, published 1972 to 1984 contained 25 volumes; the fifth edition, published 1985 to 1996, was the first version available in English. In 1997, the first online version was available, updated at least every other month; as of 2016, Ullmann's Encyclopedia is in 40 volumes including one index volume. While PDF versions of individual chapters used to be available for purchase from the Wiley Online Library, as of at least 9/2018, it appears that Wiley has restricted access to the online version only to institutional users. Therefore, it is no longer possible to purchase individual chapters through the Wiley Online Library. For individuals or small companies, the only option is to purchase the entire hardcopy 40-volume set for $11,150. Industrial chemistry is the study of chemistry with a higher mathematics and physics education for critical processes engineering and maintenance.
The industrial chemist strengthens the association of new materials investigation and manufacturing development, amid research chemistry and chemical engineering, through innovative intelligence and quality management. Subject areas include "inorganic and organic chemicals, pharmaceuticals and plastics, metals and alloys and biotechnological products, food chemistry, process engineering and unit operations, analytical methods, environmental protection and others"; as of 2016, Barbara Elvers is Editor-in-Chief and the editorial board consists of 17 editors, all but 3 of them from Germany
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar and non-specialty grout. It was developed from other types of hydraulic lime in England in the mid 19th century, originates from limestone, it is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, adding 2 to 3 percent of gypsum. Several types of Portland cement are available; the most common, called ordinary Portland cement, is grey, but white Portland cement is available. Its name is derived from its similarity to Portland stone, quarried on the Isle of Portland in Dorset, England, it was named by Joseph Aspdin who obtained a patent for it in 1824. However, his son William Aspdin is regarded as the inventor of "modern" Portland cement due to his developments in the 1840s. Portland cement is caustic, so it can cause chemical burns; the powder can cause irritation or, with severe exposure, lung cancer, can contain some hazardous components, such as crystalline silica and hexavalent chromium.
Environmental concerns are the high energy consumption required to mine and transport the cement, the related air pollution, including the release of greenhouse gases, dioxin, NOx, SO2, particulates. The production of Portland cement contributes to about 10% of world carbon dioxide emission. To meet the rising global population, the International Energy Agency estimated that the cement production is set to increase between 12 to 23% by 2050. There are several ongoing researches targeting a suitable replacement of Portland cement by supplementary cementitious materials; the low cost and widespread availability of the limestone and other naturally-occurring materials used in Portland cement make it one of the lowest-cost materials used over the last century. Concrete produced from Portland cement is one of the world's most versatile construction materials. Portland cement was developed from natural cements made in Britain beginning in the middle of the 18th century, its name is derived from its similarity to Portland stone, a type of building stone quarried on the Isle of Portland in Dorset, England.
The development of modern Portland cement began in 1756, when John Smeaton experimented with combinations of different limestones and additives, including trass and pozzolanas, relating to the planned construction of a lighthouse, now known as Smeaton's Tower. In the late 18th century, Roman cement was patented in 1796 by James Parker. Roman cement became popular, but was replaced by Portland cement in the 1850s. In 1811, James Frost produced a cement. James Frost is reported to have erected a manufactory for making of an artificial cement in 1826. In 1811 Edgar Dobbs of Southwark patented a cement of the kind invented 7 years by the French engineer Louis Vicat. Vicat's cement is an artificial hydraulic lime, is considered the'principal forerunner' of Portland cement; the name Portland cement is recorded in a directory published in 1823 being associated with a William Lockwood and others. In his 1824 cement patent, Joseph Aspdin called his invention "Portland cement" because of the its resemblance to Portland stone.
However, Aspdin's cement was nothing like modern Portland cement, but was a first step in the development of modern Portland cement, has been called a'proto-Portland cement'. William Aspdin had left his father's company. In the 1840's William Aspdin accidentally, produced calcium silicates which are a middle step in the development of Portland cement. In 1848, William Aspdin further improved his cement. In 1853, he moved to Germany, where he was involved in cement making. William Aspdin made what could be called'meso-Portland cement'. Isaac Charles Johnson further refined the production of'meso-Portland cement', claimed to be the real father of Portland cement. John Grant of the Metropolitan Board of Works in 1859 set out requirements for cement to be used in the London sewer project; this became a specification for Portland cement. The next development in the manufacture of Portland cement was the introduction of the rotary kiln, patented by Frederick Ransome in 1885 and 1886; the Hoffmann'endless' kiln, said to give'perfect control over combustion' was tested in 1860, showed the process produced a better grade of cement.
