Direct Measurement of the Equilibrium Constants of the Reaction of Formaldehyde and Acetaldehyde with HO2 Radicals

摘要: Rate and equilibrium constants for the reaction of HO_2 with formaldehyde CH_2O + ↔ HOCH_2O_2 and acetaldehyde CH_3CHO CH_3CH(OH)O_2 have been directly measured. The concentration radicals was followed in a time-resolved method by coupling cw-CRDS (cavity ringdown spectroscopy) to laser photolysis. CH_2O (R1) measured at 50 Torr helium over temperature range 292–306 K, whereas (R2) He but only 294 K. observed decay profiles were modeled take into account secondary chemistry, especially that products, hydroxyl-peroxy radical adducts. rate forward back reactions 297 K found be k_1 = (3.3 ± 0.6) × 10^(−14) cm^3 molecule^(−1)s^(−1) k_(−1) (55 5) s^(−1), respectively, both roughly factor two slower than earlier measurements (possibly due falloff effects), while constant K_1 (6.0 1.8) 10^(−16) molecule^(−1) good agreement earlier, more indirect determinations. K_2 (1.7 0.5) 10^(−17) k_2 (1.5 0.75) k_(−2) (900 450)s^(−1).