Selective rhodium catalysed synthesis of trans-1,4-hexadiene in polyethylene glycol 1000–water solvent systems

Abstract

trans-1,4-Hexadiene is of great importance in the production of functionalizable polymers and is employed in preparing ethylene-propylene-diene-monomer (EPDM) terpolymers. Synthesis of trans-1,4-hexadiene by the codimerization of 1,3-butadiene and ethylene has been studied since the 1960s and many transition metals were used as catalysts, e.g. rhodium, nickel, cobalt or ruthenium. Among them, only rhodium catalysed reactions gave the desired trans-1,4-hexadiene, however, only with low reaction rates. In this paper, a new combination of a rhodium catalyst with the polyethylene glycol 1000 (PEG1000)–water solvent system was studied and a high amount of trans-1,4-hexadiene was attained together with a 58% total conversion of ethylene and a 71% selectivity of 1,4-hexadiene.