An experimental and theoretical investigation of the triple fragmentation of CFClBr2 by photolysis near 250 nm

Photodissociation of CFClBr2+hν→CFCl has been shown to occur for λ<274 nm (436±2 kJ mol−1). G3 Ab initio calculations were performed to provide estimates of ΔfH for CFClBr2, CFClBr, and CFCl, which were calculated to be −188±5, −43±5 and +30±5 kJ mol−1, respectively. The dissociation energies (0 K) for sequentially breaking the C–Br bonds were calculated to be 257±5 and 183±5 kJ mol−1, respectively. The energy required to break both C–Br bonds was calculated to be 440±5 kJ mol−1, in excellent agreement with the experimental appearance threshold for CFCl. From the experimental appearance threshold, ΔfH (CFClBr2) is estimated to be −184±5 kJ mol−1.