Kinetic Study of Alkaline Hydrolysis of Substituted Phenyl Tosylates. XXII. Variation of Ortho Substituent Effect with Solvent

[img]PDF - Authorized users only
Language: English
169Kb
Title:Kinetic Study of Alkaline Hydrolysis of Substituted Phenyl Tosylates. XXII. Variation of Ortho Substituent Effect with Solvent
Creators:
Nummert, Vilve
Piirsalu, Mare
Lepp, Marika
Mäemets, Vahur
Koppel, Ilmar
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 70, 2, pp. 198-222
Uncontrolled Keywords:Phenyl tosylates, Kinetics, Esters, Alkaline hydrolysis, Solvent effects, Sulfonates, Ortho effects, Substituent effects

Abstract

The second-order rate constants <i>k</i> (dm<sup>3</sup> mol<sup>-1</sup> s<sup>-1</sup>) for the alkaline hydrolysis of <i>meta</i>-, <i>para</i>-, and <i>ortho</i>-substituted phenyl tosylates 4-CH<sub>3</sub>C<sub>6</sub>H<sub>4</sub>SO<sub>2</sub>OC<sub>6</sub>H<sub>4</sub>-X in aqueous 0.5 M Bu<sub>4</sub>NBr have been measured spectrophotometrically in a wide temperature range. The log <i>k</i> values for <i>ortho</i>-substituted derivatives at various temperatures together with <i>meta</i>- and <i>para</i>-substituted derivatives were analyzed using the modified Fujita-Nishioka equation log <i>k</i><sub>m,p,ortho</sub>&nbsp;= <i>c</i><sub>0</sub> + <i>c</i><sub>1(m,p,ortho)</sub>σ° + <i>c</i><sub>2(ortho)</sub>σ<sub>I</sub> + <i>c</i><sub>3</sub>(1/<i>T</i>) + <i>c</i><sub>4(m,p,ortho)</sub>(1/<i>T</i>)σ° + <i>c</i><sub>5(ortho)</sub>(1/<i>T</i>)σ<sub>I</sub>. In order to study the dependence of substituent effects, especially ortho inductive and resonance terms on different solvent parameters, the following equation was used: ∆log <i>k</i><sub>m,p,ortho</sub> = <i>c</i><sub>0</sub> + <i>c</i><sub>1(m,p,ortho)</sub>σ° + <i>c</i><sub>2(ortho)</sub>σ<sub>I</sub> + <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(m,p,ortho)</sub>∆<i>E</i>σ° + + <i>c</i><sub>7(m,p,ortho)</sub>∆<i>Y</i>σ° + <i>c</i><sub>8(m,p,ortho)</sub>∆<i>P</i>σ° + <i>c</i><sub>9(ortho)</sub>∆<i>E</i>σ<sub>I</sub> + <i>c</i><sub>10(ortho)</sub>∆<i>Y</i>σ<sub>I</sub> + <i>c</i><sub>11(ortho)</sub>∆<i>P</i>σ<sub>I</sub>. ∆log <i>k</i> = log <i>k</i><sup>X</sup> - log <i>k</i><sup>H</sup>, σ° and σ<sub>I</sub>, are the Taft polar and inductive substituent constants, <i>E</i>, <i>Y</i> and <i>P</i>, are the solvent electrophilicity, polarity and polarizability parameters, respectively. In data treatment ∆<i>E</i> = <i>E</i><sub>S</sub> - <i>E</i><sub>H2O</sub>, ∆<i>Y</i> = <i>Y</i><sub>S</sub> - <i>Y</i><sub>H2O</sub>, ∆<i>P</i> = <i>P</i><sub>S</sub> - <i>P</i><sub>H2O</sub> were used. The solvent electrophilicity was found to be the main factor responsible for changes in the ortho, para, and meta polar substituent effects with medium. The variation of the ortho inductive term with the solvent electrophilicity <i>E</i><sub>S</sub> was found to be twice smaller than that for para substituents, while the ortho resonance term appeared to vary with solvent nearly similarly to that for para substituents. The ortho effect caused by the supplementary inductive effect from ortho position was found to disappear in a solvent whose electrophilic solvating power is comparable to pure DMSO (<i>E</i> ≈ 4). <p>

Title:Kinetic Study of Alkaline Hydrolysis of Substituted Phenyl Tosylates. XXII. Variation of Ortho Substituent Effect with Solvent
Creators:
Nummert, Vilve
Piirsalu, Mare
Lepp, Marika
Mäemets, Vahur
Koppel, Ilmar
Uncontrolled Keywords:Phenyl tosylates, Kinetics, Esters, Alkaline hydrolysis, Solvent effects, Sulfonates, Ortho 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:70
Number:2
Page Range:pp. 198-222
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20050198UNSPECIFIED
ID Code:2353
Item Type:Article
Deposited On:06 Feb 2009 17:17
Last Modified:06 Feb 2009 16:18

Citation

Nummert, Vilve; Piirsalu, Mare; Lepp, Marika; Mäemets, Vahur; Koppel, Ilmar (2005) Kinetic Study of Alkaline Hydrolysis of Substituted Phenyl Tosylates. XXII. Variation of Ortho Substituent Effect with Solvent. Collection of Czechoslovak Chemical Communications, 70 (2). pp. 198-222. ISSN 0010-0765

Repository Staff Only: item control page