Determination of the substituent constant σp- for the thioamide group -CSNH2 from the ionization of anilines and phenols
- 1 January 1991
- journal article
- Published by Institute of Organic Chemistry & Biochemistry in Collection of Czechoslovak Chemical Communications
- Vol. 56 (12) , 2964-2968
- https://doi.org/10.1135/cccc19912964
Abstract
Thermodynamic ionization constants pKa 2.62 ± 0.01 for the primary aromatic amino group of 4-aminothiobenzamide and pKa 8.28 ± 0.01 for the phenolic hydroxy group of 4-hydroxythiobenzamide have been determined by ultra-violet spectrophotometry at 25°C. By using these pKa values and the Hammett equations (log Ka vs σ) for the ionization of fourteen 3- or 4-substituted phenols and thirteen 3- or 4-substituted anilines the substituent constant σp- = 0.68 (from the ionization of anilines) or σp- = 0.73 (from the ionization of phenols) of the thioamide group -CSNH2 was calculated.Keywords
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