GB802654A - Improvements in or relating to the production of naphthalenedisulphonyl chlorides - Google Patents

Abstract

1 : 5-Naphthalenedisulphonyl chloride is prepared by adding chlorosulphonic acid to a -naphthalene sulphonic acid, the amount of chlorosulphonic acid being in excess over the molar equivalent, allowing the reaction to proceed so as to form insoluble 1 : 5-naphthalenedisulphonyl chloride, and separating said chloride, which may have admixed therewith a minor proportion of 1 : 6-isomer, from the final reaction mixture. The a -naphthalene sulphonic acid may be prepared in a first stage by reacting naphthalene with sulphuric acid, preferably of between about 90 and 96 per cent concentration. The reaction with chlorosulphonic acid is preferably conducted at temperatures not in excess of 35 DEG C. Two methods of separation are specified. Method A gives a higher yield than method B of a product which contains some 1 : 6-isomer. Method B gives the substantially pure 1 : 5-isomer. These methods are illustrated in the examples. Naphthalene (1 mol.) is reacted with sulphuric acid (2 mols.) to give a mixture containing a -naphthalene sulphonic acid to which chlorosulphonic acid (8 mols.) is slowly added and the mixture allowed to react further at 30 DEG C. The 1 : 5-naphthalenedisulphonyl chloride crystals are separated from the reaction mixture by (a) hydrolysing the reaction mixture with ice, washing the insoluble material with water, filtering and drying, or (b) filtering the reaction mixture, washing the residue on the filter with water and drying; chlorosulphonic acid being recovered by distillation from the filtrate. Specification 802,655 is referred to.