Method for preparing 4-alkyl-2-hydroxy-3,5-dichlorobenzene sulphonic acids

摘要

The invention is related to a method for preparing 4-alkyl-2-hydroxy-3,5-dichlorobenzene sulphonic acids by sulphonating 4-chloro-3-alkylphenol and by chlorinating 4-alkyl-2-hydroxy-5-chlorobenzene sulphonic acid present in an acidic reaction mixture. According to the invention, chlorination is carried out by adding, to the acidic reaction mixture, salts of hypochlorous and/or chloric acids and, when needed, hydrochloric acid or its salt.