REACTION BETWEEN NO3 AND CH2O IN AIR: A DETERMINATION OF THE RATE CONSTANT AT 295+/-2 K.

Article abstract of DOI:10.1021/j100320a053

The reaction between NO3 and CH2O was studied in a 450-L glass/Teflon chamber by using FT-IR spectroscopy as the analytical technique.NO3 was obtained in equilibrium with N2O5 introduced from evaporation of the solid phase into the cell or generated in the cell itself by reacting NO2 with O3.Experiments were performed in both cases at 295+/-2 K and 740 Torr in purified air. (13)CH2O was used to avoid spurious effects on the measured CO; (13)C(18)O was introduced to estimate the OH radical concentration in the system from the buildup of the oxidation product (16)O(13)C(18)O. (13)CH2O, (13)C(16)O, N2O5, O3, NO2, and H(13)COOH time-dependent concentrations were measured and the data fitted on the basis of a model involving 31 reactions, with the aid of the FACSIMILE computer program.A rate constant for the reaction NO3+CH2O equal to (5.4+/-1.1)*1E-16 cm³ molecule^-1 s^-1, at 295+/-2 K and 740 Torr, has been obtained assuming for the reactions N2O5<*>NO3+NO2 an equilibrium constant equal to 5.3*1E10 molecules cm^-3.Significant differences have been found between the measured concentrations of OH and HCOOH with respect to those predicted by the model.In the framework of this study, the absolute strength of the ν₆ band of H(12)COOH (1045-1150 cm^-1) has been measured equal to (3.48+/-0.5)*1E-17 cm molecule^-1.