Catalytic dimerisation of acrylonitrile.: I. Homogeneous catalysts from alkyl diarylphosphinites and dialkyl arylphosphonites Original Research Article

Acrylonitrile has been converted catalytically to the straight chain dimer, 1,4-dicyanobutene-1, for the first time with both high selectivity to the linear dimer and in high yield on acrylonitrile consumed. The catalyst is an aromatic phosphinite or phosphonite, in a reaction medium which contains alcohol, hydrocarbon and acrylonitrile, and which must be purified rigorously from traces of water and phenolic stabilisers normally present in commercial acrylonitrile, otherwise catalyst deactivation results. The catalysts were discovered during detailed investigations into the activities of related heterogeneous catalysts which had also been discovered to give high selectivities to the linear dimer, but in a poorly reproducible manner. The dimerisation is thought to proceed via the formation of ylid and betaine intermediates derived from the addition of the phosphorus derivative to acrylonitrile. The factors affecting catalyst performance and selectivity are discussed.