The kinetics and mechanisms of organic reactions in liquid ammonia

Abstract

Liquid ammonia is a potentially useful solvent for a variety of organic reactions and so understanding the kinetics and mechanisms of these processes is important. In contrast to the hydrolysis rates of the substituted benzyl halides in water which vary 107-fold, the rates of the solvolysis of substituted benzyl chlorides in liquid ammonia at 25 °C have little or no dependence upon ring substituents and vary only 2-fold between 4-methoxy- and 4-nitro- derivatives. The Hammett ρ-value is practically zero, which suggests there is no significant charge developed on the central carbon in the transition state. Activation energies for solvolysis of 4-nitro-, 4-methoxy-, 4-chloro- and unsubstituted benzyl chloride in liquid ammonia vary from 40.3 to 43.8 kJ mol−1 in the order of NO2 99%) selectivity towards O-benzylation of phenoxide ion, and with 1,2,4-triazolate anion gives predominantly (92%) substitution in the 1-position.