The SN mechanism in aromatic compounds. Part 42. para-Substituent effects of some groups with a CN function joined to the ring. A possible inverse α-effect

Abstract

Kinetic measurements of reactions of N₃^–, OH^–, or OMe^– with a series of 4-chloro-3-nitro-X-benzenes were used to obtain values of Hammett substituent constants (σ^–) for p-CHNPh, 0.65 and 0.70; p-CHNC₆H₄NO₂-p, 0.79; p-CHNOH, 0.55; p-CHN(O^–)Ph, 0.95. These values, plus those for p-NNPh, 0.66; p-NN(O^–)Ph, 0.62; p-CHO, 0.93; p-CN, 1.00; p-NO₂, 1.27, are analysed and discussed. The possible existence of an inverse α-effect is indicated.