The Quaternization of Substituted N, N-Dimethylanilines with Benzyl Bromide

Abstract

The rates of quaternization of substituted N, N-dimethylanilines with benzyl bromide were measured at 30, 45 and 60°C in dimetylformamide (DMF). The effect of substituents on the reactivity of dimethylaniline and the existence of linear free energy relationship were discussed.
The kinetic data are shown in Table 1. The rate constants k are in the range 0.203∼78.1 X 10-4 1 sec' (45°C) and increase with the electron repelling ability of substituents. The values of the activation energy E are 6.5-10 kcal/mol and the activation entropy are -42∼-60 e. u., and the isokinetic relationship is observed between them as shown in Fig.2. Hammett equation using a as substituent constants is given by log k=- 1.92 α -2.874 (45°C).
As shown in Fig.3 the deviations from the Hammett correlation are found for m-dimethylaminophenol and p-substituted dimethylanilines substituted with formyl, benzoyl, nitro and methoxyl groups at n-position. The deviations are considered to be attributed to the conjugative interaction between the reaction center and these substituents and to the solvent effect of DMF on the substituent constants of these groups.
† Kinetic Studies on the Quaternization of Tertiary Amines.