Radicals n-propylperoxy

Figure 2 The figure shows 1,5-H atom transfers in (from left) n-propylperoxy radical, 1-butoxy radical, and n-pentyl radical, used to investigate the corresponding isomerizations in larger alkylperoxy radicals, alkoxy radicals, and alkyl radicals, respectively.

Merle JK, Hayes CJ, Zalyubovsky SJ, Glover BG, Miller TA, HadadCM. Theoretical determinations of the ambient conformational distribution and unimolecular decomposition of n-propylperoxy radical. J Phys Chem A. 2005 109 3637-3646. Vereecken L, Peeters J. The 1,5-shift in 1-butoxy a case study in the rigorous implementation of transition state theory for a multirotamer system. / Chem Phys. 2003 119 5159-5170. 

Reaction of butanal with all three reactive species leads primarily to the formation of the butanoyl radical by abstraction of the aldehydic H-atom. Papagni et al. (2000) noted an increase in the rate coefficient of OH with butanal, compared with that with propanal, which is compatible with the sensitization of the C—H bond to the carbonyl group proposed by Kwok and Atkinson (1995). Application of their structure-activity relations (SARs) gives 17% abstraction at this site with a channel yield of 78% for production of the acyl radical. Reaction of the acylperoxy radical with NO2 forms peroxybutanoyl nitrate, while reaction with NO forms CO2 and the -propyl radical, which then reacts with O2 to form the n-propylperoxy radical, whose main atmospheric fate is conversion to propanal. 

Darnall et al. (1976b) and Carter et al. (1979) have estimated ratios of fcb/fca of 0.04 for propylperoxy, 0.09 for butylperoxy, and 0.16 for pentylperoxy radicals. Atkinson et al. (1982a) found similar values rising up to 0.32 for n-octylperoxy radicals. In addition to these authors, Demerjian et al. (1974) and Niki et al. (1972) have shown by computer simulations of smog-chamber data that higher alkylperoxy radicals react with NO at least as rapidly as CH302. 

Several studies have been done to establish the chain-carrying species in the oxidation of alcohol (29). The absence of peroxide in the photooxidation of 2-propanol suggests either that the chain carrier is a hydroperoxy radical and not the 2-hydroxy-2-propylperoxy radical or that 2-hydroperoxy-2-propanol is too unstable to accumulate, if formed under these conditions. Only the hydroperoxy radical could be trapped by the spin-trapping reagent phenyl-N-f-butylnitrone in the oxidation of 2-propanol at 25°C (28). The reported high rate constant (30) for the decomposition of the 2-hydroxy-2-propylperoxy radical to acetone and hydroperoxy radical also implies that the hydroperoxy radical is the predominant chain carrier. On the other hand, Schenck and his co-workers (31) isolated 2-hydroperoxy-2-propanol in the photooxidation of 2-propanol with 313-nm light. 

Perhaps most pertinent to this review, model compounds play an integral role in the development of detailed chemical kinetic mechanisms. For instance, w-propylperoxy," 1-butoxy radical," and n-pentyl" radical are, respectively, the simplest alkylperoxy radical, alkoxy radical, and alkyl radical capable of undergoing facile 1,5-H atom transfers (each via a favorable six-membered-ring transition state, as illustrated in Figure 2). Thus, these smaller systems are commonly used as models to investigate the comparable isomerizations possible in the larger radical, oxy radical, and peroxy radical species that are involved in FlC fuel combustion. 

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