Why are sec-alkylperoxyl bimolecular self-reactions orders of magnitude faster than the analogous reactions of tert-alkylperoxyls? The unanticipated role of CH hydrogen bond donation
Date
2016
Authors
Lee, Richmond
Gryn'ova, Ganna
Ingold, K. U.
Coote, Michelle
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Royal Society of Chemistry
Abstract
High-level ab initio calculations are used to identify the mechanism of secondary (and primary)
alkylperoxyl radical termination and explain why their reactions are much faster than their tertiary
counterparts. Contrary to existing literature, the decomposition of both tertiary and non-tertiary
tetroxides follows the same asymmetric two-step bond cleavage pathway to form a caged intermediate
of overall singlet multiplicity comprising triplet oxygen and two alkoxyl radicals. The alpha hydrogen
atoms of non-tertiary species facilitate this process by forming unexpected CHO hydrogen bonds to
the evolving O2. For non-tertiary peroxyls, subsequent alpha hydrogen atom transfer then yields the
experimentally observed non-radical products, ketone, alcohol and O2, whereas for tertiary species, this
reaction is precluded and cage escape of the (unpaired) alkoxyl radicals is a likely outcome with
important consequences for autoxidation.
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Physical Chemistry Chemical Physics
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Journal article
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