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Solketal
Solketal is a protected form of glycerol with an isopropylidene acetal group joining two neighboring hydroxyl groups. Solketal contains a chiral center on the center carbon of the glycerol backbone, and so can be purchased as either the racemate or as one of the two enantiomers. Solketal has been used extensively in the synthesis of mono-, di- and triglycerides by ester bond formation. The free hydroxyl groups of solketal can be esterified In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ... with a carboxylic acid to form the protected monoglyceride, where the isopropylene group can then be removed using an acid catalyst in aqueous or alcoholic medium. The unprotected diol can then be esterified further to form either the di- or triglyceride. References * * * * {{cite journal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycerol
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known as glycerides. Because it has antimicrobial and antiviral properties, it is widely used in wound and burn treatments approved by the U.S. Food and Drug Administration. Conversely, it is also used as a bacterial culture medium. It can be used as an effective marker to measure liver disease. It is also widely used as a sweetener in the food industry and as a humectant in pharmaceutical formulations. Because of its three hydroxyl groups, glycerol is miscible with water and is hygroscopic in nature. Structure Although achiral, glycerol is prochiral with respect to reactions of one of the two primary alcohols. Thus, in substituted derivatives, the stereospecific numbering labels the molecule with a "sn-" prefix before the stem name of the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isopropylidene Acetal
In organic chemistry, an acetonide is the functional group composed of the cyclic ketal of a diol with acetone. The more systematic name for this structure is an isopropylidene ketal. Acetonide is a common protecting group for 1,2- and 1,3-diols. The protecting group can be removed by hydrolysis of the ketal using dilute aqueous acid. Example The acetonides of small di- and triols, as well as many sugars and sugar alcohols, are common. The hexaol mannitol reacts with 2,2-dimethoxypropane to give the bis-acetonide, which oxidizes to give the acetonide of glyceraldehyde: :(CHOHCHOHCH2OH)2 + 2 (MeO)2CMe2 → (CHOHCHCH2O2CMe2)2 + 4 MeOH :(CHOHCHOCH2OCMe2)2 + → 2 OCHCHCH2O2CMe2 + H2O An example of its use as a protecting group in a complex organic synthesis is the Nicolaou Taxol total synthesis. It is a common protecting group for sugars and sugar alcohols, a simple example being solketal. The acetonides of corticosteroid are used in dermatology, because their increased lipophil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroxyl
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy groups. Both the negatively charged anion , called hydroxide, and the neutral radical , known as the hydroxyl radical, consist of an unbonded hydroxy group. According to IUPAC definitions, the term ''hydroxyl'' refers to the hydroxyl radical () only, while the functional group is called a ''hydroxy group''. Properties Water, alcohols, carboxylic acids, and many other hydroxy-containing compounds can be readily deprotonated due to a large difference between the electronegativity of oxygen (3.5) and that of hydrogen (2.1). Hydroxy-containing compounds engage in intermolecular hydrogen bonding increasing the electrostatic attraction between molecules and thus to higher boiling and melting points than found for compounds that lack this f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racemate
In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. History The first known racemic mixture was racemic acid, which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. He manually separated the crystals of a mixture by hand, starting from an aqueous solution of the sodium ammonium salt of racemate tartaric acid. Pasteur benefited from the fact that ammonium tartrate salt that gives enantiomeric crystals with distinct crystal forms (at 77 °F). Reasoning from the macroscopic scale down to the molecular, he reckoned that the molecules had to have non-superimposable mirror images. A sample with only a single enantiomer is an ''enantiomerically pure'' or ''enantiopure'' compound. Etymology From racemic acid found in grapes; from Latin ''racemus'', meani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enantiomer
In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical antipode – is one of two stereoisomers that are non-superposable onto their own mirror image. Enantiomers are much like one's right and left hands, when looking at the same face, they cannot be superposed onto each other. No amount of reorientation will allow the four unique groups on the chiral carbon (see Chirality (chemistry)) to line up exactly. The number of stereoisomers a molecule has can be determined by the number of chiral carbons it has. Stereoisomers include both enantiomers and diastereomers. Diastereomers, like enantiomers, share the same molecular formula and are non-superposable onto each other however, they are not mirror images of each other. A molecule with chirality rotates plane-polarized light. A mixture of equals a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glyceride
Glycerides, more correctly known as acylglycerols, are esters formed from glycerol and fatty acids, and are generally very hydrophobic. Glycerol has three hydroxyl functional groups, which can be esterified with one, two, or three fatty acids to form mono-, di-, and triglycerides. These structures vary in their fatty acid alkyl groups as they can contain different carbon numbers, different degrees of unsaturation, and different configurations and positions of olefins. Vegetable oils and animal fats contain mostly triglycerides, but are broken down by natural enzymes (lipases) into mono and diglycerides and free fatty acids and glycerol. Soaps are formed from the reaction of glycerides with sodium hydroxide. The product of the reaction is glycerol and salts of fatty acids. Fatty acids in the soap emulsify the oils in dirt, enabling the removal of oily dirt with water. Partial glycerides are esters of glycerol with fatty acids, where not all the hydroxyl groups are esterified ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Esterified
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides are fatty acid esters of glycerol; they are important in biology, being one of the main classes of lipids and comprising the bulk of animal fats and vegetable oils. Esters typically have a pleasant smell; those of low molecular weight are commonly used as fragrances and are found in essential oils and pheromones. They perform as high-grade solvents for a broad array of plastics, plasticizers, resins, and lacquers, and are one of the largest classes of synthetic lubricants on the commercial market. Polyesters are important plastics, with monomers linked by ester moieties. Phosphoesters form the backbone of DNA molecules. Nitrate esters, such as nitroglycerin, are known for their explosive properties. '' Nomenclature Etymology The word '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diol
A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. The most common industrial diol is ethylene glycol. Examples of diols in which the hydroxyl functional groups are more widely separated include 1,4-butanediol and propylene-1,3-diol, or beta propylene glycol, . Synthesis of classes of diols Geminal diols A geminal diol has two hydroxyl groups bonded to the same atom. These species arise by hydration of the carbonyl compounds. The hydration is usually unfavorable, but a notable exception is formaldehyde which, in water, exists in equilibrium with methanediol H2C(OH)2. Another example is (F3C)2C(OH)2, the hydrated form of hexafluoroacetone. Many gem-diols undergo further condensation to give dimeric and oligomeric derivatives. This reaction applies to glyoxal and related aldehydes. Vicinal diols In a vicinal diol, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
