process for the production of m - or p - trifluormethylbenzoesäure from hexafluorxylol

摘要

The invention relates to a process for the preparation of trifluoromethylbenzoic acid from alpha , alpha , alpha , alpha ', alpha ', alpha '-hexafluoroxylene, which is a relatively inexpensive compound, in high yield. According to the invention, this compound is reacted with a strong acid in sulphuric acid, where at least some of this is fuming sulphuric acid. The use of fuming sulphuric acid as the strong acid is best. The reaction temperature is advantageously from room temperature to 150@C, temperatures below 100@C being preferred. In the process according to the invention, one trifluoromethyl group of the hexafluoroxylene is hydrolysed, unless the strong acid is present in a large excess.