Cl[C:2]1[CH:10]=[CH:9][C:8]([N+:11]([O-:13])=[O:12])=[CH:7][C:3]=1[C:4]([OH:6])=[O:5].[C:14](=[O:17])(O)[O-:15].[Na+].[C:19](O)(=[S:22])CO.[Na]>CCOCCO>[C:14]([CH2:19][S:22][C:2]1[CH:10]=[CH:9][C:8]([N+:11]([O-:13])=[O:12])=[CH:7][C:3]=1[C:4]([OH:6])=[O:5])([OH:15])=[O:17]In a 5 liter flask equipped with an impervious agitator, a reflux refrigerant and a thermometer, there are introduced 146 g (0.72 mole) of 2-chloro-5-nitro-benzoic acid and 2200 ml of cellosolve. There is obtained a solution to which is added 181 g of sodium bicarbonate and 66 g of thio-glycolic acid. The mixture is refluxed. There is very rapid precipitation of the sodium salt of the carboxymethylthio acid formed. After 3 1/2 hours of reflux, the heating is stopped, and the sodium salt is cooled, drained and washed on a filter with 200 ml of cellosolve. This salt is then redissolved in water and the acid is precipitated with 145 ml of concentrated hydrochloric acid. It is drained, washed with water until the chloride ions are eliminated and dried at 50° C. There are obtained 159 g (yield: 86%) of 2-carboxymethylthio-5-nitro-benzoic acid (m.p.: 216°-217° C).
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