Oxidation Reaction Mechanism of Alkynes by OH

A part of the OH-added radical isomerizes as in pathway (c), and forms vinoxy radical (CH2CHO) (Schmidt et al., 1985), but its succeeding reactions are not well known yet. 

The main products from the benzyl radical in the presence of NOx are known to be benzaldehyde and benzyl nitrate (Akimoto et al. 1978 Klotz et al. 1998 Calvert et al. 2002 Atkinson and Arey 2003), and their reactimi mechanism can be represented as. 

The direct meastirements of the rate constants of the reaction of hydroxymethyl cyclohexadienyl radical with O2 has been made using the UV absorption method (Sect. 5.2.10), and the values of 2.5 x 10 cm molecule for benzene (Bohn and Zetzsch 1999 Grebenkin and Krasnoperov 2004 Raoult et al. 2004 Nehr et al. 2011), 6.0 x 10 cm molecule s for toluene (Knispel et al. 1990 Bohn 2001) are reported. Therefore, most hydroxymethyl cyclohexadienyl radicals are thought to react solely with O2. Also, the unimolecular decomposition rate of cyclohexadienyl radical from benzene back to CgHg + OH has been reported as (3.9 1.3) s at 298 K (Nehr et al. 2011). 

The production of toluene 1,2-epoxide (C) and 2-methy oxepin (D) by the pathway (b) was proposed by Klotz et al. (2000). Their reaction rates with OH was found to be fast experimentally and theoretically, and they are thought to be one of the formation pathways to the open-ring compounds described below (Cartas-Rosado and Castro 2007). In the case of benzene, it has been reported that phenol is formed from the photolysis of benzene oxide and oxepin (Klotz et al. 1997), but the cresols are not formed from toluene 1.2-epoxide or 2-methyl oxepin (Klotz et al. 2000). 

The oxidation reaction mechanism of aromatic hydrocarbons in the atmosphere has not been established yet. Although the validation for the reaction model MCM 

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