Kinetic Studies of the Reaction of the Hydroxymethyl Radical with NO and NO2

Article abstract of DOI:10.1021/j100350a027

The absolute rate constant for the reaction CD2OH + NO has been measured from 230 to 373 K in a discharge-flow system.The decay of the CD2OH radical was monitored in excess NO by collision-free sampling mass spectrometry.At 298 K, k₁ = (2.2 +/- 0.4) x 10^-12 cm³ s^-1 (2?) independent of pressure from 0.5 to 1.5 Torr.For the 230-298 K interval, an activation energy of 1.2 kcal/mol is obtained, but k₁ does not appear to change within experimental error on going from 298 to 373 K.The absolute rate constant at 298 K has also been measured for the reaction CH2OH + NO2 by the same technique.The result is k₂ = (8.3 +/- 4.1) x 10^-12 cm³ s^-1 (2?).Qualitative detection was made of D2CO and H2CO as products of these reactions, but no evidence was obtained for the expected accompanying products HNO and HNO2 nor for the CD2OHNO and CH2OHNO2 adducts.It is suggested, partially by analogy with the CH2OH + O2 reaction, that the reaction mechanism in both cases involves initial formation of a vibrationally excited complex that, depending on reaction conditions, can dissociate back to reactants or, after isomerization, dissociate to products.Collisional stabilization of the addition complex may be feasible, but we have no evidence for this under the low-pressure condition of our experiments.The rate constants for reaction of CH2OH with O2, NO, and NO2 are briefly compared.