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KMID : 1059519840280040210
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Journal of the Korean Chemical Society
1984 Volume.28 No. 4 p.210 ~ p.216
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Solvation in Mixed Solvent (III). Solvatochromic Analysis for the Solvent Effect of Binary Mixed Solvent
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Lee Ik-Choon
Lah Sang-Moo
Lee Bon-Su
Sohn Se-Chul
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Abstract
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Solvatochromic comparison methods were applied to determine Taft's solvent parameters, π*(solvent polarity-polarizability), α(solvent hydrogen bond donor acidity) and β (solvent hydrogen bond acceptor basicity) for MeOH-MeCN solvent mixtures. Swain's solvent parameters A(anion solvation scale) and B(cation solvation scale) were also determined by least square fitting of kinetic data in the same binary solvent mixtures. It was found that: (ⅰ) β depends on the basicity of the solvent and inceases with the MeOH content owing to the increase in polymeric structure of methanol; (ⅱ)π*depends on the dipole moment of the solvent and increases with the MeCN content of the solvent; (ⅲ) α increases rapidly with the MeOH content as the hydrogen bond donor acidity of the solvent mixtures increases. Taft's reaction constants a and s and Swain's reaction constants a and b were determined for the reactions reported from our laboratory previously using solvent parameters determined in this work. No meaningful inter-relationship was found between the two set of reaction parameters, but a good linear correlation was found between the ratios a/s and a/b. Solvent effect on the reaction mechanism, substituent effect and leaving group ability were examined in the light of these reaction constants ratios.
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