Comprehensive Oxidation Mechanism of n‑Butylamine and 2‑Butylamine by H and OH Radicals: Insights into Reactivity

TL;DR

This paper investigates how H and OH radicals react with butylamines, revealing how the amino group's position affects reaction rates and outcomes.

Contribution

The study provides new theoretical insights into the oxidation mechanisms of butylamines by H and OH radicals, including multistructural and torsional effects.

Findings

The position of the amino group influences reaction barrier heights and kinetics.

H-abstraction by H radicals is most favorable at the α-site.

OH radicals prefer N-site abstraction due to torsional anharmonicity effects.

Abstract

This study presents
the accurate thermal rate constants for a series
of hydrogen abstraction reactions involving 1- and 2-butylamine and
key radicals H and OH. The potential energy surface resulting from
these reactions was examined by using the M08-HX/ma-TZVP level of
theory. The rate coefficients were calculated within the multistructural
canonical variational theory with small-curvature tunneling correction
(MS-CVT/SCT). Multistructural effects and the torsional anharmonicity
corrections were evaluated through the rovibrational partition function
calculated with the multistructural method based on a coupled torsional
potential (MS-T). Our results demonstrated an influence of the position
of the amino functional group on the kinetics. The gradual decrease
in barrier heights was observed with increasing distance between the
amino functional group and the reaction site. The calculated branching
ratios demonstrated that the H-abstraction by the H radicals at the
α-site is favored. In reactions involving OH radicals, the channel
at the N-site shows a greater proportion due to its increased multistructural
torsional anharmonicity and a reduced variational effect of other
sites.

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