1.
Chemistry
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Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter. Chemistry is sometimes called the science because it bridges other natural sciences, including physics. For the differences between chemistry and physics see comparison of chemistry and physics, the history of chemistry can be traced to alchemy, which had been practiced for several millennia in various parts of the world. The word chemistry comes from alchemy, which referred to a set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism. An alchemist was called a chemist in popular speech, and later the suffix -ry was added to this to describe the art of the chemist as chemistry, the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία and this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, which is in turn derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian. Alternately, al-kīmīā may derive from χημεία, meaning cast together, in retrospect, the definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term chymistry, in the view of noted scientist Robert Boyle in 1661, in 1837, Jean-Baptiste Dumas considered the word chemistry to refer to the science concerned with the laws and effects of molecular forces. More recently, in 1998, Professor Raymond Chang broadened the definition of chemistry to mean the study of matter, early civilizations, such as the Egyptians Babylonians, Indians amassed practical knowledge concerning the arts of metallurgy, pottery and dyes, but didnt develop a systematic theory. Greek atomism dates back to 440 BC, arising in works by such as Democritus and Epicurus. In 50 BC, the Roman philosopher Lucretius expanded upon the theory in his book De rerum natura, unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments. Work, particularly the development of distillation, continued in the early Byzantine period with the most famous practitioner being the 4th century Greek-Egyptian Zosimos of Panopolis. He formulated Boyles law, rejected the four elements and proposed a mechanistic alternative of atoms. Before his work, though, many important discoveries had been made, the Scottish chemist Joseph Black and the Dutchman J. B. English scientist John Dalton proposed the theory of atoms, that all substances are composed of indivisible atoms of matter. Davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current, british William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. The inert gases, later called the noble gases were discovered by William Ramsay in collaboration with Lord Rayleigh at the end of the century, thereby filling in the basic structure of the table. Organic chemistry was developed by Justus von Liebig and others, following Friedrich Wöhlers synthesis of urea which proved that organisms were, in theory
2.
Electron
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The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον
3.
Heterolysis (chemistry)
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In chemistry, heterolysis or heterolytic fission is the process of cleaving a covalent bond where one previously bonded species takes both original bonding electrons from the other species. During heterolytic bond cleavage of a molecule, a cation. Most commonly the more electronegative atom keeps the pair of electrons becoming anionic while the more electropositive atom becomes cationic, heterolytic fission almost always happens to single bonds, the process usually produces 2 fragment species. This became the model for a covalent bond, in 1932 Linus Pauling first proposed the concept of electronegativity, which also introduced the idea that electrons in a covalent bond may not be shared evenly between the bonded atoms. The rate of reaction for many reactions involving unimolecular heterolysis depends heavily on rate of ionization of the covalent bond, the limiting reaction step is generally the formation of ion pairs. One group in the Ukraine did a study on the role of nucleophilic solvation. They found that the rate of heterolysis depends strongly on the nature of the solvent, a change of reaction medium from hexane to water increases the rate of t-BuCl heterolysis by 14 orders of magnitude. This is caused by very strong solvation of the transition state, the main factors that affect heterolysis rates are mainly the solvent’s polarity and electrophilic as well as its ionizing power. The polarizability, nucleophilicity and cohesion of the solvent had a weaker effect on heterolysis. IUPAC, Compendium of Chemical Terminology, 2nd ed. Online corrected version, blanksby, S. J. Ellison, G. B. Bond Dissociation Energies of Organic Molecules, journal of the American Chemical Society. The Nature of the Chemical Bond, the Energy of Single Bonds and the Relative Electronegativity of Atoms. Journal of the American Chemical Society, dvorko, G. F. Ponomareva, E. A. and Ponomarev, M. E. Role of nucleophilic solvation and the mechanism of covalent bond heterolysis. Abraham MH, Doherty RM, Kamlet JM, Harris JM, armentrout, P. B. and Jack Simons
4.
