2012 |
Cedillo, A; Contreras, R A Local Extension of the Electrophilicity Index Concept Artículo de revista Journal of the Mexican Chemical Society, 56 (3), pp. 257-260, 2012, ISSN: 1870-249x. Resumen | Enlaces | BibTeX | Etiquetas: chemical chemical-reactivity, concept, density density-functional descriptors, electrophilicity, fukui function, functional hardness, intermolecular local parameter philicity reactivity, selectivity, softness, theory @article{RN107, title = {A Local Extension of the Electrophilicity Index Concept}, author = { A. Cedillo and R. Contreras}, url = {/brokenurl#<Go to ISI>://WOS:000311506100005}, issn = {1870-249x}, year = {2012}, date = {2012-01-01}, journal = {Journal of the Mexican Chemical Society}, volume = {56}, number = {3}, pages = {257-260}, abstract = {A local measure of the electrophilicity has been recently proposed to analyze the chemical reactivity of several kinds of molecules. In this work a theoretical rationalization of the local extension is proposed following the quantitative definition of the molecular electrophilic power and a variational method for the distribution of the transferred charge. A condensation scheme to atoms or fragments follows from its relation to the Fukui function and the local softness. Differences between these quantities are discussed and they are tested in a model system. The analysis shows that the local electrophilicity is more appropriate to describe differences among a set of substituted molecules.}, keywords = {chemical chemical-reactivity, concept, density density-functional descriptors, electrophilicity, fukui function, functional hardness, intermolecular local parameter philicity reactivity, selectivity, softness, theory}, pubstate = {published}, tppubtype = {article} } A local measure of the electrophilicity has been recently proposed to analyze the chemical reactivity of several kinds of molecules. In this work a theoretical rationalization of the local extension is proposed following the quantitative definition of the molecular electrophilic power and a variational method for the distribution of the transferred charge. A condensation scheme to atoms or fragments follows from its relation to the Fukui function and the local softness. Differences between these quantities are discussed and they are tested in a model system. The analysis shows that the local electrophilicity is more appropriate to describe differences among a set of substituted molecules. |
Ormazabal-Toledo, R; Castro, E A; Santos, J G; Millan, D; Canete, A; Contreras, R; Campodonico, P R Predicting the Reaction Mechanism of Nucleophilic Substitutions at Carbonyl and Thiocarbonyl Centres of Esters and Thioesters Artículo de revista Journal of Physical Organic Chemistry, 25 (12), pp. 1359-1364, 2012, ISSN: 0894-3230. Resumen | Enlaces | BibTeX | Etiquetas: aminolysis, carbonyl carboxylic center, contrasting density derivatives, dithiocarbonates, electron electrophilic esters, fukui function, group group, kinetic kinetics, leaving measurements, mechanisms, o-ethyl phenyl, reaction reactivity, reorganization, secondary @article{RN103, title = {Predicting the Reaction Mechanism of Nucleophilic Substitutions at Carbonyl and Thiocarbonyl Centres of Esters and Thioesters}, author = { R. Ormazabal-Toledo and E.A. Castro and J.G. Santos and D. Millan and A. Canete and R. Contreras and P.R. Campodonico}, url = {/brokenurl#<Go to ISI>://WOS:000313125800038}, doi = {10.1002/poc.3048}, issn = {0894-3230}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Organic Chemistry}, volume = {25}, number = {12}, pages = {1359-1364}, publisher = {2012 John Wiley & Sons, Ltd.}, abstract = {In nucleophilic substitution reactions at carbonyl centres, there are two possible channels. The first one occurs when the attack of nucleophilic agents takes place simultaneously with the departure of the nucleofuge. This process is named as concerted. The second possibility is the formation of a reaction intermediate, typically a tetrahedral intermediate from which the nucleofuge departs after passing through a second transition state. This second mechanism is defined as stepwise. Whether a concerted or stepwise mechanism is to be expected for a given reaction depends on several factors. Among these determinants are the nucleophilicity of the attacking group, the leaving group ability of the nucleofuge, and the solvent, which affects both the stability of the intermediate or the transition states involved. The role of the electrophilic centre can however become an important factor that can determine the reaction mechanism. In this work we show that the group nucleophilic Fukui function model may be used to rationalize and to predict the reaction mechanism of the title compounds towards alicyclic amines. In general, when the electrophilic carbon centre is attached to the soft sulfur atom, the reaction mechanism is predicted to follow a stepwise route. When the electrophilic carbon atom is attached to a harder oxygen centre, the reaction mechanism is determined by chemical substitution at the nucleofuge moiety. Experimental verification for a set of four substrates is presented.}, keywords = {aminolysis, carbonyl carboxylic center, contrasting density derivatives, dithiocarbonates, electron electrophilic esters, fukui function, group group, kinetic kinetics, leaving measurements, mechanisms, o-ethyl phenyl, reaction reactivity, reorganization, secondary}, pubstate = {published}, tppubtype = {article} } In nucleophilic substitution reactions at carbonyl centres, there are two possible channels. The first one occurs when the attack of nucleophilic agents takes place simultaneously with the departure of the nucleofuge. This process is named as concerted. The second possibility is the formation of a reaction intermediate, typically a tetrahedral intermediate from which the nucleofuge departs after passing through a second transition state. This second mechanism is defined as stepwise. Whether a concerted or stepwise mechanism is to be expected for a given reaction depends on several factors. Among these determinants are the nucleophilicity of the attacking group, the leaving group ability of the nucleofuge, and the solvent, which affects both the stability of the intermediate or the transition states involved. The role of the electrophilic centre can however become an important factor that can determine the reaction mechanism. In this work we show that the group nucleophilic Fukui function model may be used to rationalize and to predict the reaction mechanism of the title compounds towards alicyclic amines. In general, when the electrophilic carbon centre is attached to the soft sulfur atom, the reaction mechanism is predicted to follow a stepwise route. When the electrophilic carbon atom is attached to a harder oxygen centre, the reaction mechanism is determined by chemical substitution at the nucleofuge moiety. Experimental verification for a set of four substrates is presented. |
2012 |
A Local Extension of the Electrophilicity Index Concept Artículo de revista Journal of the Mexican Chemical Society, 56 (3), pp. 257-260, 2012, ISSN: 1870-249x. |
Predicting the Reaction Mechanism of Nucleophilic Substitutions at Carbonyl and Thiocarbonyl Centres of Esters and Thioesters Artículo de revista Journal of Physical Organic Chemistry, 25 (12), pp. 1359-1364, 2012, ISSN: 0894-3230. |