Computational Nanochemistry Report on the Oxicams—Conceptual DFT Indices and Chemical Reactivity

Abstract

A density functional theory study of eight oxicams was carried out in order to determine their global and local reactivities. These types of reactivities were measured by means of global and local reactivity descriptors coming from the conceptual density functional theory. Net electrophilicity as a global reactivity descriptor and local hypersoftness as a local reactivity descriptor were the used tools to distinguish reactivity and selectivity among these oxicams. Globally, isoxicam presents the highest electron donating capacity; meanwhile, the highest electron accepting capacity is exhibited by droxicam. Locally, two oxicams present neither nucleophilic nor electrophilic relevant reactivity in their peripheral pyridine ring, droxicam and tenoxicam, so that their more reactive zones are found on the respective fused rings. Oxicams have been divided into two subgroups in order to facilitate the local analysis of reactivity. One group is characterized because their most important condensed values for local hypersoftnes are well-separated: 4-meloxicam, lornoxicam, meloxicam, and normeloxicam. Meanwhile, the opposite situation is found in droxicam, isoxicam, piroxicam, and tenoxicam. As a whole, the nucleophilic characteristic noticeably predominates in these eight oxicams instead of an electrophilic behavior, thus meaning a greater tendency to donate electrons rather than withdrawing them; a consequence of this behavior implies a favorable interaction with a hypothetical receptor bearing one or more electron acceptor functional groups rather than electron donor functional groups; this would imply a maximization of this interaction from the covalent point of view.

Molecular Modeling of the Structures, Properties and Glycating Power of Some Reducing Disaccharides

“…Following the lines of our previous work and it has been described in detail before, [8][9][10][11][12][13][14] all computational studies were performed with the Gaussian 09 [24] series of programs with density functional methods as implemented in the computational package. The equilibrium geometries of the molecules were determined by means of the gradient technique.…”

“…As this work is part of an ongoing project, the theoretical background is similar to that presented in previous research and has been described in detail before [8][9][10][11][12][13][14][15][16], the chemical potential μ is defined as:…”

“…The condensed dual descriptor has been defined as [18,19]: ( 9 ) From the interpretation given to the Fukui function, one can note that the sign of the dual descriptor is very important to characterize the reactivity of a site within a molecule toward a nucleophilic or an electrophilic attack. That is, if (10) Then the site is favored for a nucleophilic attack, whereas if (11) Then the site may be favored for an electrophilic attack [18][19][20].…”

“…That is, if (10) Then the site is favored for a nucleophilic attack, whereas if (11) Then the site may be favored for an electrophilic attack [18][19][20].…”

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“…As this work is part of an ongoing project, the theoretical background will be analog to that presented in previous research [12][13][14][15][16][17][18] and will be shown here for the sake of completeness. Within the conceptual framework of DFT [19,20], the chemical potential  is defined as:…”