Infrared absorption of 3-propenonyl (center dot CH2CHCO) radical generated upon photolysis of acryloyl chloride [CH2CHC(O)Cl] in solid para-H-2

Abstract

Irradiation at 193 nm of a p-H-2 matrix containing acryloyl chloride CH2CHC(O)Cl at 3.2 K yielded infrared absorption lines at 3143.6 (nu(1)), 3057.0 (nu(2)), 3048.0 (nu(3)), 2103.1 (nu(4)), 1461.0 (nu(5)), 1349.8 (nu(6)), 1223.7 (nu(11)+nu(12) or 2 nu(12)), 1092.8 (nu(8)), 918.1 (nu(9)), 691.0 (nu(10)), 624.3 (nu(11)), and 597.1 (nu(12)) cm (1) that are assigned to the 3-propenonyl (center dot CH2CHCO) radical. The assignments are based on the photolytic behavior and a comparison of observed vibrational wavenumbers and infrared intensities with those predicted with the B3PW91/aug-cc-pVDZ method. The observation is consistent with a major radical formation channel CH2CHCO + Cl followed by escape of the Cl atom from the original p-H-2 cage. The observation of 3-propenonyl (center dot CH2CHCO) radical but not 3-propenalyl (s-cis- or s-trans-CH2CH(C) over dotO) radical indicates that the former is the most stable isomer and that the barrier heights for conversion from s-cis- or s-trans-CH2CH(C) over dotO to center dot CH2CHCO are small. (C) 2013 AIP Publishing LLC.