posted on 2014-05-01, 00:00authored byVictor
B. Oyeyemi, John A. Keith, Emily A. Carter
As part of our ongoing investigation
of the combustion chemistry
of oxygenated molecules using multireference correlated wave function
methods, we report bond dissociation energies (BDEs) in C1–C4
alcohols (from methanol to the four isomers of butanol) and C1–C4
aldehydes (from methanal to butanal). The BDEs are calculated with
a multireference averaged coupled-pair functional-based scheme. We
compare these multireference BDEs with those derived from experiment
and single-reference methods. Trends in BDEs for the alcohols and
aldehydes are rationalized by considering geometry relaxations of
dissociated radical fragments, resonance stabilization, and hyperconjugation.
Lastly, we discuss the conjectured association between bond strengths
and rates of hydrogen abstraction by hydroxyl radicals. In general,
abstraction reaction rates are higher at sites where the C–H
bond energies are lower (and vice versa). However, comparison with
available rate data shows this inverse relationship between bond strengths
and abstraction rates does not hold at all temperatures.