Dissociation dynamics and thermochemistry of chloroform and tetrachloroethane molecules studied by threshold photoelectron photoion coincidence

Threshold photoelectron photoion coincidence (TPEPICO) technique has been employed to determine accurate dissociative photoionization onsets for chloroform and 1,1,2,2-tetrachloroethane molecules. Our 0 K onsets for these reactions are CHCl3 + hv → CHCl2+ + Cl (11.500 ± 0.007 eV); C2H2Cl4 + hv → C2H2Cl3+ + Cl (11.565 ± 0.010 eV) and C2H2Cl4 + hv → CHCl2+ + CHCl2 (11.669 ± 0.030 eV). The well established heat of formation of CHCl3 was used as an anchor and the measured dissociation energies were used to determine the heats of formation, ΔfH298Ko in kJ/mol, of the following species: CHCl2+ (888.9 ± 1.3), CHCl2 (87.1 ± 1.6), C2H2Cl4 (−152.7 ± 3.5), and C2H2Cl4+ (918.3 ± 5.9). Our results also made possible the determination of reliable 298 K bond enthalpies for: CHCl2Cl (311.1 ± 2.0 kJ/mol), CHCl2H (400.6 ± 2.0 kJ/mol), and CHCl2CHCl2 (326.9 ± 4.1 kJ/mol).