Ion
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An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by chemical or physical means. In chemical terms, if an atom loses one or more electrons. If an atom gains electrons, it has a net charge and is known as an anion. Ions consisting of only a single atom are atomic or monatomic ions, because of their electric charges, cations and anions attract each other and readily form ionic compounds, such as salts. In the case of ionization of a medium, such as a gas, which are known as ion pairs are created by ion impact, and each pair consists of a free electron. The word ion comes from the Greek word ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday also introduced the words anion for a charged ion. In Faradays nomenclature, cations were named because they were attracted to the cathode in a galvanic device, arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions. Arrhenius proposed that ions formed even in the absence of an electric current, ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of charge to give neutral molecules or ionic salts. These stabilized species are commonly found in the environment at low temperatures. A common example is the present in seawater, which are derived from the dissolved salts. Electrons, due to their mass and thus larger space-filling properties as matter waves, determine the size of atoms. Thus, anions are larger than the parent molecule or atom, as the excess electron repel each other, as such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation contains no electrons, and thus consists of a single proton - very much smaller than the parent hydrogen atom. Since the electric charge on a proton is equal in magnitude to the charge on an electron, an anion, from the Greek word ἄνω, meaning up, is an ion with more electrons than protons, giving it a net negative charge. A cation, from the Greek word κατά, meaning down, is an ion with fewer electrons than protons, there are additional names used for ions with multiple charges
5.
Sulfonate
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A sulfonate is a salt or ester of a sulfonic acid. It contains the functional group R-SO3−, anions with the general formula RSO3− are called sulfonates. They are the bases of sulfonic acids with formula RSO2OH. As sulfonic acids tend to be acids, the corresponding sulfonates are weak bases. Due to the stability of sulfonate anions, the cations of sulfonate salts such as scandium triflate have application as Lewis acids, a classic organic reaction for the preparation of sulfonates is that of alkyl halides with sulfites such as sodium sulfite, first described by Adolph Strecker in 1868. The general reaction is, RX + M2SO3 → RSO3M + MX Iodide is used as a catalyst, esters with the general formula R1SO2OR2 are called sulfonic esters. Individual members of the category are named analogously to how ordinary carboxyl esters are named, for example, if the R2 group is a methyl group and the R1 group is a trifluoromethyl group, the resulting compound is methyl trifluoromethanesulfonate. Sulfonic esters are used as reagents in organic synthesis, chiefly because the RSO3− group is a leaving group. Methyl triflate, for example, is a methylating reagent. Sulfonates are commonly used to confer water solubility to protein crosslinkers such as N-hydroxysulfosuccinimide, BS3, Sulfo-SMCC, cyclic sulfonic esters are called sultones. Some sultones are short-lived intermediates, used as alkylating agents to introduce a negatively charged sulfonate group. In the presence of water, they hydrolyze to the hydroxy sulfonic acids. Sultone oximes are key intermediates in the synthesis of the anti-convulsant drug zonisamide, tisocromide is an example of a sultone. Mesylate, CH3SO3− Triflate, CF3SO3− Ethanesulfonate, C2H5SO3− Tosylate, CH3C6H4SO3− Benzenesulfonic acid, C6H5SO3− Closilate, ClC6H4SO3− Camphorsulfonate, SO3− Sulfate Sulfoxide Sulfonyl
6.
Tosyl
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This group is usually derived from the compound tosyl chloride, CH3C6H4SO2Cl, which forms esters and amides of toluenesulfonic acid. The para orientation illustrated is most common, and by convention tosyl refers to the p-toluenesulfonyl group, tosylate refers to the anion of p-toluenesulfonic acid and it is abbreviated as TsO−, or it may refer to esters of p-toluenesulfonic acid. For SN2 reactions, alkyl alcohols can also be converted to alkyl tosylates, in this reaction, the lone pair of the alcohol oxygen attacks the sulfur of the tosyl chloride, kicking off the chloride group and forming the tosylate with retention of reactant stereochemistry. This is useful because alcohols are poor leaving groups in SN2 reactions and it is the transformation of alkyl alcohols to alkyl tosylates that allows an SN2 reaction to occur in the presence of a good nucleophile. A tosyl group can function as a group in organic synthesis. Alcohols can be converted to groups so that they do not react. The tosylate group may later be converted back into an alcohol, the latter is a leaving group for displacement by diisopropylamine, The tosyl group is also useful as a protecting group for amines. The resulting sulfonamide structure is extremely stable and it can be deprotected to reveal the amine using reductive or strongly acidic conditions. Tosyl group is used as a protecting group for amines in organic synthesis. Tosyl chloride and pyridine in dichloromethane HBr and acetic acid at 70 °C Refluxing with TMSCl, sodium iodide, there are p-nitrobenzenesulfonates and p-bromobenzenesulfonates, respectively
7.
