Isomerisation of phosphabutyne and a photochemical route to phosphabutadiyne (HC3P), a phosphorus analogue of cyanoacetylene.

The photochemistry of phosphabut-1-yne, CH3CH2CP, was investigated by means of infrared spectroscopy assisted by theoretical (DFT) predictions. The UV-irradiated compound, isolated in a cryogenic argon matrix, undergoes isomerization and dissociation. Several isomers of phosphabutyne, in addition to phosphabutadiyne (HC3P), ethynylphosphinidene (HCCP), and phoshaethyne (HCP) are formed as the main photoproducts. Vibrational spectra of astrochemically relevant molecules HC3P and CH2CHCP (vinylphosphaethyne), have been detected and analyzed here for the first time.