| 摘要 |
Alpha hydroxycarboxylic acids are prepared by reacting organic compounds containing at least one terminal double bond between two carbon atoms at a temperature below 20 DEG C. with a nitric acid solution having an HNO3 concentration above 25 per cent by weight and containing a quantity of dinitrogen tetroxide above 10 per cent by weight of the nitric acid, the nitric acid being used in at least the stoichiometric amount required to convert the a -unsaturated organic compound to the corresponding a -hydroxycarboxylic acid. When 100 per cent nitric acid is employed the reaction is preferably subjected to subsequent hydrolysis conditions. The a -unsaturated starting compounds may contain functional groups such as hydroxyl, halide, cyano, ester, ether, keto and carboxyl groups. Specified starting materials are isobutylene, allylchloride, methyl methacrylate, methacrylonitrile, vinyl acetate, allyl alcohol, methyl allyl alcohol, methyl vinyl ketone, methyl vinyl ether, acrylic acid, methacrylic acid, butadiene, methyl pentadiene, diallyl, styrene, a -methylstyrene, para-divinylbenzene and a -vinylpyridine. The a -hydroxycarboxylic acids may be esterified with alcohols such as methanol, ethanol, propanol and butanol, and the esters may be dehydrated to the corresponding a :b -unsaturated carboxylic esters. Alternatively, the a -hydroxycarboxylic acids may be dehydrated to the corresponding a :b -unsaturated acids and, if desired, the latter may be subsequently esterified. The examples describe the conversion of isobutylene into a -hydroxyisobutyric acid, and the conversion of the latter compound into methyl a -hydroxyisobutyrate, methyl methacrylate and methacrylic acid is also described. |
