Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates

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Title:Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates
Creators:
Nummert, Vilve
Piirsalu, Mare
Koppel, Ilmar A.
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 71, 11-12, pp. 1557-1570
Uncontrolled Keywords:Kinetics, Esters, Alkaline hydrolysis, Alkyl benzoates, Solvent effects, Substituent effects

Abstract

The second-order rate constants <i>k</i><sub>2</sub> (dm<sup>3</sup> mol<sup>-1</sup> s<sup>-1</sup>) for the alkaline hydrolysis of substituted alkyl benzoates C<sub>6</sub>H<sub>5</sub>CO<sub>2</sub>R have been measured spectrophotometrically in aqueous 0.5 M Bu<sub>4</sub>NBr at 50 and 25 °C (R = CH<sub>3</sub>, CH<sub>2</sub>Cl, CH<sub>2</sub>CN, CH<sub>2</sub>C≡CH, CH<sub>2</sub>C<sub>6</sub>H<sub>5</sub>, CH<sub>2</sub>CH<sub>2</sub>Cl, CH<sub>2</sub>CH<sub>2</sub>OCH<sub>3</sub>, CH<sub>2</sub>CH<sub>3</sub>) and in aqueous 5.3 M NaClO<sub>4</sub> at 25 °C (R = CH<sub>3</sub>, CH<sub>2</sub>Cl, CH<sub>2</sub>CN, CH<sub>2</sub>C≡CH). The dependence of the alkyl substituent effects on different solvent parameters was studied using the following equations: <br />&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;∆ log <i>k</i> = <i>c</i><sub>0</sub> + <i>c</i><sub>1</sub>σ<sub>I</sub> + <i>c</i><sub>2</sub><i>E</i><sub>s</sub><sup>B</sup> + <i>c</i><sub>3</sub>∆<i>E</i> + <i>c</i><sub>4</sub>∆<i>Y</i> + <i>c</i><sub>5</sub>∆<i>P</i> + <i>c</i><sub>6</sub>∆<i>E</i>σ<sub>I</sub> + <i>c</i><sub>7</sub>∆<i>Y</i>σ<sub>I</sub> + <i>c</i><sub>8</sub>∆<i>P</i>σ<sub>I</sub> <br />&nbsp;&nbsp;&nbsp;&nbsp;∆ log <i>k</i> = <i>c</i><sub>0</sub> + <i>c</i><sub>1</sub>σ* +<sub> </sub><i>c</i><sub>2</sub><i>E</i><sub>s</sub><sup>B</sup> + <i>c</i><sub>3</sub>∆<i>E</i> + <i>c</i><sub>4</sub>∆<i>Y</i> + <i>c</i><sub>5</sub>∆<i>P</i> + <i>c</i><sub>6</sub>∆<i>E</i>σ* + <i>c</i><sub>7</sub>∆<i>Y</i>σ* + <i>c</i><sub>8</sub>∆<i>P</i>σ*&nbsp;. <br />&nbsp;<br />∆ log <i>k</i> = log <i>k</i><sup>R</sup> - log <i>k</i><sup>CH3</sup>. σ<sub>I</sub> and σ* are the Taft inductive and polar substituent constants. <i>E</i>, <i>Y</i> and <i>P</i> are the solvent electrophilicity, polarity and polarizability parameters, respectively. In the data treatment ∆<i>E</i> = <i>E</i><sub>S</sub> - <i>E</i><sub>H2O</sub>&nbsp;, ∆<i>Y</i> = <i>Y</i><sub>S</sub> - <i>Y</i><sub>H2O</sub>&nbsp;, ∆<i>P</i> = <i>P</i><sub>S</sub> - <i>P</i><sub>H2O</sub> were used. The solvent electrophilicity, <i>E</i>, was found to be the main factor responsible for changes in alkyl substituent effects with medium. When σ<sub>I</sub> constants were used, variation of the polar term of alkyl substituents with the solvent electrophilicity <i>E</i> was found to be similar to that observed earlier for <i>meta</i> and <i>para</i> substituents, but twice less when σ* constants were used. The steric term for alkyl substituents was approximately independent of the solvent parameters. <p>

Title:Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates
Creators:
Nummert, Vilve
Piirsalu, Mare
Koppel, Ilmar A.
Uncontrolled Keywords:Kinetics, Esters, Alkaline hydrolysis, Alkyl benzoates, Solvent effects, 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:71
Number:11-12
Page Range:pp. 1557-1570
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20061557UNSPECIFIED
ID Code:2562
Item Type:Article
Deposited On:06 Feb 2009 17:19
Last Modified:06 Feb 2009 16:19

Citation

Nummert, Vilve; Piirsalu, Mare; Koppel, Ilmar A. (2006) Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates. Collection of Czechoslovak Chemical Communications, 71 (11-12). pp. 1557-1570. ISSN 0010-0765

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