Sarin
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Sarin, or GB, is a colorless, odorless liquid, used as a chemical weapon owing to its extreme potency as a nerve agent. It is generally considered a weapon of mass destruction, production and stockpiling of sarin was outlawed as of April 1997 by the Chemical Weapons Convention of 1993, and it is classified as a Schedule 1 substance. In June 1994, the UN Special Commission on Iraqi disarmament destroyed the nerve agent sarin under Security Council resolution 687 concerning the disposal of Iraqs weapons of mass destruction, Sarin is an organophosphorus compound with the formula CH3PF. People who absorb a non-lethal dose, but do not receive medical treatment. Sarin is a molecule because it has four chemically distinct substituents attached to the tetrahedral phosphorus center. The SP form is the active enantiomer due to its greater binding affinity to acetylcholinesterase. The P-F bond is broken by nucleophilic agents, such as water. At high pH, sarin decomposes rapidly to nontoxic phosphonic acid derivatives and it is usually manufactured and weaponized as a racemic mixture—an equal mixture of both enantiomeric forms, as this is a simpler process and provides an adequate weapon. A number of pathways can be used to create sarin. The final reaction typically involves attachment of the group to the phosphorus with an alcoholysis with isopropyl alcohol. Two variants of this process are common and this reaction also gives sarin, but hydrochloric acid as a byproduct instead. The Di-Di process was used by the United States for the production of its unitary sarin stockpile, the scheme below describes an example of Di-Di process. The selection of reagents is arbitrary and reaction conditions and product yield depend on the selected reagents, inert atmosphere and anhydrous conditions are used for synthesis of sarin and other organophosphates. As both reactions leave considerable acid in the product, bulk sarin produced without further treatment has a poor shelf life. Various methods have been tried to resolve these problems, triethylamine was added to UK sarin, with relatively poor success. The Aum Shinrikyo cult experimented with triethylamine as well, N, N-Diethylaniline was used by Aum Shinrikyo for acid reduction. N, N′-Diisopropylcarbodimide was added to sarin produced at Rocky Mountain Arsenal to combat corrosion, isopropylamine was included as part of the M687 155mm field artillery shell, which was a binary sarin weapon system developed by the US Army. Another byproduct of these two processes is diisopropyl methylphosphonate, formed when a second isopropyl alcohol reacts with the sarin itself
8.
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
9.
Nitration
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Nitration is a general class of chemical process for the introduction of a nitro group into an organic chemical compound. More loosely the term also is applied incorrectly to the different process of forming nitrate esters between alcohols and nitric acid, as occurs in the synthesis of nitroglycerin. There are many industrial applications of nitration in the strict sense. Nitration reactions are used for the production of explosives, for example the conversion of guanidine to nitroguanidine. However, they are of importance as chemical intermediates and precursors. Millions of tons of nitroaromatics are produced annually, typical nitration syntheses apply so-called mixed acid, a mixture of concentrated nitric acid and sulfuric acids. This mixture produces the nitronium ion, which is the species in aromatic nitration. This active ingredient, which can be isolated in the case of nitronium tetrafluoroborate, in mixed-acid syntheses sulfuric acid is not consumed and hence acts as a catalyst as well as an absorbent for water. In the case of nitration of benzene, the reaction is conducted at 50 °C, selectivity can be a challenge in nitrations because as a rule more than one compound may result but only one is desired, so alternative products act as contaminants or are simply wasted. Accordingly, it is desirable to design syntheses with suitable selectivity, for example, by controlling the reaction conditions, the substituents on aromatic rings affect the rate of this electrophilic aromatic substitution. Deactivating groups such as nitro groups have an electron-withdrawing effect. Such groups deactivate the reaction and directs the electrophilic nitronium ion to attack the aromatic meta position, deactivating meta-directing substituents include sulfonyl, cyano groups, keto, esters, and carboxylates. Nitration can be accelerated by activating groups such as amino, hydroxy and methyl groups also amides and ethers resulting in para, the direct nitration of aniline with nitric acid and sulfuric acid, according to one source results in a 50/50 mixture of para and meta nitroaniline. In this reaction the fast-reacting and activating aniline exists in equilibrium with the abundant but less reactive anilinium ion. According to another source a more controlled nitration of aniline starts with the formation of acetanilide by reaction with acetic anhydride followed by the actual nitration, because the amide is a regular activating group the products formed are the para and ortho isomers. Heating the reaction mixture is sufficient to hydrolyze the amide back to the nitrated aniline, in the Wolfenstein-Boters reaction, benzene reacts with nitric acid and mercury nitrate to give picric acid
10.
