GB846906A - Improvements in or relating to the production of acetals and dibasic acids therefrom - Google Patents

Abstract

Acetals are obtained from unsaturated fatty acids containing one or more =C-C-C= units by treating the fatty acids or their alkyl esters with a gas containing ozone, e.g. ozonised air, at a temperature between -50 and +130 DEG C. in the presence of an aliphatic primary alcohol having 1-4 carbon atoms and submitting the resulting solution to catalytic hydrogenation at a temperature between -10 and +60 DEG C., adding a little mineral acid to accelerate acetal formation and recovering the acetals from the alcoholic solution by distillation, after neutralising the free acid. The acetals so obtained may be converted to dicarboxylic acids by submitting them to acid hydrolysis to convert them into aldehydes and then to oxidation to convert them into acids ; any esterified groups may be converted to carboxylic groups by hydrolysis. In the examples : (a) a solution of methyl linoleate in methyl alcohol is treated with ozonised air, the product is catalytically hydrogenated, sulphuric acid is added and the product is neutralised with potassium carbonate; a mixture of malondialdehyde tetramethyl acetal, caproaldehyde dimethyl acetal and methyl azelate semi-aldehyde dimethyl acetal is obtained; and (b) a mixture of methyl esters of linseed oil fatty acids is treated by the process of (a) to give a mixture of malondialdehyde tetramethyl acetal, methyl azelate semialdehyde dimethyl acetal, pelargonaldehyde dimethyl acetal, caproaldehyde dimethyl acetal and propionaldehyde dimethyl acetal. The methyl azelate semialdehyde dimethyl acetal prepared as in (a) or (b) is hydrolysed with sulphuric acid and then treated with ozonised air ; the resulting solution of the half esteris saponified with caustic soda, cooled and acidified to give azelaic acid. Specifications 642,830 and 643,041 are referred to.