Kinetics of the reactions of OH radicals with n-butyl, isobutyl, n-pentyl and 3-methyl-1-butyl nitrates

Publication date: April 2017
Source:Atmospheric Environment, Volume 155
Author(s): Yuri Bedjanian, Julien Morin, Manolis N. Romanias
The kinetics of the reactions of n-butyl (BTN), isobutyl (IBN), n-pentyl (PTN) and 3-methyl-1-butyl (3M1BN) nitrates with OH radicals has been studied using a low pressure flow tube reactor combined with a quadrupole mass spectrometer. The rate constants of the title reactions were determined under pseudo-first order conditions from kinetics of OH consumption in high excess of the nitrates. The overall rate coefficients, kBTN = 1.0 × 10⁻¹³ (T/298)^3.36 exp(838/T) (T = 288–500 K), kIBN = 2.8 × 10⁻¹⁴ (T/298)^4.09 exp(1127/T) (T = 283–500 K), kPTN = 1.26 × 10⁻¹² (T/298)^4.56 exp(45/T) (T = 298–496 K) and k3M1BN = 8.47×10⁻¹⁴ (T/298)^3.52 exp(1069/T) cm³molecule⁻¹s⁻¹ (T = 288–538 K) (with conservative 15% uncertainty), were determined at a total pressure of 1 Torr of helium. The yields of the carbonyl compounds, n-butanal (n-C3H7CHO) and isobutanal ((CH3)2CHCHO), resulting from the abstraction by OH of an α-hydrogen atom in n-butyl and isobutyl nitrates, followed by α-substituted alkyl radical decomposition, were determined at T = 300 K to be 0.10 ± 0.02 and 0.15 ± 0.03, respectively. The calculated tropospheric lifetimes of BTN, IBN, PTN and 3M1BN indicate that reaction of these nitrates with OH represents an important sink of these compounds in the atmosphere.



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