Benzene
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Benzene is an important organic chemical compound with the chemical formula C6H6. The benzene molecule is composed of 6 carbon atoms joined in a ring with 1 hydrogen atom attached to each, because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a constituent of crude oil and is one of the elementary petrochemicals. Because of the cyclic continuous pi bond between the atoms, benzene is classed as an aromatic hydrocarbon, the second -annulene. Benzene is a colorless and highly flammable liquid with a sweet smell and it is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced. Because benzene has a high number, it is an important component of gasoline. Because benzene is a carcinogen, most non-industrial applications have been limited. The word benzene derives historically from gum benzoin, a resin known to European pharmacists. An acidic material was derived from benzoin by sublimation, and named flowers of benzoin, the hydrocarbon derived from benzoic acid thus acquired the name benzin, benzol, or benzene. Michael Faraday first isolated and identified benzene in 1825 from the oily residue derived from the production of illuminating gas, in 1833, Eilhard Mitscherlich produced it by distilling benzoic acid and lime. He gave the compound the name benzin, in 1845, Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar. Four years later, Mansfield began the first industrial-scale production of benzene, gradually, the sense developed among chemists that a number of substances were chemically related to benzene, comprising a diverse chemical family. In 1855, Hofmann used the word aromatic to designate this family relationship, in 1997, benzene was detected in deep space. The empirical formula for benzene was known, but its highly polyunsaturated structure. In 1865, the German chemist Friedrich August Kekulé published a paper in French suggesting that the structure contained a ring of six carbon atoms with alternating single and double bonds, the next year he published a much longer paper in German on the same subject. Kekulés symmetrical ring could explain these facts, as well as benzenes 1,1 carbon-hydrogen ratio. Here Kekulé spoke of the creation of the theory and he said that he had discovered the ring shape of the benzene molecule after having a reverie or day-dream of a snake seizing its own tail. This vision, he said, came to him years of studying the nature of carbon-carbon bonds
11.
Transition state theory
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Transition state theory explains the reaction rates of elementary chemical reactions. The theory assumes a special type of equilibrium between reactants and activated transition state complexes. TST is used primarily to understand qualitatively how chemical reactions take place and this theory was developed simultaneously in 1935 by Henry Eyring, then at Princeton University, and by Meredith Gwynne Evans and Michael Polanyi of the University of Manchester. TST is also referred to as theory, absolute-rate theory. Before the development of TST, the Arrhenius rate law was used to determine energies for the reaction barrier. Therefore, further development was necessary to understand the two associated with this law, the pre-exponential factor and the activation energy. During that period, many scientists and researchers contributed significantly to the development of the theory, the basic ideas behind transition state theory are as follows, Rates of reaction can be studied by examining activated complexes near the saddle point of a potential energy surface. The details of how these complexes are formed are not important, the saddle point itself is called the transition state. The activated complexes are in an equilibrium with the reactant molecules. The activated complexes can convert into products, and kinetic theory can be used to calculate the rate of this conversion, by the early 20th century many had accepted the Arrhenius equation, but the physical interpretation of A and Ea remained vague. In 1910, French chemist René Marcelin introduced the concept of standard Gibbs energy of activation and they proposed the following rate constant equation k ∝ exp exp However, the nature of the constant was still unclear. In early 1900, Max Trautz and William Lewis studied the rate of the reaction using collision theory, Lewis applied his treatment to the following reaction and obtained good agreement with experimental result. 2HI → H2 + I2 However, later when the treatment was applied to other reactions. Statistical mechanics played a significant role in the development of TST and it was not until 1912 when the French chemist A. Berthoud used the Maxwell–Boltzmann distribution law to obtain an expression for the rate constant. D ln k d T = a − b T R T2 where a and b are constants related to energy terms. Two years later, René Marcelin made a contribution by treating the progress of a chemical reaction as a motion of a point in phase space. He then applied Gibbs statistical-mechanical procedures and obtained a similar to the one he had obtained earlier from thermodynamic consideration. In 1915, another important contribution came from British physicist James Rice, based on his statistical analysis, he concluded that the rate constant is proportional to the critical increment
12.
