Photodissociation of gaseous propionyl chloride at 248 nm by time-resolved Fourier-transform infrared spectroscopy

In one-photon dissociation of propionyl chloride at 248 nm, time-resolved Fourier-transform infrared emission spectroscopy is used to detect the fragments of HCl and CO in the presence of Ar. The inert gas Ar plays a role to enhance the internal conversion. The time-dependence of high-resolution HCl spectra yields a bimodal rotational distribution in the early stage. The total rotational and vibrational energy partitioned in HCl are evaluated to be 1.7 +/- 0.3 and 8.8 +/- 1.9 kcal/mol, respectively. The CO appearance indicates that HCl may be eliminated through a five-center mechanism accompanied with three-body dissociation of C2H2, HCl, and CO. A four-center mechanism forming HCl and CH3CH=CO also contributes to the HCl fragment with a feature of rotational bimodality. However, the probability for the HCl contribution from the hot Cl reaction is negligible. The reaction with CH4 is carried out to evaluate the HCl and Cl elimination rate constants. (C) 2010 Elsevier B.V. All rights reserved.