Equilibration of benzene derivatives: Part II. t‐Butyl‐ and i‐Propyl‐benzenes

Abstract

AbstractLiquid phase isomer and transalkylation equilibria were determined for some t‐butyl‐ and i‐propyl‐benzenes containing an alkyl or halogen substituent, using aluminium bromide as the catalyst.Isomer equilibria contained low or zero proportions of ortho‐isomers. Meta‐2 para ratios ranged from 0.6 (di‐t‐butylbenzenes) to 2.0 (t‐butylfluorobenzenes). In all cases, more than 50% of meta isomer was present.Transalkylation (= disproportionation) equilibrium constants are probably governed mainly by electrostatic substituent interactions, favouring the presence of two groups having opposite polarities within the same molecule. Thus, for processes m‐Z‐C6H4R + C6H5H ⇄ C6H5Z + C6H5R, the extremes are 0.8 (disproportionation of m‐di‐t‐butylbenzene) and 2.4 (for m‐t‐butylchlorobenzene).The results may be interpreted along the same general lines as those for bromobenzenes reported on earlier1.