Acid dissociation constant
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An acid dissociation constant, Ka, is a quantitative measure of the strength of an acid in solution. It is the constant for a chemical reaction known as dissociation in the context of acid–base reactions. In the example shown in the figure, HA represents acetic acid, and A− represents the acetate ion, the chemical species HA, A− and H3O+ are said to be in equilibrium when their concentrations do not change with the passing of time. The definition can then be more simply H A ⇌ A − + H +, K a = This is the definition in common usage. A weak acid has a pKa value in the approximate range −2 to 12 in water, pKa values for strong acids can, however, be estimated by theoretical means. The definition can be extended to non-aqueous solvents, such as acetonitrile and dimethylsulfoxide. Denoting a solvent molecule by S H A + S ⇌ A − + S H +, K a = When the concentration of solvent molecules can be taken to be constant, K a =, as before. The value of pKa also depends on structure of the acid in many ways. For example, Pauling proposed two rules, one for successive pKa of polyprotic acids, and one to estimate the pKa of oxyacids based on the number of =O and −OH groups. Other structural factors that influence the magnitude of the dissociation constant include inductive effects, mesomeric effects. Hammett type equations have frequently applied to the estimation of pKa. The quantitative behaviour of acids and bases in solution can be only if their pKa values are known. These calculations find application in different areas of chemistry, biology, medicine. Acid dissociation constants are essential in aquatic chemistry and chemical oceanography. In living organisms, acid–base homeostasis and enzyme kinetics are dependent on the pKa values of the acids and bases present in the cell. According to Arrheniuss original definition, an acid is a substance that dissociates in solution, releasing the hydrogen ion H+. The equilibrium constant for this reaction is known as a dissociation constant. Brønsted and Lowry generalised this further to an exchange reaction
13.
Conjugate acid
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A conjugate acid, within the Brønsted–Lowry acid–base theory, is a species formed by the reception of a proton by a base—in other words, it is a base with a hydrogen ion added to it. On the other hand, a base is merely what is left after an acid has donated a proton in a chemical reaction. Hence, a base is a species formed by the removal of a proton from an acid. A proton is a particle with a unit positive electrical charge, it is represented by the symbol H+ because it constitutes the nucleus of a hydrogen atom, that is. A cation can be an acid, and an anion can be a conjugate base, depending on which substance is involved. In an acid-base reaction, an acid plus a base reacts to form a conjugate base plus a conjugate acid, refer to the following figure, We say that the water molecule is the conjugate acid of the hydroxide ion after the latter received the hydrogen proton donated by ammonium. On the other hand, ammonia is the base for the acid ammonium after ammonium has donated a hydrogen ion towards the production of the water molecule. The strength of an acid is directly proportional to its dissociation constant. If a conjugate acid is strong, its dissociation will have an equilibrium constant. The strength of a base can be seen as the tendency of the species to pull hydrogen protons towards itself. If a conjugate base is classified as strong, it will hold on to the hydrogen proton when in solution, if a chemical species is classified as a weak acid, its conjugate base will be strong in nature. This can be observed in ammonias reaction with water, the reaction proceeds until most of the ammonia has been transformed to ammonium. This shift to the right in the equilibrium of the reaction means that ammonium does not dissociate easily in water. On the other hand, if a species is classified as a strong acid, an example of this case would be the dissociation of Hydrochloric acid HCl in water. Since HCl is an acid, its conjugate base will be a weak conjugate base. Therefore, in system, most H+ will be in the form of a Hydronium ion H 3O+ instead of attached to a Cl anion. To summarize, the stronger the acid or base, the weaker the conjugate, the acid and conjugate base as well as the base and conjugate acid are known as conjugate pairs. When finding a conjugate acid or base, it is important to look at the reactants of the chemical equation, to identify the conjugate acid, look for the pair of compounds that are related
14.
