PHOTOLYSIS OF MATRIX-ISOLATED ACRYLOYL CHLORIDE - 1,3-CHLORINE MIGRATION AND FURTHER EVOLUTIONS

Photolysis, at lambda greater than or equal to 310 nm (Delta E < 387 k J mol(-1)), of acryloyl chloride 1 isolated in argon matrixes at 10 K yields 3-chloro-1,2-propenone 4 through 1,3-chlorine migration. There is no evidence of cyclopropenone or propadienone formation. 4 is also synthesized by irradiation of 3-chloropropanoyl chloride (lambda great er than or equal to 230 nm) isolated in argon matrix at 10 K. Identifi cation is performed by comparison of experimental FT-IR spectrum with calculated ones tab initio calculations at the 6-31G* level). Irradia tion of 1 at lambda greater than or equal to 1 230 nm induces the phot olysis of 4 which breaks into CO and the postulated transient 2-chloro ethylidene 5 and/or into propadienone 2 complexed by HCl. The transien t 5 collapses to form ground-state vinyl chloride 6 by 1,2 hydrogen mi gration. In the next step, 2 loses CO to form a new transient assumed to be vinylidene 7 which yields ethyne by intramolecular isomerization process and vinyl chloride by intermolecular reaction with HCl trappe d in the same cage. CO, HCl, ethyne, and vinyl chloride are the final reaction products. Modeling of the 1,3 chlorine migration process from 1 using ab initio calculations at the MP2/6-31G level is performed i n the ground state (S-0) and the first singlet excited state (S-1). Th e reaction energy value for an S-1 (509 kJ/mol) state process is highe r than for an S-0 process (207.2 kJ/mol), these theoretical results su ggesting the reaction take place in the ground state.