New insights into the Ar-matrix-isolation FTIR spectroscopy and photochemistry of dichloroacetyl chloride, ClC(O)CHCl2: influence of O2 and comparison with gas-phase photochemistry

LUCIANA M. TAMONE; A. LORENA PICONE; ROSANA M. ROMANO

Journal of Photochemistry and Photobiology

Elsevier

Lugar: Amsterdam; Año: 2021 vol. 6

2666-4690

Photolysis products of dichloroacetyl chloride (DCAC)isolated in Ar matrix and in gas phase, in the absence and presence ofmolecular oxygen, were studied by means of FTIR spectroscopy. The samples wereexposed to light of different energy ranges (200-800, 280-320, 350-450 and 400-800nm). DCAC is photostable when irradiated with light of wavelengths above 400 nm,and gives dichloroketene after photolysis with light between 280-320 and350-450 nm. Exposure of DCAC to broad-band radiation (200-800 nm) producesdichloroketene as an intermediate photoproduct, and different 1:1 CHCl3:COmolecular complexes after further irradiation. HCl, CO and CHCl3were detected in gas-phase DCAC photolysis. ClC(O)CCl2CCl2Hmolecule was also proposed, in a mechanism that involve the insertion of :CCl2biradical into the C-C bond of DCAC. The photochemical reaction of DCACwith O2 in Ar matrix gives Cl2CO and CO2. Thesame photoproducts, together with HCl, were observed in the gas-phasephotochemical reaction. Additionally, the FTIR spectra of DCAC isolated insolid Ar were fully interpreted in terms of an equilibrium between syn (the H-C bondsyn with respect to the C=O bond) and gauche conformers.Some absorptions, which grow as the DCAC:Ar ratio increases, were attributed todimeric forms. The most stable dimer was predicted by DFT calculations ascomposed by two DCAC molecules with synconformations, interacting through two H-bonds in a structure with Ci symmetry.