Open AccessCompetition H(D) Kinetic Isotope Effects in the Autoxidation of Hydrocarbons
Author(s) -
Hubert Muchalski,
Alexander J. Levonyak,
Libin Xu,
K. U. Ingold,
Ned A. Porter
Publication year - 2014
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/ja511434j
Subject(s) - chemistry , autoxidation , kinetic isotope effect , intramolecular force , deuterium , hydrogen atom abstraction , tetralin , hydrogen atom , photochemistry , computational chemistry , hydrogen , stereochemistry , organic chemistry , atomic physics , alkyl , catalysis , physics
Hydrogen atom transfer is central to many important radical chain sequences. We report here a method for determination of both the primary and secondary isotope effects for symmetrical substrates by the use of NMR. Intramolecular competition reactions were carried out on substrates having an increasing number of deuterium atoms at symmetry-related sites. Products that arise from peroxyl radical abstraction at each position of the various substrates reflect the competition rates for H(D) abstraction. The primary KIE for autoxidation of tetralin was determined to be 15.9 ± 1.4, a value that exceeds the maximum predicted by differences in H(D) zero-point energies (∼7) and strongly suggests that H atom abstraction by the peroxyl radical occurs with substantial quantum mechanical tunneling.