Formation of alkyl nitrates from the reaction of branched and cyclic alkyl peroxy radicals with NO

Abstract The yields of C 5 and C 6 alkyl nitrates from neopentane, 2‐methylbutane, 2‐methylpentane, 3‐methylpentane, and cyclohexane have been measured in irradiated CH 3 ONONO‐alkane‐air mixtures at 298 ± 2 K and 735‐torr total pressure. Additionally, OH radical rate constants for neopentyl nitrate, 3‐nitro‐2‐methylbutane, 2‐nitro‐2‐methylpentane, 2‐nitro‐3‐methylpentane, and cyclohexyl nitrate, relative to that for n ‐butane, have been determined at 298 ± 2 K. Using a rate constant for the reaction of OH radicals with n ‐butane of 2.58 × 10 −12 cm 3 molecule −1 s −1 , these OH radical rate constants are (in units of 10 −12 cm 3 molecule −1 s −1 ): neopentyl nitrate, 0.87 ± 0.21; cyclohexyl nitrate, 3.35 ± 0.36; 3‐nitro‐2‐methylbutane, 1.75 ± 0.06; 2‐nitro‐2‐methylpentane, 1.75 ± 0.22; and 2‐nitro‐3‐methylpentane, 3.07 ± 0.08. After accounting for consumption of the alkyl nitrates by OH radical reaction and for the yields of the individual alkyl peroxy radicals formed in the reaction of OH radicals with the alkanes studied, the alkyl nitrate yields (which reflect the fraction of the individual RO 2 radicals reacting with NO to form RONO 2 ) determined were: neopentyl nitrate, 0.0513 ± 0.0053; cyclohexyl nitrate, 0.160 ± 0.015; 3‐nitro‐2‐methylbutane, 0.109 ± 0.003; 2‐nitro‐2methylbutane, 0.0533 ± 0.0022; 2‐nitro‐2‐methylpentane, 0.0350 ± 0.0096; 3‐ + 4‐nitro‐2‐methylpentane, 0.165 ± 0.016; and 2‐nitro‐3‐methylpentane, 0.140 ± 0.014. These results are discussed and compared with previous literature values for the alkyl nitrates formed from primary and secondary alkyl peroxy radicals generated from a series of n ‐alkanes.