Investigating the Photodissociation Dynamics of CF 2 BrCF 2 I in CCl 4 through Femtosecond Time-Resolved Infrared Spectroscopy.

The photodissociation dynamics of CF 2 BrCF 2 I in CCl 4 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 CF 2 BrCF 2 or CF 2 ICF 2 radicals, respectively. All nascent CF 2 ICF 2 underwent further dissociation of I, producing CF 2 CF 2 with a time constant of 56 ± 5 ns. All nascent g -CF 2 BrCF 2 isomerized into the more stable a -CF 2 BrCF 2 with a time constant of 47 ± 5 ps. Furthermore, a -CF 2 BrCF 2 underwent a bimolecular reaction with either itself (producing CF 2 BrCF 2 Br and CF 2 CF 2 ) or Br in the CCl 4 solution (producing CF 2 BrCF 2 Br) at a diffusion-limited rate. The secondary dissociation of Br from a -CF 2 BrCF 2 was significantly slow to compete with the bimolecular reactions. Overall, approximately half of the excited CF 2 BrCF 2 I at 267 nm produced CF 2 BrCF 2 Br, whereas the other half produced CF 2 CF 2 . The excess energies in the nascent radicals were thermalized much faster than the secondary dissociation of I from CF 2 ICF 2 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.