Directive Effects in Electrophilic Aromatic Substitution (“Ipso Factors”). Nitration of Haloanisoles

Abstract

The kinetics of the nitration of anisole and p-iodo-, p-bromo-, and p-chloroanisole have been studied. The relative reactivities of the ortho positions of these compounds are 1:0.119:0.077:0.069. In acetic anhydride attack by NO2+ para to the methoxyl occuss to the extent of 30.6, 40, 31, and 28% of total attack. Therefore, ifx, the ipso partial rate factors for the halogens iodine, bromine, and chlorine, are 0.18, 0.079, and 0.061. These values represent the directive effect of the halogen on the rate of attack, not ortho, meta, or para to the substituent, but directly at the position bearing the substituent. © 1971, American Chemical Society. All rights reserved.