Preparation of sulphophenyl esters

摘要

Sulphophenyl esters can be made amongst other routes by reacting an acyl halide with a phenol sulphonate salt, but it has been suggested in the prior art that there are substantial problems or disadvantages associated with carrying out the reaction in the presence of an organic solvent such as gelation of the reaction medium or excessive reaction times. In the present invention, the process employs as organic solvent high boiling point primarily aliphatic hydrocarbons which forms with linear acyl halide a reaction medium in which products of high and/or improved purity and/or yield are obtainable without gelation and in reasonable reaction periods, especially between C6-C10 linear acyl chlorides and sodium phenol sulphonate. It has been found advantageous to pre-dry the phenol sulphonate salt by heating it when dispersed in a high boiling aliphatic or aromatic hydrocarbon solvent such that water and solvent are co-removed, with the result that in a subsequent esterification reaction with acyl halide an improvement in yield and/or purity of the sulphophenyl ester can be achieved.