This cement was made at the Portland Cementfabrik Stern at Stettin, the first to use a Hoffmann kiln.. The Association of German Cement Manufacturers issued a standard on Portland cement in 1878. Portland cement had been imported into the United States from Germany and England, in the 1870s and 1880s, it was being produced by Eagle Portland cement near Kalamazoo, in 1875, the first Portland cement was produced in the Coplay Cement Company Kilns under the direction of David O. Saylor in Coplay, Pennsylvania. By the early 20th century, American-made Portland cement had displaced most of the imported Portland cement. ASTM C150 defines Portland cement as'hydraulic cement produced by pulverizing clinkers which consist of hydraulic calcium silicates containing one or more of the forms of calcium sulfate as an inter ground addition'; the European Standard EN 197-1 uses the following definition: Portland cement clinker is a hydraulic material which shall consist of at l
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula CnH2n−2. Alkynes are traditionally known as acetylenes, although the name acetylene refers to C2H2, known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are hydrophobic but tend to be more reactive. Alkynes are characteristically more unsaturated than alkenes, thus they add two equivalents of bromine. Other reactions are listed below. In some reactions, alkynes are less reactive than alkenes. For example, in a molecule with an -ene and an -yne group, addition occurs preferentially at the -ene. Possible explanations involve the two π-bonds in the alkyne delocalising, which would reduce the energy of the π-system or the stability of the intermediates during the reaction, they show greater tendency to oligomerize than alkenes do.
The resulting polymers, called polyacetylenes are conjugated and can exhibit semiconducting properties. In acetylene, the H–C≡C bond angles are 180°. By virtue of this bond angle, alkynes are rod-like. Correspondingly, cyclic alkynes are rare. Benzyne is unstable; the C≡C bond distance of 121 picometers is much shorter than the C=C distance in alkenes or the C–C bond in alkanes. The triple bond is strong with a bond strength of 839 kJ/mol; the sigma bond contributes 369 kJ/mol, the first pi bond contributes 268 kJ/mol and the second pi-bond of 202 kJ/mol bond strength. Bonding discussed in the context of molecular orbital theory, which recognizes the triple bond as arising from overlap of s and p orbitals. In the language of valence bond theory, the carbon atoms in an alkyne bond are sp hybridized: they each have two unhybridized p orbitals and two sp hybrid orbitals. Overlap of an sp orbital from each atom forms one sp–sp sigma bond; each p orbital on one atom overlaps one on the other atom, forming two pi bonds, giving a total of three bonds.
The remaining sp orbital on each atom can form a sigma bond to another atom, for example to hydrogen atoms in the parent acetylene. The two sp orbitals project on opposite sides of the carbon atom. Internal alkynes feature carbon substituents on each acetylenic carbon. Symmetrical examples include 3-hexyne. Terminal alkynes have the formula RC2H. An example is methylacetylene. Terminal alkynes, like acetylene itself, are mildly acidic, with pKa values of around 25, they are far more acidic than alkenes and alkanes, which have pKa values of around 40 and 50, respectively. The acidic hydrogen on terminal alkynes can be replaced by a variety of groups resulting in halo-, silyl-, alkoxoalkynes; the carbanions generated by deprotonation of terminal alkynes are called acetylides. In systematic chemical nomenclature, alkynes are named with the Greek prefix system without any additional letters. Examples include octyne. In parent chains with four or more carbons, it is necessary to say. For octyne, one can either write oct-3-yne when the bond starts at the third carbon.
The lowest number possible is given to the triple bond. When no superior functional groups are present, the parent chain must include the triple bond if it is not the longest possible carbon chain in the molecule. Ethyne is called by its trivial name acetylene. In chemistry, the suffix -yne is used to denote the presence of a triple bond. In organic chemistry, the suffix follows IUPAC nomenclature. However, inorganic compounds featuring unsaturation in the form of triple bonds may be denoted by substitutive nomenclature with the same methods used with alkynes. "-diyne" is used when there are two triple bonds, so on. The position of unsaturation is indicated by a numerical locant preceding the "-yne" suffix, or'locants' in the case of multiple triple bonds. Locants are chosen. "-yne" is used as an infix to name substituent groups that are triply bound to the parent compound. Sometimes a number between hyphens is inserted before it to state which atoms the triple bond is between; this suffix arose as a collapsed form of the end of the word "acetylene".
