Kinetics on the carboxylation of cyclohexanone in dimethyl sulfoxide solution containing 1,8-diazabicyclo [5,4,0] undec-7-ene and carbon dioxide.

Abstract

Carboxylation of cyclohexanone (1) with carbon dioxide (CO2) has been investigated in a dimethyl sulfoxide (DMSO) solution containing 1,8-diazabicyclo [5, 4, 0] undec-7-ene (DBU). Effects of variables, such as concentration of 1 and DBU, pressure of CO2 and temperature, on the rate of formation of DBU salts of cyclohexanone-2-carboxylic acid (2) have been examined kinetically. The kinetic investigation suggests that carboxylation begins with the formation of a complex between DBU and CO2 (1:1) and that the transfer of CO2 from the complex to 1 to form 2 is the slow step. The rate is first order with respect to the concentration of 1 and DBU, but non-linear with respect to the pressure of CO2. The equilibrium constant of the formation of 2 (formulated as 1+CO2+DBU⥩2‧DBU) in DMSO has been determined at various temperatures. © 1978, The Japan Petroleum Institute. All rights reserved.