Dissociations of gas-phase CHClF and CHCl2 radicals and cations following collisional electron transfer. A variable-time neutralization-reionization and ab initio study

Variable-time neutralization-reionization mass spectrometry is used to generate CHClF . and CHCl2 . radicals and to study their unimolecular dissociations within 0.4-4.1 mu s. Loss of Cl . is a major dissociation of CHClF . following collisional neutralizations with di-n-butyl ether, chlorobenzene, di-n-butylamine, aniline, and N,N-dimethylaniline, which range from 0.28 eV endoergic to 1.7 eV exoergic in the same series. Loss of H . also occurs, whereas loss of F . and eliminations of HF and HCl are unimportant. Dissociations of CHClF+ cations following collisional reionization of CHClF . show eliminations of HF and HCl and losses of F . and Cl . whose rate parameters depend on the nature of the neutralization target. Both CHCl2 radicals and ions undergo elimination of HCl and loss of Cl . whose rate parameters are distinguished by the variable-time measurements. Ab initio calculations at the G2(MP2) level of theory give the bond dissociation energies for C-H, C-Cl, and C-F in CHClF . as 307, 333, and 465 kJ mol(-1), respectively. Eliminations of HCl and HF have the lowest thermochemical thresholds, 217 and 225 kJ mol(-1), respectively, but overcome activation barriers. Franck-Condon effects in fast electron transfer are calculated to deposit 34 and 91 kJ mol(-1) in the vertically formed CHClF . and CHClF+, respectively.