Substituent Effects on the Base-Catalysed Hydrolysis of Phenyl Esters of para-Substituted Benzoic Acids

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Title:Substituent Effects on the Base-Catalysed Hydrolysis of Phenyl Esters of para-Substituted Benzoic Acids
Creators:
Bauerová, Ingrid
Ludwig, Miroslav
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 65, 11, pp. 1777-1790
Uncontrolled Keywords:Chemometrics, Kinetic acidity function, AISE, Kinetics, Esters, Base-catalysed hydrolysis, Phenyl benzoates, Hammett equation, Substituent effects

Abstract

Seventeen model phenyl esters of 4-substituted benzoic acids were synthesised by the reaction of substituted benzoyl chlorides with phenol in aqueous alkaline solutions (Schotten-Baumann reaction), in pyridine (Einhorn reaction), or by the reaction of substituted benzoic acids with phosphorus oxychloride. Structures and purity of the model compounds were confirmed by <sup>1</sup>H NMR and <sup>13</sup>C NMR spectroscopy as well as by HPLC and elemental analysis. Phenyl 4-aminobenzoate was synthesised by reduction of phenyl 4-nitrobenzoate in methanol on palladium. Kinetics of base-catalysed hydrolysis of model phenyl esters occurring by the B<sub>Ac</sub>2 mechanism were measured by UV spectrophotometry in 50% (v/v) aqueous dimethyl sulfoxide solutions at 25 °C under pseudo-first-order conditions, (<i>c</i>[NaOH] = 0.001-1.0 mol l<sup>-1</sup>). The addition of OH<sup>-</sup> to phenyl benzoates was used to establish the kinetic <i>J</i><sub>-</sub><sup>E</sup> acidity scale. Linear relation between <i>J</i><sub>-</sub><sup>E</sup> and log <i>k</i><sub>obs</sub> with the slope near unity was found for all the model compounds. The kinetic constants of hydrolysis of phenyl esters of 4-substituted benzoic acids precisely obey the Hammett relationship (σ<sub>p</sub>) with ρ = 2.44. Quantitatively comparable results have been obtained by application of Alternative Interpretation of Substituent Effects theory (AISE) using the σ<sup>i</sup> set of substituent constants. <p>

Title:Substituent Effects on the Base-Catalysed Hydrolysis of Phenyl Esters of para-Substituted Benzoic Acids
Creators:
Bauerová, Ingrid
Ludwig, Miroslav
Uncontrolled Keywords:Chemometrics, Kinetic acidity function, AISE, Kinetics, Esters, Base-catalysed hydrolysis, Phenyl benzoates, Hammett equation, 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:65
Number:11
Page Range:pp. 1777-1790
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20001777UNSPECIFIED
ID Code:1758
Item Type:Article
Deposited On:06 Feb 2009 17:12
Last Modified:06 Feb 2009 16:12

Citation

Bauerová, Ingrid; Ludwig, Miroslav (2000) Substituent Effects on the Base-Catalysed Hydrolysis of Phenyl Esters of para-Substituted Benzoic Acids. Collection of Czechoslovak Chemical Communications, 65 (11). pp. 1777-1790. ISSN 0010-0765

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