H. Niki

An FTIR study of mechanisms for the HO radical initiated oxidation of C2H4 in the presence of NO: detection of glycolaldehyde

Using the long-path FTIR method, glycolaldehyde, CH2(OH)CHO, was detected among the products in photolysis of mixtures containing C2H4, NO and RONO (R = alkyl group) at ppm concentrations in air. The results suggest the occurrence of both unimolecular dissociation and O2 reaction of an oxy-radical, CH2(OH)CH2O, formed in the HO-initiated oxidation of C2H4 in the presence of NO.

FTIR spectroscopic study of the gas-phase reaction of HO2 with H2CO

The reaction of formaldehyde with HO2 radicals in the presence of O2 and NO2 has been studied in a 420 l reaction chamber at 0° C in 533 mbar of synthetic air. Reactants and products were measured by FTIR absorption spectrometry-Additional evidence is presented for the formation of the HOCH2OO radical as the primary reaction product, by the IR spectroscopic identification of its NO2 recombination product HOCH2OONO2. By computer simulation of the concentration-time profiles of HO2NO2, H2CO and HOCH2OONO2, the rate constants (0°C, 533 mbar, M = air) k1 = (1.1 ± 0.4) × 10-13 cm3 s-1 and k-1 = 20-10+20 s-i have been derived for the reactions (1, -1) HO2 + H2CO ⇌ HOCH2OO.

Further IR spectroscopic evidence for the formation of CH2(OH)OOH in the gas-phase reaction of HO2 with CH2O

Abstract Two O-H stretch bands at 3647.5 and 3598.3 cm−1 have been observed for the previously reported “metastable species” formed by HO2-CH2O interactions. These bands are consistent with the presence of an OH and an OOH group and provide support for the earlier tentative identification of hydroperoxy-hydroxy-methane, CH2(OH)OOH, formed via CH2O + HO2 → CH2(OH)OO, CH2(OH)OO + HO2 → CH2(OH)OOH + O2. This compound is relatively stable in the dark at 25°C.