Investigating the Photodissociation Dynamics of CFBrCFI in CCl through Femtosecond Time-Resolved Infrared Spectroscopy.

The photodissociation dynamics of CFBrCFI in CCl at 280 ± 2 K were investigated by probing the C-F stretching mode from 300 fs to 10 μs after excitation at 267 nm using time-resolved infrared spectroscopy. The excitation led to the dissociation of I or Br atoms within 300 fs, producing the CFBrCF or CFICF radicals, respectively. All nascent CFICF underwent further dissociation of I, producing CFCF with a time constant of 56 ± 5 ns. All nascent -CFBrCF isomerized into the more stable -CFBrCF with a time constant of 47 ± 5 ps. Furthermore, -CFBrCF underwent a bimolecular reaction with either itself (producing CFBrCFBr and CFCF) or Br in the CCl solution (producing CFBrCFBr) at a diffusion-limited rate. The secondary dissociation of Br from -CFBrCF was significantly slow to compete with the bimolecular reactions. Overall, approximately half of the excited CFBrCFI at 267 nm produced CFBrCFBr, whereas the other half produced CFCF. The excess energies in the nascent radicals were thermalized much faster than the secondary dissociation of I from CFICF and the observed bimolecular reactions, implying that the secondary reactions proceeded under thermal conditions. This study further demonstrates that structure-sensitive time-resolved infrared spectroscopy can be used to study various reaction dynamics in solution in real time.