Vapor phase hydrolysis of benzal chlorides having trifluoromethyl group on solid acid catalysts

Abstract

Benzaldehydes having trifluoromethyl group (1) were known to be prepared by hydrolysis of the corresponding benzal chlorides ( 2 ) with conc. sulfuric acid. However, this method is not favorable for the synthesis of 1 because of the formation of tary materials and the complexity of the reaction process. In order to overcome these disadvantages, vapor hydrolysis of 2 was investigated in the presence of solid acid catalysts. Metal oxides such as γ - Al 2O 3 and TiO 2 gave 1 but their lives of catalytic activities were not satisfactory. While activated carbon soaked in conc. sulfuric acid yielded 1 with a little amount of phthalic acids, metal chlorides supported on activated carbon gave 1 without hydrolysis of the trifluoromethyl group. Metal chlorides such as Fe(III), Mn(II) and Co(II) were the most effective in these reactions.