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Geminal Diol
A geminal diol (or gem-diol for short) is any organic compound having two hydroxyl functional groups () bound to the same carbon atom. Geminal diols are a subclass of the diols, which in turn are a special class of alcohols. Most of the geminal diols are considered unstable. The simplest geminal diol is methanediol or . Other examples are: * dihydroxymalinic acid * decahydroxycyclopentane *chloral hydrate Reactions Hydration equilibrium Geminal diols can be viewed as ketone (or aldehyde) hydrates. The two hydroxyl groups in a geminal diol are easily converted to a carbonyl or keto group C=O by loss of one water molecule. Conversely, a keto group can combine with water to form the geminal hydroxyl groups. The equilibrium in water solution may be shifted towards either compound. For example, the equilibrium constant for the conversion of acetone to propane-2,2-diol is about 10−3, while that of formaldehyde to methanediol is 103.Eric V. Anslyn, Dennis A. Dougherty ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equilibrium Constant
The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency towards further change. For a given set of reaction conditions, the equilibrium constant is independent of the initial analytical concentrations of the reactant and product species in the mixture. Thus, given the initial composition of a system, known equilibrium constant values can be used to determine the Chemical equilibrium#Composition of a mixture, composition of the system at equilibrium. However, reaction parameters like temperature, solvent, and ionic strength may all influence the value of the equilibrium constant. A knowledge of equilibrium constants is essential for the understanding of many chemical systems, as well as the biochemical processes such as oxygen transport by hemoglobin in blood and acid–base homeostasis in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geminal
In chemistry, the descriptor geminal () refers to the relationship between two atoms or functional groups that are attached to the same atom. A geminal diol, for example, is a diol (a molecule that has two alcohol functional groups) attached to the same carbon atom, as in methanediol. Also the shortened prefix ''gem'' may be applied to a chemical name to denote this relationship, as in a ''gem''-dibromide for "geminal dibromide". The concept is important in many branches of chemistry, including synthesis and spectroscopy, because functional groups attached to the same atom often behave differently from when they are separated. Geminal diols, for example, are easily converted to ketones or aldehydes with loss of water.Peter Taylor (2002)''Mechanism and synthesis'' Book 10 of ''Molecular world''. Open University, Royal Society of Chemistry; . 368 pages The related term '' vicinal'' refers to the relationship between two functional groups that are attached to adjacent atoms. Thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemiacetal
In organic chemistry, a hemiacetal is a functional group the general formula , where is a hydrogen atom or an organic substituent. They generally result from the nucleophilic Addition reaction, addition of an Alcohol (chemistry), alcohol (a compound with at least one hydroxy group) to an aldehyde () or a ketone () under acidic conditions. The addition of an alcohol to a ketone is more commonly referred to as a hemiketal. Common examples of hemiacetals include cyclic Monosaccharide, monosaccharides. Hemiacetals have use as a protecting group and in synthesizing oxygenated heterocycles like Tetrahydrofuran, tetrahydrofurans. Nomenclature According to the IUPAC definition of a hemiacetal, the R1 and R2 groups may or may not be hydrogen. In a hemiketal, both of these R-groups must not be hydrogen. Thus, hemiketals are regarded as a subclass of hemiacetals. The prefix ''hemi,'' meaning half, refers to the one alcohol added to the carbonyl group. This is half of the required alcohols to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dodecahydroxycyclohexane
Dodecahydroxycyclohexane is an organic compound with molecular formula or or . It is a sixfold geminal diol with a cyclohexane backbone and can be regarded as a sixfold hydrate of cyclohexanehexone (). Dihydrate The dihydrate can be crystallized from methanol as colorless plates or prisms, that decomposes at about 100 °C. This compound was synthesized by Joseph Udo Lerch (1816–1892) in 1862 by oxidation of benzenehexol or tetrahydroxy-''p''-benzoquinone and characterized by Rudolf Nietzki and in 1885, although the product was for a long time assumed to be hexaketocyclohexane with water of crystallization (). Indeed, this product is still commonly marketed as cyclohexanehexone octahydrate, hexaketocyclohexane octahydrate, triquinoyl octahydrate and similar names. Its true nature was suspected since the 1950s or earlier, but was confirmed by X-ray diffraction X-ray diffraction is a generic term for phenomena associated with changes in the direction of X-ray beams ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trichloromethyl Group
