Matrix isolation and theoretical study on the photolysis of trichloroacetyl chloride

UV photolysis of CCl3COCl has been investigated by infrared spectroscopy in cryogenic Ar and O2 matrices. In the Ar matrix, CCl4 and CO were found to be dominant products over Cl2CCO. The CCl3 and COCl species, observed as intermediates, indicated C–C bond cleavage. The C–C bond cleavage was also evidenced by the formation of ClC(O)OO in the O2 matrix. The marked difference in the photochemistry of matrix-isolated CCl3COCl from that of CH3COCl, where CH2CO is the predominant product, can be attributed to the triplet surface reaction of CCl3COCl, as supported by the present DFT calculations.