The final" - e" disappears. Commercially, the dominant alkyne is acetylene itself, used as a fuel and a precursor to other compounds, e.g. acrylates. Hundreds of millions of kilograms are produced annually by partial oxidation of natural gas: 2 CH4 + 3/2 O2 → HC≡CH + 3 H2OPropyne industrially useful, is prepared by thermal cracking of hydrocarbons. Most other industrially useful alkyne derivatives are prepared from acetylene, e.g. via condensation with formaldehyde. Specialty alkynes are prepared by dehydrohalogenation of vicinal alkyl dihalides or vinyl halides. Metal acetylides can be coupled with primary alkyl halides. Via the Fritsch–Buttenberg–Wiechell rearrangement, alkynes are prepared from vinyl bromides. Alkynes can be prepared from aldehydes using the Corey–Fuchs reaction and from aldehydes or ketones by the Seyferth–Gilbert homologation. In the alkyne zipper reaction, alkynes are generated from other alkynes by treatment with a strong base. Featuring a reactive functional group, alkynes participate in many organic reactions.
Such use was pioneered by Ralph Raphael, who in 1955 wrote the first book describing their versatility as intermediates in synthesis. Alkynes character
Organosulfates are a class of organic compounds sharing a common functional group with the structure R-O-SO3−. The SO4 core is a sulfate group and the R group is any organic residue. All organosulfates are formally esters derived from alcohols and sulfuric acid, although many are not prepared in this way. Many sulfate esters are used in detergents, some are useful reagents. Alkyl sulfates consist of a hydrophobic hydrocarbon chain, a polar sulfate group and either a cation or amine to neutralize the sulfate group. Examples include: related potassium and ammonium salts. Alkyl sulfates are used as an anionic surfactant in liquid soaps, detergents to clean wool, surface cleaners, as active ingredients in laundry detergents and conditioners, they can be found in other household products such as toothpastes, antacids and foods. They are found in consumer products at concentrations ranging from 3-20%. In 2003 118,000 t/a of alkyl sulfates were used in the U. S. A common example is sodium lauryl sulfate, with the formula CH311OSO3Na.
Common in consumer products are the sulfate esters of ethoxylated fatty alcohols such as those derived from lauryl alcohol. An example is an ingredient in some cosmetics. Alkylsulfate can be produced from alcohols, which in turn are obtained by hydrogenation of animal or vegetable oils and fats or using the Ziegler process or through oxo synthesis. If produced from oleochemical feedstock or the Ziegler process, the hydrocarbon chain of the alcohol will be linear. If derived using the oxo process, a low level of branching will appear with a methyl or ethyl group at the C-2 position and odd amounts of alkyl chains; these alcohols react with chlorosulfuric acid: ClSO3H + ROH → ROSO3H + HClSome organosulfates can be prepared by the Elbs persulfate oxidation of phenols and the Boyland–Sims oxidation of anilines. A less common family of organosulfates have the formula R-O-SO2-O-R', they are prepared from the alcohol. The main examples are diethyl sulfate and dimethyl sulfate, colourless liquids that are used as reagents in organic synthesis.
These compounds are dangerous alkylating agents. The reduction of sulfate in nature involves the formation of one or sometimes two sulfate esters, adenosine 5'-phosphosulfate and 3'-phosphoadenosine-5'-phosphosulfate. Sulfate is an inert anion, so nature activates it by the formation of these ester derivatives, which are susceptible to reduction to sulfite. Many organisms utilize these reactions for metabolic purposes or for the biosynthesis of sulfur compounds required for life; because they are used in commercial products, the safety aspects of organosulfates are investigated. Alkyl sulfates if ingested are well-absorbed and are metabolized into a C3, C4 or C5 sulfate and an additional metabolite; the highest irritant of the alkyl sulfates is sodium laurylsulfate, with the threshold before irritation at a concentration of 20%. Surfactants in consumer products are mixed, reducing likelihood of irritation. According to OECD TG 406, alkyl sulfates in animal studies were not found to be skin sensitizers.
Laboratory studies have not found alkyl sulfates to be mutagenic or carcinogenic. No long-term reproductive effects have been found; the primary disposal of alkyl sulfate from used commercial products is wastewater. The concentration of alkylsulfates in effluent from waste water treatment plants has been measured at 10 micrograms per litre and lower. Alkyl sulfates biodegrade even starting before reaching the WWTP. Once at the treatment plant, they are removed by biodegradation. Invertebrates were found to be the most-sensitive trophic group to alkyl sulfates. Sodium laurylsulfate tested on Uronema parduczi, a protozoan, was found to have the lowest effect value with the 20 h-EC5 being 0.75 milligrams per litre. Chronic exposure tests with C12 to C18 with the invertebrate Ceriodaphnia dubia found the highest toxicity is with C14. In terms of thermal stability, alkyl sulfates degrade well before reaching their boiling point due to low vapor pressure. Soil sorption is proportional to carbon chain length, with a length of 14 and more having the highest sorption rate.
