Equilibrium constants and protonation site for N-methylbenzenesulfonamides
Please use this identifier to cite or link to this item:
http://hdl.handle.net/10347/22450
Files in this item
Metadata
Title: | Equilibrium constants and protonation site for N-methylbenzenesulfonamides |
Author: | Moreira, José A. Costa, Ana M. Rosa da García Río, Luis Pessêgo, Márcia Isabel Duarte |
Affiliation: | Universidade de Santiago de Compostela. Centro de Investigación en Química Biolóxica e Materiais Moleculares Universidade de Santiago de Compostela. Departamento de Química Física |
Subject: | Linear free-energy relationships | N-methylbenzenesulfonamides | Protonation equilibrium | |
Date of Issue: | 2011 |
Publisher: | Beilstein Institute |
Citation: | Moreira, J. A.; Rosa da Costa, A. M.; García-Río, L.; Pessêgo, M. Beilstein J. Org. Chem. 2011, 7, 1732–1738. doi:10.3762/bjoc.7.203 |
Abstract: | The protonation equilibria of four substituted N-methylbenzenesulfonamides, X-MBS: X = 4-MeO (3a), 4-Me (3b), 4-Cl (3c) and 4-NO2 (3d), in aqueous sulfuric acid were studied at 25 °C by UV–vis spectroscopy. As expected, the values for the acidity constants are highly dependent on the electron-donor character of the substituent (the pKBH+ values are −3.5 ± 0.2, −4.2 ± 0.2, −5.2 ± 0.3 and −6.0 ± 0.3 for 3a, 3b, 3c and 3d, respectively). The solvation parameter m* is always higher than 0.5 and points to a decrease in the importance of solvation on the cation stabilization as the electron-donor character of the substituent increases. Hammett plots of the equilibrium constants showed a better correlation with the σ+ substituent parameter than with σ, which indicates that the initial protonation site is the oxygen atom of the sulfonyl group |
Publisher version: | https://doi.org/10.3762/bjoc.7.203 |
URI: | http://hdl.handle.net/10347/22450 |
DOI: | 10.3762/bjoc.7.203 |
ISSN: | 1860-5397 |
Rights: | © 2011 Moreira et al; licensee Beilstein-Institut. This is an Open Access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited |
Collections
-
- CIQUS-Artigos [404]
- QF-Artigos [111]
Except where otherwise noted, this item's license is described as © 2011 Moreira et al; licensee Beilstein-Institut. This is an Open Access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited