33 parts of diethyl sulphate are added to 20 parts of diethiolisophthalic acid
(MP 245°-247°C prepared by the reaction of isophthalylchloride with sodium
hydrogen sulphide) in 125 parts of 8% aqueous sodium hydroxide solution at
20°C and the mixture is then heated at 40°-50°C during one hour. The
mixture is then cooled and extracted with 250 parts of benzene, in three
portions. The benzene extract is washed with water and dried and the
benzene is distilled. The residue is then distilled under reduced pressure to
give diethyl dithioisophthalate, BP 210°-215°C/15 mm.