Nitrogen
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Nitrogen is a chemical element with symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772, although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. Nitrogen is the lightest member of group 15 of the periodic table, the name comes from the Greek πνίγειν to choke, directly referencing nitrogens asphyxiating properties. It is an element in the universe, estimated at about seventh in total abundance in the Milky Way. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless diatomic gas with the formula N2, dinitrogen forms about 78% of Earths atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids, in the nucleic acids, the human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, many industrially important compounds, such as ammonia, nitric acid, organic nitrates, and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen, the second strongest bond in any diatomic molecule. Synthetically produced ammonia and nitrates are key industrial fertilisers, and fertiliser nitrates are key pollutants in the eutrophication of water systems. Apart from its use in fertilisers and energy-stores, nitrogen is a constituent of organic compounds as diverse as Kevlar used in high-strength fabric, Nitrogen is a constituent of every major pharmacological drug class, including antibiotics. Many notable nitrogen-containing drugs, such as the caffeine and morphine or the synthetic amphetamines. Nitrogen compounds have a long history, ammonium chloride having been known to Herodotus. They were well known by the Middle Ages, alchemists knew nitric acid as aqua fortis, as well as other nitrogen compounds such as ammonium salts and nitrate salts. The mixture of nitric and hydrochloric acids was known as aqua regia, celebrated for its ability to dissolve gold, the discovery of nitrogen is attributed to the Scottish physician Daniel Rutherford in 1772, who called it noxious air. Though he did not recognise it as a different chemical substance, he clearly distinguished it from Joseph Blacks fixed air. The fact that there was a component of air that does not support combustion was clear to Rutherford, Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as burnt air or phlogisticated air. Nitrogen gas was inert enough that Antoine Lavoisier referred to it as air or azote, from the Greek word άζωτικός. In an atmosphere of nitrogen, animals died and flames were extinguished
15.
Ether
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Ethers are a class of organic compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula R–O–R′, where R and R′ represent the alkyl or aryl groups, a typical example of the first group is the solvent and anesthetic diethyl ether, commonly referred to simply as ether. Ethers are common in chemistry and pervasive in biochemistry, as they are common linkages in carbohydrates. Ethers feature C–O–C linkage defined by an angle of about 110°. The barrier to rotation about the C–O bonds is low, the bonding of oxygen in ethers, alcohols, and water is similar. In the language of valence bond theory, the hybridization at oxygen is sp3, oxygen is more electronegative than carbon, thus the hydrogens alpha to ethers are more acidic than in simple hydrocarbons. They are far less acidic than hydrogens alpha to carbonyl groups, depending on the groups at R and R′, ethers are classified into two types, Simple ethers or symmetrical ethers, e. g. diethyl ether, dimethyl ether, etc. Mixed ethers or unsymmetrical ethers, e. g. methyl ethyl ether, methyl phenyl ether, in the IUPAC nomenclature system, ethers are named using the general formula alkoxyalkane, for example CH3–CH2–O–CH3 is methoxyethane. If the ether is part of a complex molecule, it is described as an alkoxy substituent. The simpler alkyl radical is written in front, so CH3–O–CH2CH3 would be given as methoxyethane, IUPAC rules are often not followed for simple ethers. The trivial names for simple ethers are a composite of the two followed by ether. For example, ethyl ether, diphenylether. As for other compounds, very common ethers acquired names before rules for nomenclature were formalized. Diethyl ether is called ether, but was once called sweet oil of vitriol. Methyl phenyl ether is anisole, because it was found in aniseed. Acetals are another class of ethers with characteristic properties, polyethers are compounds with more than one ether group. The crown ethers are examples of small polyethers, some toxins produced by dinoflagellates such as brevetoxin and ciguatoxin are extremely large and are known as cyclic or ladder polyethers. Polyether generally refers to polymers which contain the functional group in their main chain
16.
Triflate
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Trifluoromethanesulfonate, also known by the trivial name triflate, is a functional group with the formula CF3SO3−. The triflate group is represented by −OTf, as opposed to −Tf. For example, n-butyl triflate can be written as CH3CH2CH2CH2OTf, the corresponding triflate anion, CF 3SO−3, is an extremely stable polyatomic ion, being the conjugate base of triflic acid, one of the strongest acids known. It is defined as a superacid, because it is more acidic than sulfuric acid. A triflate group is an excellent leaving group used in organic reactions such as nucleophilic substitution, Suzuki couplings. Since alkyl triflates are extremely reactive in SN2 reactions, they must be stored in free of nucleophiles. The anion owes its stability to resonance stabilization which causes the charge to be spread over the three oxygen atoms and the sulfur atom. An additional stabilization is achieved by the group as a strong electron-withdrawing group. Triflates have also applied as ligands for group 11 and 13 metals along with lanthanides. Lithium triflates are used in lithium ion batteries as a component of the electrolyte. A mild triflating reagent is phenyl triflimide or N, N-bisaniline, Triflate salts are thermally very stable with melting points up to 350 °C for sodium, boron and silver salts especially in water-free form. They can be obtained directly from triflic acid and the hydroxide or metal carbonate in water. Especially useful are the lanthanide triflates of the type Ln3, a related popular catalyst scandium triflate is used in such reactions as aldol reactions and Diels-Alder reactions. An example is the Mukaiyama aldol addition reaction between benzaldehyde and the enol ether of cyclohexanone with an 81% chemical yield. The corresponding reaction with the yttrium salt fails, Triflate is a commonly used counterion for organometallic complexes, methyl triflate Nonaflate Trifluoromethanesulfonic acid Metal triflimidate Comins reagent
17.
