Journal of Physical Chemistry A, Vol.105, No.9, 1423-1432, 2001
Kinetics of CH2ClO radical reactions with O-2 and NO, and the unimolecular elimination of HCl
The kinetics of the title reactions were investigated at 5-35 Torr total pressure and 265-306 K by UV flash photolysis and time-resolved mass spectrometry. The CH2ClO radical was generated by photolysis of NOCl in the presence of CH3Cl, O-2, and NO. Atomic chlorine from NOCl photodissociation abstracted H from CH3Cl acid initiated oxidation of CH2Cl radicals, leading to formation of CH2ClO. The CH2ClO radical reacted with both O-2 and NO, or underwent unimolecular elimination of HCl. The kinetics were determined from growth rates of HC(O)Cl and HCl. The rate coefficient of the CH2ClO + O-2 reaction was found to be independent of pressure, The temperature dependence can be expressed as: k(CH2ClO + O-2) = (2.0 +/- 0.7) x 10(-12) exp[-(934 +/- 128)/T] cm(3) molecule(-1) s(-1). The rate coefficients for the CH2ClO + NO reaction were found to be independent of both pressure and temperature, with the value k(CH2ClO + NO) = (2.7 +/- 0.6) x 10(-12) cm(3) molecule(-1) s(-1), obtained by averaging all rate coefficients determined over the experimental range of pressure and temperature. The rate coefficient for unimolecular elimination of HCl from CH2ClO was found to be pressure dependent, and well into the falloff. The unimolecular rate coefficient at 10 Torr can be expressed as (7.7 +/- 2.3) x 10(9) exp[-(4803 +/- 722)/T]s(-1).