Soil concentrations have been found to vary from 0.0035 to 0.21 milligrams per kilogram dw
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In the context of food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage; the science of fermentation is known as zymology. In microorganisms, fermentation is the primary means of producing ATP by the degradation of organic nutrients anaerobically. Humans have used fermentation to produce beverages since the Neolithic age. For example, fermentation is used for preservation in a process that produces lactic acid found in such sour foods as pickled cucumbers and yogurt, as well as for producing alcoholic beverages such as wine and beer. Fermentation occurs within the gastrointestinal tracts including humans. Below are some definitions of fermentation, they range from general usages to more scientific definitions.
Preservation methods for food via microorganisms. Any process that produces alcoholic beverages or acidic dairy products. Any large-scale microbial process occurring with or without air. Any energy-releasing metabolic process that takes place only under anaerobic conditions. Any metabolic process that releases energy from a sugar or other organic molecule, does not require oxygen or an electron transport system, uses an organic molecule as the final electron acceptor. Along with photosynthesis and aerobic respiration, fermentation is a way of extracting energy from molecules, but it is the only one common to all bacteria and eukaryotes, it is therefore considered the oldest metabolic pathway, suitable for an environment that does not yet have oxygen. Yeast, a form of fungus, occurs in any environment capable of supporting microbes, from the skins of fruits to the guts of insects and mammals and the deep ocean, they harvest sugar-rich materials to produce ethanol and carbon dioxide; the basic mechanism for fermentation remains present in all cells of higher organisms.
Mammalian muscle carries out the fermentation that occurs during periods of intense exercise where oxygen supply becomes limited, resulting in the creation of lactic acid. In invertebrates, fermentation produces succinate and alanine. Fermentative bacteria play an essential role in the production of methane in habitats ranging from the rumens of cattle to sewage digesters and freshwater sediments, they produce hydrogen, carbon dioxide and acetate and carboxylic acids. Acetogenic bacteria oxidize the acids, obtaining more acetate and either formate. Methanogens convert acetate to methane. Fermentation reacts NADH with an organic electron acceptor; this is pyruvate formed from sugar through glycolysis. The reaction produces NAD+ and an organic product, typical examples being ethanol, lactic acid, carbon dioxide, hydrogen gas. However, more exotic compounds can be produced by fermentation, such as butyric acetone. Fermentation products contain chemical energy, but are considered waste products, since they cannot be metabolized further without the use of oxygen.
Fermentation occurs in an anaerobic environment. In the presence of O2, NADH, pyruvate are used to generate ATP in respiration; this is called oxidative phosphorylation, it generates much more ATP than glycolysis alone. For that reason, fermentation is utilized when oxygen is available; however in the presence of abundant oxygen, some strains of yeast such as Saccharomyces cerevisiae prefer fermentation to aerobic respiration as long as there is an adequate supply of sugars. Some fermentation processes involve obligate anaerobes. Although yeast carries out the fermentation in the production of ethanol in beers and other alcoholic drinks, this is not the only possible agent: bacteria carry out the fermentation in the production of xanthan gum. In ethanol fermentation, one glucose molecule is converted into two ethanol molecules and two carbon dioxide molecules, it is used to make bread dough rise: the carbon dioxide forms bubbles, expanding the dough into a foam. The ethanol is the intoxicating agent in alcoholic beverages such as wine and liquor.
Fermentation of feedstocks, including sugarcane and sugar beets, produces ethanol, added to gasoline. In some species of fish, including goldfish and carp, it provides energy; the figure illustrates the process. Before fermentation, a glucose molecule breaks down into two pyruvate molecules; the energy from this exothermic reaction is used to bind inorganic phosphates to ATP and convert NAD+ to NADH. The pyruvates break down into two acetaldehyde molecules and give off two carbon dioxide molecules as a waste product; the acetaldehyde is reduced into ethanol using the energy and hydrogen from NADH, the NADH is oxidized into NAD+ so that the cycle may repeat. The reaction is catalysed by the enzymes pyruvate alcohol dehydrogenase. Homolactic fermentation is the simplest type of fermentation; the pyruvate from glycolysis undergoes a simple redox reaction. It is unique because it is one of the only respiration processes to not produce a gas as a byproduct. Overall, one molecule of glucose is converted to two molecules of lactic ac