GB802022A - Dioxolanes - Google Patents

Abstract

A 1,3-dioxolane is prepared by reacting a polyhydric alcohol with an aldehyde or ketone in the presence of a carboxylic acid having a dissociation constant not less than 5 X 10-2. The compound reacted with the polyhydric alcohol may be an aliphatic ketone such as acetone or methyl ethyl ketone, an aromatic ketone such as acetophenone or benzophenone, a cyclic ketone such as cyclohexanone or unsaturated ketone such as methyl vinyl ketone, methylisopropenyl ketone, or mesityl oxide, diacetone alcohol; or a saturated or unsaturated aliphatic or aromatic aldehyde. Preferred alcohols are glycols such as ethylene glycol, propylene glycol, butylene glycols, glycerol, glycerol monoacetin and glycerol a -chlorhydrin. When glycerol is used the formation of six-membered rings may be suppressed by the addition of copper salts to the reaction mixture. Suitable acids are those which have one or more electrophilic groups adjacent to the carboxyl group, e.g. dichloroacetic acid, trichloroacetic acid and oxalic acid. The reaction is preferably carried out at a temperature below 80 DEG C. When the reaction is complete the catalyst is neutralized, preferably with ammonia. The reaction may be carried out in the presence of inert dehydrating agents such as anhydrous sodium sulphate or anhydrous magnesium sulphate. In cases where the higher boiling and less water-soluble carbonyl compounds are used the reaction may be carried out by refluxing in the presence of an azeotropic entrainer such as benzene, toluene, petroleum spirit or methylene dichloride. In the examples: (a) glycerol is mixed with acetone, oxalic acid and anhydrous cupric sulphate are added and the mixture is heated to 45 DEG C.; 2,2-dimethyl-4-methylol-1,3-dioxolane is separated from the resulting mixture; and (b) glycerol is mixed with methylethylketone; oxalic acid and cupric sulphate are added with benzene and the mixture is refluxed; 2,2-dimethyl-4-methylol-1,3-dioxolane is separated from the resulting mixture.