MAY, 1962 4-SUBSTITUTED a-CHLORO-3-BITIZOTOLUENES 1521 some years that the two branches of the Hammett plot do not result from grossly different mechanisms; in a number of cases second-order kinetics have been established throughout a series. In general the unsubstituted benzyl compound shows the minimum rate4 in the p-substituted series, although a variety of nucleophiles, lS2 solvents, 2 and ionic strength^,^ have been ...