A curve-crossing model for oxidative decarboxylation. Kinetics of anilino carboxylate fragmentations

Ian Gould, Jerome R. Lenhard, Samir Farid

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The kinetics of oxidative decarboxylation of a series of anilino carboxylates have been measured. These compounds find use in the recently described two-electron sensitization process for silver halide photography, and control of their fragmentation kinetics is essential to be useful in this application. The measured rate constants vary over 5 orders of magnitude. The decarboxylation rate constants decrease substantially with increasing solvent polarity, an effect that results in misleading Arrhenius analysis of temperature effect measurements. The rate constants also depend on the product radical stability and the oxidation potential of the aniline precursor. A valence bond curve-crossing model is proposed that provides a combined picture of this and the related decarboxylation of acyloxy radicals. The model is able to explain the substitution and solvent polarity effects. Consistent with this model, manipulation of solvation via changes in substituants (hydrophilic vs hydrophobic) around the reaction site is shown to strongly influence the decarboxylation rate constants. In this way, the decarboxylation rate constants can be altered by nearly 3 orders of magnitude at constant solvent polarity and precursor oxidation potential.

Original languageEnglish (US)
Pages (from-to)10949-10956
Number of pages8
JournalJournal of Physical Chemistry A
Volume108
Issue number50
DOIs
StatePublished - Dec 16 2004

Fingerprint

decarboxylation
carboxylates
Rate constants
fragmentation
Kinetics
kinetics
curves
polarity
Silver halides
Oxidation
Solvation
Photography
oxidation
silver halides
Thermal effects
photography
aniline
Substitution reactions
solvation
temperature effects

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

A curve-crossing model for oxidative decarboxylation. Kinetics of anilino carboxylate fragmentations. / Gould, Ian; Lenhard, Jerome R.; Farid, Samir.

In: Journal of Physical Chemistry A, Vol. 108, No. 50, 16.12.2004, p. 10949-10956.

Research output: Contribution to journalArticle

@article{5636cfc744bc4983b88988d65df9a49c,
title = "A curve-crossing model for oxidative decarboxylation. Kinetics of anilino carboxylate fragmentations",
abstract = "The kinetics of oxidative decarboxylation of a series of anilino carboxylates have been measured. These compounds find use in the recently described two-electron sensitization process for silver halide photography, and control of their fragmentation kinetics is essential to be useful in this application. The measured rate constants vary over 5 orders of magnitude. The decarboxylation rate constants decrease substantially with increasing solvent polarity, an effect that results in misleading Arrhenius analysis of temperature effect measurements. The rate constants also depend on the product radical stability and the oxidation potential of the aniline precursor. A valence bond curve-crossing model is proposed that provides a combined picture of this and the related decarboxylation of acyloxy radicals. The model is able to explain the substitution and solvent polarity effects. Consistent with this model, manipulation of solvation via changes in substituants (hydrophilic vs hydrophobic) around the reaction site is shown to strongly influence the decarboxylation rate constants. In this way, the decarboxylation rate constants can be altered by nearly 3 orders of magnitude at constant solvent polarity and precursor oxidation potential.",
author = "Ian Gould and Lenhard, {Jerome R.} and Samir Farid",
year = "2004",
month = "12",
day = "16",
doi = "10.1021/jp040536x",
language = "English (US)",
volume = "108",
pages = "10949--10956",
journal = "Journal of Physical Chemistry A",
issn = "1089-5639",
publisher = "American Chemical Society",
number = "50",

}

TY - JOUR

T1 - A curve-crossing model for oxidative decarboxylation. Kinetics of anilino carboxylate fragmentations

AU - Gould, Ian

AU - Lenhard, Jerome R.

AU - Farid, Samir

PY - 2004/12/16

Y1 - 2004/12/16

N2 - The kinetics of oxidative decarboxylation of a series of anilino carboxylates have been measured. These compounds find use in the recently described two-electron sensitization process for silver halide photography, and control of their fragmentation kinetics is essential to be useful in this application. The measured rate constants vary over 5 orders of magnitude. The decarboxylation rate constants decrease substantially with increasing solvent polarity, an effect that results in misleading Arrhenius analysis of temperature effect measurements. The rate constants also depend on the product radical stability and the oxidation potential of the aniline precursor. A valence bond curve-crossing model is proposed that provides a combined picture of this and the related decarboxylation of acyloxy radicals. The model is able to explain the substitution and solvent polarity effects. Consistent with this model, manipulation of solvation via changes in substituants (hydrophilic vs hydrophobic) around the reaction site is shown to strongly influence the decarboxylation rate constants. In this way, the decarboxylation rate constants can be altered by nearly 3 orders of magnitude at constant solvent polarity and precursor oxidation potential.

AB - The kinetics of oxidative decarboxylation of a series of anilino carboxylates have been measured. These compounds find use in the recently described two-electron sensitization process for silver halide photography, and control of their fragmentation kinetics is essential to be useful in this application. The measured rate constants vary over 5 orders of magnitude. The decarboxylation rate constants decrease substantially with increasing solvent polarity, an effect that results in misleading Arrhenius analysis of temperature effect measurements. The rate constants also depend on the product radical stability and the oxidation potential of the aniline precursor. A valence bond curve-crossing model is proposed that provides a combined picture of this and the related decarboxylation of acyloxy radicals. The model is able to explain the substitution and solvent polarity effects. Consistent with this model, manipulation of solvation via changes in substituants (hydrophilic vs hydrophobic) around the reaction site is shown to strongly influence the decarboxylation rate constants. In this way, the decarboxylation rate constants can be altered by nearly 3 orders of magnitude at constant solvent polarity and precursor oxidation potential.

UR - http://www.scopus.com/inward/record.url?scp=10944225928&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=10944225928&partnerID=8YFLogxK

U2 - 10.1021/jp040536x

DO - 10.1021/jp040536x

M3 - Article

VL - 108

SP - 10949

EP - 10956

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 50

ER -