Atmospheric Chemistry of i-Butanol

Smog chamber/FTIR techniques were used to determine rate constants of k(Cl + i-butanol) = (2.06 ± 0.40) × 10−10, k(Cl + i-butyraldehyde) = (1.37 ± 0.08) × 10−10, and k(OH + i-butanol) = (1.14 ± 0.17) × 10−11 cm3 molecule−1 s−1 in 700 Torr of N2/O2 diluent at 296 ± 2K. The UV irradiation of i-butanol/Cl2/N2 mixtures gave i-butyraldehyde in a molar yield of 53 ± 3%. The chlorine atom initiated oxidation of i-butanol in the absence of NO gave i-butyraldehyde in a molar yield of 48 ± 3%. The chlorine atom initiated oxidation of i-butanol in the presence of NO gave (molar yields): i-butyraldehyde (46 ± 3%), acetone (35 ± 3%), and formaldehyde (49 ± 3%). The OH radical initiated oxidation of i-butanol in the presence of NO gave acetone in a yield of 61 ± 4%. The reaction of chlorine atoms with i-butanol proceeds 51 ± 5% via attack on the α-position to give an α-hydroxy alkyl radical that reacts with O2 to give i-butyraldehyde. The atmospheric fate of (CH3)2C(O)CH2OH alkoxy radicals is decomposition to acetone and CH2OH radicals. The atmospheric fate of OCH2(CH3)CHCH2OH alkoxy radicals is decomposition to formaldehyde and CH3CHCH2OH radicals. The results are consistent with, and serve to validate, the mechanism that has been assumed in the estimation of the photochemical ozone creation potential of i-butanol.