<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><p>For mono-substituted anilines, phenols, and thiophenols it has been found that N—H, O—H and S—H bond dissociation enthalpies (BDE) depend on Hammett constants approximately linearly. For substituents placed in <italic>meta</italic> position, linearity of found dependences is usually considerably worse in comparison to <italic>para</italic>-substituted molecules. Therefore, their applicability for prediction of changes in BDE using substituent Hammett constant may be limited. In this work, we have found that the length of thiophenolic C—S bond, <italic>R</italic>(C—S), or its shortening after hydrogen atom abstraction, Δ<italic>R</italic>(C—S), represent suitable descriptors of substituent induced changes in S—H BDE. For fifteen studied <italic>meta</italic>-substituted thiophenols, these geometry descriptors correlate with S—H BDEs considerably better than Hammett constants.</p></abstract>

For mono-substituted anilines, phenols, and thiophenols it has been found that N—H, O—H and S—H bond dissociation enthalpies (BDE) depend on Hammett constants approximately linearly. For substituents placed in meta position, linearity of found dependences is usually considerably worse in comparison to para-substituted molecules. Therefore, their applicability for prediction of changes in BDE using substituent Hammett constant may be limited. In this work, we have found that the length of thiophenolic C—S bond, R(C—S), or its shortening after hydrogen atom abstraction, ΔR(C—S), represent suitable descriptors of substituent induced changes in S—H BDE. For fifteen studied meta-substituted thiophenols, these geometry descriptors correlate with S—H BDEs considerably better than Hammett constants.

S—H Bond Dissociation Enthalpies in <italic>para</italic>- and <italic>meta</italic>-Substituted Thiophenols: Correlation with Thiophenolic C—S Bond Length

Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology, Radlinského 9, SK-812 37 Bratislava, Slovakia

Acta Chimica Slovaca

S—H Bond Dissociation Enthalpies in - and -Substituted Thiophenols: Correlation with Thiophenolic C—S Bond Length

For mono-substituted anilines, phenols, and thiophenols it has been found that N—H, O—H and S—H bond dissociation enthalpies (BDE) depend on Hammett constants...

S—H Bond Dissociation Enthalpies in para- and meta-Substituted Thiophenols: Correlation with Thiophenolic C—S Bond Length

Publié en ligne: 14 mai 2012

Pages: 37 - 41

DOI: https://doi.org/10.2478/v10188-012-0006-2

Mots clés
DFT/B3LYP, Bond dissociation enthalpy, Thiophenol, Substituent effect, C—S bond length

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