Aromatic sulfonation 32: Kinetic isotope effect of hydrogen in sulfonation and sulfonylation of benzene

The substrate kinetic isotope effects of hydrogen in the sulfonation and sulfonylation of benzene were determined by the competitive method, using mixtures of benzene and hexadeuterobenzene. For the sulfonation with chlorosulfuric acid, kH/kD = 1.7 ± 0.1 and 1.55 ± 0.1 for nitromethane as solvent at 25° and for dichloromethane at 0°, respectively; for the consecutive sulfonylations, kH/kD = 1.1 ± 0.1 and 1.3 ± 0.2, respectively. For the aluminum chloride catalyzed sulfonylation with p-toluenesulfonyl chloride at 25°, kH/kD = 1.5 ± 0.1 and 3.3 ± 0.2 for nitromethane and dichloromethane as the respective solvents.