Laser-Induced Fluorescence of the CHClCHO Radical and Reaction of Oxygen Atoms with Halogenated Ethylenes

A new laser-induced fluorescence spectrum has been observed in the region 320−360 nm. Since this spectrum is observed when reacting oxygen atoms with chlorinated ethylenes such as CH<INF>2</INF>CHCl, CH<INF>2</INF>CCl<INF>2</INF>, CHClCHCl, and CHClCHF and also when chlorine atoms react with chloroacetaldehyde, the fluorescing molecules are identified as cis- and trans-2 chlorovinoxy radicals (cis- and trans-CHClCHO). From an analysis of the laser-induced single vibronic level fluorescence, some of the vibrational frequencies can be assigned for the ground electronic state (&Xtilde; ²A‘ ‘):  ν<INF>3</INF>(CO str) = 1567, ν<INF>4</INF>(CH rock.) = 1380, ν<INF>5</INF>(CH rock.) = 1309, ν<INF>6</INF>(CC str) = 1060, ν<INF>7</INF>(CCl str) = 820, ν<INF>8</INF>(CCO bend.) = 677, and ν<INF>9</INF>(CCCl bend.) = 220 cm^-1 for cis-CHClCHO; ν<INF>3</INF> = 1581, ν<INF>4</INF> = 1379, ν<INF>5</INF> = 1267, ν<INF>6</INF> = 1145, ν<INF>7</INF> = 942, ν<INF>8</INF> = 472, and ν<INF>9</INF> = 324 cm^-1 for trans-CHClCHO. Some of the vibrational frequencies for the excited &Btilde;²A‘ ‘ state also are assigned. These vibrational assignments are supported by ab initio calculations. The calculated geometries of the cis- and trans-CHClCHO radicals are planar in the ground state and slightly nonplanar in the excited state. Radiative lifetimes of the excited cis- and trans-CHClCHO radicals are also reported. The experimental results showed that the C−C−O skeleton and spectroscopic character of the cis- and trans-CHClCHO are closer to those of CH<INF>2</INF>CHO than to those of CH<INF>2</INF>CFO. The mechanisms of the O + halogenated ethylene reactions are discussed.