The trichloromethyl group is a functional group that has the chemical formula, formula . The naming of is group is derived from the methyl group (which has the formula ), by replacing each hydrogen atom by a chlorine atom. Compounds with this group are a subclass of the organochlorines. Some notable examples of compounds with this group are trichloromethane , 1,1,1-trichloroethane , and chloral . The trichloromethyl group has a significant electronegativity. For this reason, trichloromethyl-substituted acids, such as trichloromethanesulfonic acid, are often stronger than the original. For example, the acidity constant (pKa) of trichloroacetic acid – is 0.77, whereas that of acetic acid is 4.76. By the same principle, the trichloromethyl group generally lowers the basicity of organic compounds, e.g. trichloroethanol. See also * Trifluoromethyl group * Trichloromethoxy References [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chloral
Chloral, also known as trichloroacetaldehyde or trichloroethanal, is the organic compound with the formula Cl3CCHO. This aldehyde is a colourless liquid that is soluble in a wide range of solvents. It reacts with water to form chloral hydrate, a once widely used sedative and hypnotic substance. Production Chloral was first prepared, and named, by the German chemist Justus von Liebig in 1832. Liebig treated anhydrous ethanol with dry chlorine gas. Chloral is produced commercially by the chlorination of acetaldehyde in the presence of hydrochloric acid, producing chloral hydrate. Ethanol can also be used as a feedstock. This reaction is catalyzed by antimony trichloride: :H3CCHO + 3 Cl2 + H2O → Cl3CCH(OH)2 + 3 HCl The chloral hydrate is distilled from the reaction mixture. The distillate is then dehydrated with concentrated sulfuric acid, after which the heavier acid layer (containing the water) is drawn off: :Cl3CCH(OH)2 → Cl3CCHO + H2O The resulting product is p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trifluoromethyl Group
The trifluoromethyl group is a functional group that has the formula . The naming of is group is derived from the methyl group (which has the formula ), by replacing each hydrogen atom by a fluorine atom. Some common examples are trifluoromethane , 1,1,1-trifluoroethane , and hexafluoroacetone . Compounds with this group are a subclass of the organofluorines. Properties The trifluoromethyl group has a significant electronegativity that is often described as being intermediate between the electronegativities of fluorine and chlorine. For this reason, trifluoromethyl-substituted compounds are often strong acids, such as trifluoromethanesulfonic acid and trifluoroacetic acid. Conversely, the trifluoromethyl group lowers the basicity of compounds like trifluoroethanol. Uses The trifluoromethyl group occurs in certain pharmaceuticals, drugs, and abiotically synthesized natural fluorocarbon based compounds. The medicinal use of the trifloromethyl group dates from 1928, although res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexafluoroacetone
Hexafluoroacetone (HFA) is a chemical compound with the formula (CF3)2CO. It is structurally similar to acetone; however, its reactivity is markedly different. It is a colourless, hygroscopic, nonflammable, highly reactive gas characterized by a musty odour. According to electron diffraction, HFA and acetone adopt very similar structures, the C-O distance being only longer in the fluorinated compound (124.6 vs 121.0 pm), possibly due to steric effects. The term "hexafluoroacetone" can refer to the sesquihydrate (1.5 H2O), which is a hemihydrate of hexafluoropropane-2,2-diol , a geminal diol. Hydrated HFA behaves differently from the anhydrous material. Synthesis The industrial route to HFA involves treatment of hexachloroacetone with HF (a Finkelstein reaction): :(CCl3)2CO + 6 HF → (CF3)2CO + 6 HCl Laboratory methods Hydrated HFA can be converted to HFA by treatment with hot sulfuric acid. It has also be prepared from hexafluoropropylene oxide, which will rearrange ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formaldehyde
Formaldehyde ( , ) (systematic name methanal) is an organic compound with the chemical formula and structure , more precisely . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as aqueous solutions (formalin), which consists mainly of the hydrate CH2(OH)2. It is the simplest of the aldehydes (). As a precursor to many other materials and chemical compounds, in 2006 the global production of formaldehyde was estimated at 12 million tons per year. It is mainly used in the production of industrial resins, e.g., for particle board and coatings. Formaldehyde also occurs naturally. It is derived from the degradation of serine, dimethylglycine, and lipids. Demethylases act by converting N-methyl groups to formaldehyde. Formaldehyde is classified as a group 1 carcinogen and can cause respiratory and skin irritation upon exposure. Forms Formaldehyde is more complicated than many simple carbon compounds in that i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
