Liquid Phase Synthesis of sec-Butyltoluenes by Alkylation Reaction of Toluene with 1-Butene

Abstract

As to synthesis of sec-butyltoluene(SBT) giving the para isomer selectively by alkylation of toluene with 1-butene, the suitable catalysts and optical conditions have been investigated. In this paper, the experimental results of liquid phase reaction utilizing seme Friedel-Crafts catalysts (phosphorus pentoxide, metal halides and so on) are presented.Since the SBT isomers have not been completely identified in previous reports, each one was prepared from the corresponding isomer of brometoluene and was used to identify the reaction products.It was found that phospherus pentoxide gave the para isomer in higher selectivity than the other catalysts. Yields of SBT based on charged 1-butene were 85N90%e and a distribution of the isomer (p-: m-: o-) was 56: 17: 27, when charged molar ratios of toluene, phosphorus pentoxide and 1-butene were 6, O.21 and O.56 at 100Av1200C, respectively. Under these conditions the reaction rate was found to be pseudo-first erder with respect to 1-butene ancl the specific reaction rate was 7800 exp(-9950/R T) min-1.From the result of isomer distributions and anhydrous reaction condition, it might be concluded that the reaction proceeds both through the carbonium ion mechanism with a trace of water and through a mechanism containing direct, coordination cemplexes between 1-butene and the catalyst.