Carbonylation of o-, m-, and p-Methylbenzyl Alcohols using Supported Rhodium Catalyst

Abstract

The carbonylation of o-, m-, and p-methylbenzyl alcohols (MBAL) to o-, m-, and p-tolylacetic acids (TAA) using supported rhodium catalyst was carried out at 130 °C and under the CO pressure 3 x 103 kPa in the liquid phase using the autoclave connected to a gas reservoir. The products were analyzed by gas chromatography and gas chromatography-mass spectrometry. Both the conversion of MBAL and the selectivity to TAA under the present reaction conditions increased with reaction time, and the conversion reached to almost 100mol% after 60 min. In the initial stage of the carbonylation of o-MBAL, o-methylbenzyl o-tolylacetate (MBTA) was mainly produced, and the carbonylation of m-MBAL also proceeded in a similar manner. In contrast, bis(p-methylbenzyl) aether (DMBE) was formed in the initial stage of the carbonylation of p-MBAL. In any reactions, the selectivity of MBTA and DMBE gradually decreased as the reaction proceeded, and after 180 min, the corresponding TAA was obtained as a major product (selectivity 45-55 mol%).