Atmospheric degradation of saturated alcohols: Room temperature rate coefficients for NO3 radical reactions

Rate coefficients for the reactions of NO3 radicals with a series of saturated alcohols are reported here using the relative rate technique. Experiments were performed using air as bath gas in a 50 L glass-pyrex reaction chamber at room temperature (298 ± 2) K with long-path FTIR spectroscopy used to monitor the reaction at atmospheric pressure (708 ± 8) Torr. The reference compounds used and their rate coefficients are: propanal kNO3 = (6.0 ± 0.6) × 10−15, methyl methacrylate kNO3 = (3.55 ± 0.62) × 10−15, acetaldehyde kNO3 = (2.62 ± 0.29) × 10−15 and propene kNO3 = (9.50 ± 1.9) × 10−15, in cm3 molecule−1 s−1. Rate coefficients obtained were (in units cm3 molecule−1 s−1): (1.87 ± 0.14) × 10−15, (2.39 ± 0.20) × 10−15, (2.28 ± 0.17) × 10−15, (1.80 ± 0.13) × 10−15 and (3.52 ± 0.19) × 10−15 for 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3,3-dimethyl-1-butanol and 3,3-dimethyl-2-butanol respectively. Reactivity trend can be explained in terms of the different types of hydrogen inside the hydrocarbon chain. The reaction occurs by an initial H-atom abstraction mainly from C-H groups of the alcohols by the NO3 radical being NO3 more reactive towards an H atom attached to a tertiary carbon than that attached to a secondary or primary carbon. Reactivity trend is compared with their similar structural 2-butanol and with the corresponding alkanes. Atmospheric implications are also discussed calculating lifetimes of the saturated alcohols studied here due to the reaction with NO3 radicals in comparison to their reactions with the other major atmospheric oxidants.