GB574645A - Preparation of carbonic acid esters - Google Patents

Abstract

Carbonic acid esters are prepared by reacting a dihaloformate of a glycol with a saturated monohydroxy alcohol containing 1-3 carbon atoms such as propyl alcohol. An alkaline reagent may be present and a diluent such as water, acetone, carbon tetrachloride or dioxane may also be added. In the examples: (1) ethylene glycol bis-chloroformate is added to a mixture of methyl alcohol and pyridine. The product is acidified with sulphuric acid, washed successively with dilute sulphuric acid, caustic soda and water, excess methyl alcohol evaporated and the ethylene glycol bis-(methyl carbonate) purified by vacuum distillation; (2) ethyl alcohol is added to a mixture of calcium carbonate and ethylene glycol bis-chloroformate which is heated under reflux with stirring. Ethyl alcohol is removed by evaporation and the product washed with dilute hydrochloric acid and water; (3) ethylene glycol bis-chloroformate, isopropyl alcohol, benzene and calcium carbonate are heated gradually under reflux. The product is washed with dilute hydrochloric acid and water and distilled under atmospheric pressure and finally under vacuum, (4) methyl alcohol is added to a mixture of diethylene glycol bis-chloroformate and pyridine with stirring. The product is washed with dilute acid, distilled and decolourized with activated charcoal. Other dichloroformates which may be used include those of alkylene glycols such as tri-, tetra- and pentamethylene glycols, and propylene glycol, and polyglycols such as tri-and tetraethylene glycols, di-, tri- and tetrapropylene glycols and polybutylene glycols. These may be prepared by reacting the glycol with phosgene. Other dihaloformates such as the dibromoformates may also be used. Other alkaline reagents which may be present include organic bases such as aniline, dimethyl aniline and quaternary ammonium bases such as tri-methyl phenyl ammonium hydroxide or inorganic bases such as the oxides, hydroxides and carbonates of alkali metals, e.g. sodium and potassium, or of the alkaline earth metals, e.g. calcium, barium, strontium and magnesium. The Specification as open to inspection under Sect. 91 (4) describes the reaction of polyhaloformates derived from polyhydroxy aliphatic compounds in general (many other than glycols being specified) with hydroxy compounds including high molecular weight, unsaturated, aromatic, polyhydric and/or substituted alcohols (examples of all of which are specified). The detailed examples include reactions of methallyl, allyl and 2-chloroallyl alcohols with dichloroformates. This subject-matter does not appear in the Specification as accepted.