Chlorination of N-Phenylbenzenesulfonamides with NCP in Aqueous Acetic Acid. Using the para/meta Ratio of Substituent Effects for Mechanism Elucidation

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Title:Chlorination of N-Phenylbenzenesulfonamides with NCP in Aqueous Acetic Acid. Using the para/meta Ratio of Substituent Effects for Mechanism Elucidation
Creators:
Reis, João Carlos R.
Segurado, Manuel A. P.
Gomes de Oliveira, Jaime D.
Kabilan, Senthamaraikannan
Suganya, Krishnasamy
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 69, 12, pp. 2253-2275
Uncontrolled Keywords:Kinetics, Sulfonamides, Electrostatic interactions, Reaction mechanisms, Chlorinations, DFT calculations, Linear free energy relationships, Substituent effects

Abstract

Rate constants were measured for the oxidative chlorination reaction of <i>N</i>-phenylbenzenesulfonamide <strong>2</strong> and twelve <i>ortho</i>-, nine <i>meta</i>- and twelve <i>para</i>-substituted derivatives in the aniline moiety, using 1-chloro-3-methyl-2,6-diphenylpiperidin-4-one (<strong>1</strong>) as chlorinating agent. The kinetics was run in 50% (v/v) aqueous acetic acid acidified with perchloric acid under pseudo-first-order conditions with respect to <strong>1</strong> at five different temperatures between 298 and 318 K. The dependence of rate constants on temperature was analysed in terms of the isokinetic relationship (IKR). The resulting isokinetic temperature was estimated to be 513 K. Using the Linert's theory of the IKR, the experimental isokinetic temperature was interpreted as evidence for the preferential involvement of water molecules in the formation of activated complexes. The dependence of the rate constants on the substituents was analysed using the tetralinear extension of the Yukawa-Tsuno equation for the effects of <i>meta</i> and <i>para</i> substituents. A positively charged transition state was suggested by an experimental value <i>r</i><sup>+</sup> = 0.39 for the resonance demand, which was found to be insensitive to temperature variation. The parameter λ for the <i>para</i>/<i>meta</i> ratio of substituent effects was estimated to be 0.952. The electrostatic modelling of λ values was re-examined in the light of the recent calculations of the energies of interaction between charged and/or dipolar groups by Exner and Böhm. Based on energy ratios, the electrostatic method was shown to remain valid for the purpose of modelling λ values. The experimental λ value for the reaction indicates the formation of an activated complex possessing an electric charge in the vicinity of the nitrogen atom of the substrate. The electrophilic attack on the substrate nitrogen atom by the protonated chlorinating reagent has been proposed as the rate-determining step, with the last step being the fast rearrangement of the intermediate <i>N</i>-chloro-<i>N</i>-phenylbenzenesulfonamidium cation into the products. <p>

Title:Chlorination of N-Phenylbenzenesulfonamides with NCP in Aqueous Acetic Acid. Using the para/meta Ratio of Substituent Effects for Mechanism Elucidation
Creators:
Reis, João Carlos R.
Segurado, Manuel A. P.
Gomes de Oliveira, Jaime D.
Kabilan, Senthamaraikannan
Suganya, Krishnasamy
Uncontrolled Keywords:Kinetics, Sulfonamides, Electrostatic interactions, Reaction mechanisms, Chlorinations, DFT calculations, Linear free energy relationships, 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:69
Number:12
Page Range:pp. 2253-2275
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20042253UNSPECIFIED
ID Code:2334
Item Type:Article
Deposited On:06 Feb 2009 17:17
Last Modified:06 Feb 2009 16:17

Citation

Reis, João Carlos R.; Segurado, Manuel A. P.; Gomes de Oliveira, Jaime D.; Kabilan, Senthamaraikannan; Suganya, Krishnasamy (2004) Chlorination of N-Phenylbenzenesulfonamides with NCP in Aqueous Acetic Acid. Using the para/meta Ratio of Substituent Effects for Mechanism Elucidation. Collection of Czechoslovak Chemical Communications, 69 (12). pp. 2253-2275. ISSN 0010-0765

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