Tosylate
–
This group is usually derived from the compound tosyl chloride, CH3C6H4SO2Cl, which forms esters and amides of toluenesulfonic acid. The para orientation illustrated is most common, and by convention tosyl refers to the p-toluenesulfonyl group, tosylate refers to the anion of p-toluenesulfonic acid and it is abbreviated as TsO−, or it may refer to esters of p-toluenesulfonic acid. For SN2 reactions, alkyl alcohols can also be converted to alkyl tosylates, in this reaction, the lone pair of the alcohol oxygen attacks the sulfur of the tosyl chloride, kicking off the chloride group and forming the tosylate with retention of reactant stereochemistry. This is useful because alcohols are poor leaving groups in SN2 reactions and it is the transformation of alkyl alcohols to alkyl tosylates that allows an SN2 reaction to occur in the presence of a good nucleophile. A tosyl group can function as a group in organic synthesis. Alcohols can be converted to groups so that they do not react. The tosylate group may later be converted back into an alcohol, the latter is a leaving group for displacement by diisopropylamine, The tosyl group is also useful as a protecting group for amines. The resulting sulfonamide structure is extremely stable and it can be deprotected to reveal the amine using reductive or strongly acidic conditions. Tosyl group is used as a protecting group for amines in organic synthesis. Tosyl chloride and pyridine in dichloromethane HBr and acetic acid at 70 °C Refluxing with TMSCl, sodium iodide, there are p-nitrobenzenesulfonates and p-bromobenzenesulfonates, respectively
18.
Mesylate
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In chemistry, a mesylate is any salt or ester of methanesulfonic acid. In salts, the mesylate is present as the CH3SO3− anion, when modifying the International Nonproprietary Name of a pharmaceutical substance containing the group or anion, the correct spelling is mesilate. Mesylate esters are a group of compounds that share a common functional group with the general structure CH3SO2O–R, abbreviated MsO–R. Mesylate is considered a group in nucleophilic substitution reactions. Mesylates are generally prepared by treating an alcohol and methanesulfonyl chloride in the presence of a base, related to mesylate, is the mesyl, an abbreviation for methanesulfonyl or CH3SO2 functional group. For example, methanesulfonyl chloride is often referred to as mesyl chloride, whereas mesylates are often hydrolytically labile, mesyl groups, when attached to nitrogen are robust with respect to hydrolysis. This functional group appears in a variety of medications, particularly cardiac, examples include Sotalol, ibutilide, sematilide, Dronedarone, Dofetilide, E-4031, and Bitopertin. Ice core samples from a spot in Antarctica were found to have tiny inclusions of magnesium methanesulfonate dodecahydrate. This natural phase is recognized as the mineral ernstburkeite
19.
