Can Anisole Be Nitrated Only With Nitric Acid?
Question
Nitration of anisole (methoxybenzene) is possible with concentrated nitric acid (HNO3) and also with diluted HNO3. The nitration of anisole in aqueous nitric acid in the concentration range of 25.18-31.38 mol% at temperatures in the range 293-328 K proceeds according to pseudo-first order kinetics, and values of the rate constant and activation energy were obtained.
The mechanism for the nitration is given as follows:
HNO3+H3O+↽−−⇀NO2++2H2O(1)(1)HNOX3+HX3OX+↽−−⇀NOX2X++2HX2O (1)
NO2++ArH↽−−⇀encounter pair(2)(2)NOX2X++ArH↽−−⇀encounter pair (2)
encounter pair↽−−⇀benzenonium ion−→−fastproducts (3)
The activation energy of the rate determination step decreases with increasing acid concentration.
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