Hydrogen abstraction dynamics in solution studied by picosecond infrared spectroscopy

Solution-phase bimolecular reactions are observed directly for the first time using transient infrared absorption spectroscopy. Laser photolysis of Cl2 using a UV pulse at 355 nm creates chlorine radicals in neat cyclohexane solution and initiates a hydrogen abstraction reaction to form HCl or DCl (in deuterated solvent) as products. Picosecond infrared pulses at 3.3 or 5 μm probe the vibrational state populations to determine the time development of the product formation. The observed reaction rate of HCl formation is (5.6 ± 1) × 109 M−1 s−1, which is approximately 14±6 times slower than previously reported gas-phase kinetic results.