Studies of the Formation and Stability of Pentadienyl and 3-Substituted Pentadienyl Radicals

K. Brady Clark; David Griller; Peter N. Culshaw; John C. Walton; F. P. Lossing; J. A.Martinho Simôes

doi:10.1021/jo00019a012

Studies of the Formation and Stability of Pentadienyl and 3-Substituted Pentadienyl Radicals

K. Brady Clark^*, David Griller, Peter N. Culshaw, John C. Walton, F. P. Lossing, J. A.Martinho Simôes

^*Corresponding author for this work

School of Chemistry

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Abstract

Pentadienyl radicals and their 3-methyl and 3-hydroxy derivatives were generated from the corresponding 1, 4-pentadienes. The rates of hydrogen abstraction were studied by laser flash photolysis, and the bisallylic C-H bond dissociation energies were determined by photoacoustic calorimetry. Pentadienyl radicals were also generated by monoenergetic electron bombardment of 3-tert-butyl-1,4-pentadiene, and the radical’s enthalpy of formation was deduced from the appearance energy of the tert-butyl cation. Evaluation of all recent data leads to recommended values of [formula omitted] (pentadienyl) = 49.8 ± 1.0 kcal mol⁻¹ and DH°((CH₂=CH)₂CH) = 76.6 ± 1.0 kcal mol⁻¹. The EPR spectra of 3-methylpentadienyl and several other radicals were also examined. The effect of substituents on the stabilization energy of pentadienyl radicals was assessed, and pentadienyl radicals were compared with other delocalized polyenyl radicals.

Original language	English
Pages (from-to)	5535-5539
Number of pages	5
Journal	The Journal of Organic Chemistry
Volume	56
Issue number	19
DOIs	https://doi.org/10.1021/jo00019a012
Publication status	Published - 1 Sept 1991

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title = "Studies of the Formation and Stability of Pentadienyl and 3-Substituted Pentadienyl Radicals",

abstract = "Pentadienyl radicals and their 3-methyl and 3-hydroxy derivatives were generated from the corresponding 1, 4-pentadienes. The rates of hydrogen abstraction were studied by laser flash photolysis, and the bisallylic C-H bond dissociation energies were determined by photoacoustic calorimetry. Pentadienyl radicals were also generated by monoenergetic electron bombardment of 3-tert-butyl-1,4-pentadiene, and the radical{\textquoteright}s enthalpy of formation was deduced from the appearance energy of the tert-butyl cation. Evaluation of all recent data leads to recommended values of [formula omitted] (pentadienyl) = 49.8 ± 1.0 kcal mol−1 and DH°((CH2=CH)2CH) = 76.6 ± 1.0 kcal mol−1. The EPR spectra of 3-methylpentadienyl and several other radicals were also examined. The effect of substituents on the stabilization energy of pentadienyl radicals was assessed, and pentadienyl radicals were compared with other delocalized polyenyl radicals.",

author = "Clark, {K. Brady} and David Griller and Culshaw, {Peter N.} and Walton, {John C.} and Lossing, {F. P.} and Sim{\^o}es, {J. A.Martinho}",

year = "1991",

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doi = "10.1021/jo00019a012",

language = "English",

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T1 - Studies of the Formation and Stability of Pentadienyl and 3-Substituted Pentadienyl Radicals

AU - Clark, K. Brady

AU - Griller, David

AU - Culshaw, Peter N.

AU - Walton, John C.

AU - Lossing, F. P.

AU - Simôes, J. A.Martinho

PY - 1991/9/1

Y1 - 1991/9/1

N2 - Pentadienyl radicals and their 3-methyl and 3-hydroxy derivatives were generated from the corresponding 1, 4-pentadienes. The rates of hydrogen abstraction were studied by laser flash photolysis, and the bisallylic C-H bond dissociation energies were determined by photoacoustic calorimetry. Pentadienyl radicals were also generated by monoenergetic electron bombardment of 3-tert-butyl-1,4-pentadiene, and the radical’s enthalpy of formation was deduced from the appearance energy of the tert-butyl cation. Evaluation of all recent data leads to recommended values of [formula omitted] (pentadienyl) = 49.8 ± 1.0 kcal mol−1 and DH°((CH2=CH)2CH) = 76.6 ± 1.0 kcal mol−1. The EPR spectra of 3-methylpentadienyl and several other radicals were also examined. The effect of substituents on the stabilization energy of pentadienyl radicals was assessed, and pentadienyl radicals were compared with other delocalized polyenyl radicals.

AB - Pentadienyl radicals and their 3-methyl and 3-hydroxy derivatives were generated from the corresponding 1, 4-pentadienes. The rates of hydrogen abstraction were studied by laser flash photolysis, and the bisallylic C-H bond dissociation energies were determined by photoacoustic calorimetry. Pentadienyl radicals were also generated by monoenergetic electron bombardment of 3-tert-butyl-1,4-pentadiene, and the radical’s enthalpy of formation was deduced from the appearance energy of the tert-butyl cation. Evaluation of all recent data leads to recommended values of [formula omitted] (pentadienyl) = 49.8 ± 1.0 kcal mol−1 and DH°((CH2=CH)2CH) = 76.6 ± 1.0 kcal mol−1. The EPR spectra of 3-methylpentadienyl and several other radicals were also examined. The effect of substituents on the stabilization energy of pentadienyl radicals was assessed, and pentadienyl radicals were compared with other delocalized polyenyl radicals.

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DO - 10.1021/jo00019a012

M3 - Article

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SN - 0022-3263

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EP - 5539

JO - The Journal of Organic Chemistry

JF - The Journal of Organic Chemistry

IS - 19

ER -

Studies of the Formation and Stability of Pentadienyl and 3-Substituted Pentadienyl Radicals

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