The kinetics and mechanism of the methylation of some phenols and the resolution of p-chlorbenzhydrol.

The bimolecular nature of the reaction between monalkyl sulphate ion and hydroxide ion is confirmed. Kinetic expressions have been derived for two simultaneous second order reactions in which one reactant is common to both reactions and the concentrations of the other two differ widely. The derived kinetic expressions have been applied to the reaction between monoalkyl sulphate ion and phenoxide ion in which the reaction of the former with hydroxide ion proceeds simultaneously. The bimolecular nature of the reaction is confirmed. The velocity of both reactions is greatly reduced on passing from methyl to ethyl sulphate. The effect of substituents in the phenol nucleus is in the anticipated direction, electron-attracting substituents decreasing the velocity and electron-donating substituents increasing it. Substituents in the ortho position exhibit a pronounced steric effect. The results of Hodgson and Nixon who determined the yield of anisole produced by reacting dimethyl sulphate with a series of substituted phenols under standard conditions are misleading. Owing to the superposition of two reaction mechanisms the yields of anisole are not a true measure of the reactivities of the various phenols. The normal procedure for the methylation of phenols with dimethyl sulphate is discussed. A mechanism is proposed for the methylation of phenols via the acetate by the method of Freudenberg. p-Chlorbenzhydrol has been resolved into its optical isomers by fractional crystallisation of the brucine salt of its hydrogen phthalic ester from ethyl acetate. Attempts to esterify 2:4:6-trimethoxybenzhydroI resulted in failure. This is attributed to ths similarity between this carbinol and tertiary alcohols which latter cannot be esterified by this method