The conjugated process of carbon monoxide oxidation and cyclohexene hydrocarboxylation to cyclohexanecarboxylic acid

Abstract

The kinetic regularities of the conjugated process of the oxidation of carbon monoxide and the hydrocarboxylation of cyclohexene to cyclohexanecarboxylic acid have been studied. The copper(II) bromide addition allowed to stabilize the system and to increase selectivity due to the suppression of side reactions of the cyclohexene conversion and tetrahydrofuran. To achieve the acceptable rate and the selectivity of the transformation to cyclohexanecarboxylic acid it is advisable to use the palladium bromide concentration of 0.05 mol/L. To study the kinetic regularities the lower concentration of palladium bromide of 0.005 mol/L is required to ensure the system stability and the good reproducibility of results. The state of bromide complexes of palladium and copper under the conditions of conjugated catalytic synthesis of cyclohexanecarboxylic acid by the hydrocarboxylation of cyclohexene was studied by electron and infrared spectroscopy. It was found that during the conjugated process, copper exists in the form of copper(I) compounds, and palladium is present in the form of palladium(II) carbonyl complex. Hypotheses about the mechanism of this process were suggested. 24 two-route mechanisms of the carbon dioxide and the cyclohexanecarboxylic acid synthesis were obtained. Each of the 24 hypotheses spawned from one to three hypothetical mechanisms differing in the reversibility of the stages, the amount and the composition of intermediates accounted for in the material balance for the catalyst.

Keywords

• conjugated process, cyclohexene hydrocarboxylation, cyclohexanecarboxylic acid, electron spectroscopy, infrared specroscopy, hypotheses about the mechanism.