Method of manufacture of the hydroxy - 4, dimethoxy - 3,5 from the benzoic acid, benzoic 3,4,5 trimethoxy -

摘要

P the invention relates to a method of manufacture of the hydroxy - 4, dimethoxy - 3,5 benzoic acid from the acid trimethoxy - 3,4,5 benzoic acid / p & & p & the demethylation of the acid trimethoxy - 3,4,5 benzoic acid in the presence of an excess of alkali metal hydroxide in a quantity of ethylene - glycol just sufficient to obtain a heterogeneous medium which is sufficiently fluid during the operation, while distilling off the monomethyl ether of ethylene - glycol and water formed during their formation and the acid hydroxyl - 4 dimethoxy - 3,5 benzoic acid obtained is separated by acidification by means of a strong acid and crystallization. / p & & p & application to the manufacture of the hydroxy - 4 dimethoxy - 3,5 benzoic acid / p