Gas-phase reactions of atomic chlorine with vinyl fluoride

The addition of thermal chlorine atoms of vinyl fluoride has been studied over the pressure range from 50 to 4000 torr using thermalized /sup 38/Cl atoms from neutron irradiation of CClF/sub 3/. Thermal chlorine atoms show a preference for addition to CH/sub 2/ vs. CHF in CH/sub 2/ = CHF of 1.9 +/- 0.1 at 20/sup 0/C, and a total rate constant for the sum of the two addition reactions of (1.85 +/- 0.20) x 10/sup -10/ cm/sup 3/ molecule/sup -1/ s/sup -1/. Experiments carried out over the temperature range from 232 to 338 K show essentially no change in total reactivity by addition to CH/sub 2/ = CHF relative to abstraction of H from HI. The relative addition to the two ends of CH/sub 2/ = CHF changes over this temperature range, consistent with a lower activation energy for addition to CH/sub 2/ by 500 to 700 cal/mol. In contrast, the only literature value for a theoretical estimate of this preference for anti-Markownikoff addition gives an activation energy difference of 5400 cal/mol in CH/sub 2/ = CHF. The total rate constant for addition to CH/sub 2/ = CHF is the same within experimental error as for addition to CH/submore » 2/ = CH/sub 2/. Reversible loss of /sup 38/Cl is observed from both CH/sub 2//sup 38/ClCHF and CH/sub 2/CH/sup 38/ClF* radicals at lower pressures, with decomposition equal to stabilization at about 230 and 160 torr, respectively. By analogy with these CH/sub 2/ = CHF observations, the addition of thermal /sup 38/Cl to CH/sub 2/ = CHBr is postulated to occur in comparable yields at both ends of the molecule, rather than with a strong preference for addition at the CH/sub 2/ end. 25 references, 5 figures, 2 tables.« less