Alcohol
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In chemistry, an alcohol is any organic compound in which the hydroxyl functional group is bound to a saturated carbon atom. The term alcohol originally referred to the alcohol ethanol, the predominant alcohol in alcoholic beverages. The suffix -ol in non-systematic names also typically indicates that the substance includes a functional group and, so. But many substances, particularly sugars contain hydroxyl functional groups without using the suffix, an important class of alcohols, of which methanol and ethanol are the simplest members is the saturated straight chain alcohols, the general formula for which is CnH2n+1OH. The word alcohol is from the Arabic kohl, a used as an eyeliner. Al- is the Arabic definite article, equivalent to the in English, alcohol was originally used for the very fine powder produced by the sublimation of the natural mineral stibnite to form antimony trisulfide Sb 2S3, hence the essence or spirit of this substance. It was used as an antiseptic, eyeliner, and cosmetic, the meaning of alcohol was extended to distilled substances in general, and then narrowed to ethanol, when spirits as a synonym for hard liquor. Bartholomew Traheron, in his 1543 translation of John of Vigo, Vigo wrote, the barbarous auctours use alcohol, or alcofoll, for moost fine poudre. The 1657 Lexicon Chymicum, by William Johnson glosses the word as antimonium sive stibium, by extension, the word came to refer to any fluid obtained by distillation, including alcohol of wine, the distilled essence of wine. Libavius in Alchymia refers to vini alcohol vel vinum alcalisatum, Johnson glosses alcohol vini as quando omnis superfluitas vini a vino separatur, ita ut accensum ardeat donec totum consumatur, nihilque fæcum aut phlegmatis in fundo remaneat. The words meaning became restricted to spirit of wine in the 18th century and was extended to the class of substances so-called as alcohols in modern chemistry after 1850, the term ethanol was invented 1892, based on combining the word ethane with ol the last part of alcohol. In the IUPAC system, in naming simple alcohols, the name of the alkane chain loses the terminal e and adds ol, e. g. as in methanol and ethanol. When necessary, the position of the group is indicated by a number between the alkane name and the ol, propan-1-ol for CH 3CH 2CH 2OH, propan-2-ol for CH 3CHCH3. If a higher priority group is present, then the prefix hydroxy is used, in other less formal contexts, an alcohol is often called with the name of the corresponding alkyl group followed by the word alcohol, e. g. methyl alcohol, ethyl alcohol. Propyl alcohol may be n-propyl alcohol or isopropyl alcohol, depending on whether the group is bonded to the end or middle carbon on the straight propane chain. As described under systematic naming, if another group on the molecule takes priority, Alcohols are then classified into primary, secondary, and tertiary, based upon the number of carbon atoms connected to the carbon atom that bears the hydroxyl functional group. The primary alcohols have general formulas RCH2OH, the simplest primary alcohol is methanol, for which R=H, and the next is ethanol, for which R=CH3, the methyl group. Secondary alcohols are those of the form RRCHOH, the simplest of which is 2-propanol, for the tertiary alcohols the general form is RRRCOH
20.
Chloride
–
The chloride ion /ˈklɔəraɪd/ is the anion Cl−. It is formed when the element chlorine gains an electron or when a compound such as chloride is dissolved in water or other polar solvents. Chloride salts such as sodium chloride are often soluble in water. It is an essential electrolyte located in all body fluids responsible for maintaining acid/base balance, transmitting nerve impulses and regulating fluid in, less frequently, the word chloride may also form part of the common name of chemical compounds in which one or more chlorine atoms are covalently bonded. For example, methyl chloride, with the standard name chloromethane is a compound with a covalent C−Cl bond in which the chlorine is not an anion. A chloride ion is much larger than an atom,167 and 99 pm. The ion is colorless and diamagnetic, in aqueous solution, it is highly soluble in most cases, however, some chloride salts, such as silver chloride, lead chloride, and mercury chloride are slightly soluble in water. In aqueous solution, chloride is bound by the end of the water molecules. Some chloride-containing minerals include the chlorides of sodium, potassium, and magnesium, called serum chloride, the concentration of chloride in the blood is regulated by the kidneys. A chloride ion is a component of some proteins, e. g. it is present in the amylase enzyme. The chlor-alkali industry is a consumer of the worlds energy budget. This process converts sodium chloride into chlorine and sodium hydroxide, which are used to make many other materials and chemicals, in the petroleum industry, the chlorides are a closely monitored constituent of the mud system. An increase of the chlorides in the mud system may be an indication of drilling into a high-pressure saltwater formation and its increase can also indicate the poor quality of a target sand. Chloride is also a useful and reliable chemical indicator of river / groundwater fecal contamination, as chloride is a non-reactive solute, many water regulating companies around the world utilize chloride to check the contamination levels of the rivers and potable water sources. Chloride salts such as sodium chloride are used to preserve food, chloride is an essential electrolyte, trafficking in and out of cells through chloride channels and playing a key role in maintaining cell homeostasis and transmitting action potentials in neurons. Characteristic concentrations of chloride in model organisms are, in both E. coli and budding yeast are 10-200mM, in mammalian cell 5-100mM and in blood plasma 100mM, chloride can be oxidized but not reduced. The first oxidation, as employed in the process, is conversion to chlorine gas. Chlorine can be oxidized to other oxides and oxyanions including hypochlorite, chlorine dioxide, chlorate
