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.