Process for preparing 4-fluoro-3-trifluoromethylphenol

摘要

Disclosed is a process for preparing 4-fluoro-3-trifluoromethylphenol from 4-fluoro-3-trifluoromethylaniline, which comprises the steps of (1) using about 1 to 20 parts by weight of water based on 1 part by weight of 4-fluoro-3-trifluoromethylaniline in the presence of sulfuric acid to obtain 4-fluoro-3-trifluoromethylaniline sulfate; (2) subjecting the obtained 4-fluoro-3-trifluoromethylaniline sulfate to a diazotization reaction by using a diazotizing agent to obtain an aqueous solution containing about 8 to 25% by weight of a 4-fluoro-3-trifluoromethylbenzene-diazonium salt where a sulfuric acid concentration after diazotization is about 30 to 70% by weight in terms of the amount of sulfuric acid added, and the amount of water used is about 1 to 20 parts by weight based on 1 part by weight of 4-fluoro-3-trifluoromethylaniline; and (3) hydrolyzing the obtained 4-fluoro-3-trifluoromethylbenzenediazonium salt where a sulfuric acid concentration is about 30 to 70% by weight in terms of the amount of sulfuric acid added in a copper sulfate aqueous solution.