Reactions of Carbonyl Compounds in Basic Solutions. Part 34. The Mechanism of the Base-Catalysed Ring Fission of 2,3-Diphenylcycloprop-2-en-1-one

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Title:Reactions of Carbonyl Compounds in Basic Solutions. Part 34. The Mechanism of the Base-Catalysed Ring Fission of 2,3-Diphenylcycloprop-2-en-1-one
Creators:
Bowden, Keith
Burgess, Emma J.
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 64, 10, pp. 1594-1600
Uncontrolled Keywords:Reaction kinetics, Cyclopropenones, Ring fission, Ketones, Substituent effects

Abstract

The rate coefficients for the base-catalysed ring fission of a series of 2-phenyl-3-(2-, 3- or 4-substituted phenyl)cycloprop-2-en-1-ones to give the corresponding (<i>E</i>)-2,3-diphenylacrylic acids have been determined in water at 30.0 °C, as well as for the unsubstituted compound at 40.0, 50.0 and 60.0&nbsp;°C. The effects of <i>meta</i>- and <i>para</i>-substituents on the rates have been correlated using the Hammett equation to give a reaction constant, ρ, equal to <i>ca</i> 1.2 at 30&nbsp;°C. For the unsubstituted compound, the activation parameters have been calculated and the kinetic solvent isotope effect has been studied. The effects of <i>ortho</i>-substituents on the rates appear to be mainly polar, rather than steric, in origin. The evidence indicates a mechanistic pathway which proceeds by addition of hydroxide anion to the ketone, which is rate-determining. The adduct suffers ring fission to give the final product <i>via</i> a carbanionic intermediate. <p>

Title:Reactions of Carbonyl Compounds in Basic Solutions. Part 34. The Mechanism of the Base-Catalysed Ring Fission of 2,3-Diphenylcycloprop-2-en-1-one
Creators:
Bowden, Keith
Burgess, Emma J.
Uncontrolled Keywords:Reaction kinetics, Cyclopropenones, Ring fission, Ketones, Substituent effects
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:64
Number:10
Page Range:pp. 1594-1600
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19991594UNSPECIFIED
ID Code:1581
Item Type:Article
Deposited On:06 Feb 2009 17:10
Last Modified:06 Feb 2009 16:10

Citation

Bowden, Keith; Burgess, Emma J. (1999) Reactions of Carbonyl Compounds in Basic Solutions. Part 34. The Mechanism of the Base-Catalysed Ring Fission of 2,3-Diphenylcycloprop-2-en-1-one. Collection of Czechoslovak Chemical Communications, 64 (10). pp. 1594-1600. ISSN 0010-0765

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