PREPARATION OF 3,3-DIMETHYLBUTYRIC ACID

PURPOSE:To obtain the titled compound useful as a raw material for agricultural chemicals, particularly a herbicide, in high yield and purity, by reacting a compound capable oif forming trimethylcarbonium ions with vinylidene chloride in the presence of sulfuric acid in a specific concentration or above. CONSTITUTION:A compound capable of forming trimethylcarbonium ions, e.g. tert-butanol, a lower fatty acid ester thereof, tert-butyl lower alkyl ether, tert- butyl halide or isobutylene, is reacted with vinylidene chloride in the presence of sulfuric acid in a concentration of preferably 92% or above, preferably 92- 98%, preferably at 0 deg.C or below, particularly -20-+0 deg.C, to give 3,3-dimethylbutyric acid very industrially and advantageously on an industrial scale without requiring apparatuses, e.g. large-scale recovery apparatuses, apparatuses for safety measures or rectifying apparatuses and using an expensive catalyst, e.g. boron trifluoride.