The chlorosulfonic acid promoted a-iodination of some aliphatic acids in 1, 2-dichloroethane has been studied. In contrast to the bromination, the effect of substituents on the rate shows not only a polar effect but also a steric effect m view of Taft's equation: log krel= p, CE,+ SEE,, where po=-1.20 and 6= 1.55 at 80 “C. The transition state is discussed, which involves the electrophilic addition of I2 to a ketene intermediate. Aliphatic acids with less steric ...
