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Isomerization of n ‐hexyl and s ‐octyl radicals by 1,5 and 1,4 intramolecular hydrogen atom transfer reactions
Author(s) -
Dóbé S.,
Bérces T.,
Réti F.,
Márta F.
Publication year - 1987
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550191003
Subject(s) - chemistry , isomerization , radical , intramolecular force , hydrogen atom , disproportionation , photochemistry , radical disproportionation , medicinal chemistry , reaction rate constant , alkyl , kinetics , organic chemistry , catalysis , physics , quantum mechanics
n ‐Hexyl and s ‐octyl radical isomerizations by intramolecular hydrogen atom shift have been studied in the presence of high methyl radical concentration where isomerized alkyl radicals reacted predominantly by combination and disproportionation reactions with methyl radicals. By assuming the rate coefficient of 1‐hexyl radical recombination to be equal to that of ethyl self‐combination, the rate coefficient of log( k 1 / s −1 ) = (9.5 ± 0.3) – (11.6 ± 0.3) kcal mol −1 / RT ln 10 has been derived for the 6 sp isomerization of n ‐hexyl radicals, 1‐hexyl → 2‐hexyl (1). Investigation of s ‐octyl radical isomerization was complicated by fast interconversion between 3‐octyl, 2‐octyl, and 4‐octyl radicals. Use of the methyl trapping technique and systematic variation of methyl radical concentration made possible the determination of log( k 2 / s −1 ) = (9.4 ± 0.7) − (11.2 ± 1.0) kcal mol −1 / RT ln 10 for the 6 ss isomerization of 3‐octyl and the estimation of log( k 3 / s −1 ) = 10.5–17 kcal mol −1 / RT ln 10 for the 5 ss isomerization of 2‐octyl radicals, where 3‐octyl → 2‐octyl (2), and 2‐octyl → 4‐octyl (3).