A new approach to local hardness

The applicability of the local hardness as defined by the derivative of the chemical potential with respect to the electron density is undermined by an essential ambiguity arising from this definition. Further, the local quantity defined in this way does not integrate to the (global) hardness - in contrast with the local softness, which integrates to the softness. It has also been shown recently that with the conventional formulae, the largest values of local hardness do not necessarily correspond to the hardest regions of a molecule. Here, in an attempt to fix these drawbacks, we propose a new approach to define and evaluate the local hardness. We define a local chemical potential, utilizing the fact that the chemical potential emerges as the additive constant term in the number-conserving functional derivative of the energy density functional. Then, differentiation of this local chemical potential with respect to the number of electrons leads to a local hardness that integrates to the hardness, and possesses a favourable property; namely, within any given electron system, it is in a local inverse relation with the Fukui function, which is known to be a proper indicator of local softness in the case of soft systems. Numerical tests for a few selected molecules and a detailed analysis, comparing the new definition of local hardness with the previous ones, show promising results.Comment: 30 pages (including 6 figures, 1 table

Applications of the Conceptual Density Functional Theory Indices to Organic Chemistry Reactivity

Indexación: Web of ScienceTheoretical reactivity indices based on the conceptual Density Functional Theory (DFT) have become a powerful tool for the semiquantitative study of organic reactivity. A large number of reactivity indices have been proposed in the literature. Herein, global quantities like the electronic chemical potential μ, the electrophilicity ω and the nucleophilicity N indices, and local condensed indices like the electrophilic and nucleophilic Parr functions, as the most relevant indices for the study of organic reactivity, are discussed.http://www.mdpi.com/1420-3049/21/6/74

On the Predictive Power of Chemical Concepts

Many chemical concepts can be well defined in the context of quantum chemical theories. Examples are the electronegativity scale of Mulliken and Jaffe and the hard and soft acids and bases concept of Pearson. The sound theoretical basis allows for a systematic definition of such concepts. However, while they are often used to describe and compare chemical processes in terms of reactivity, their predictive power remains unclear. In this work, we elaborate on the predictive potential of chemical reactivity concepts, which can be crucial for autonomous reaction exploration protocols to guide them by first-principles heuristics that expoit these concepts.Comment: 23 pages, 1 figure, 1 tabl

Theoretical Studies of the Chemical Reactivity of a Series of Coumarin Derivatives by the Density Functional Theory

The global descriptors of reactivity such as HOMO and LUMO energies, chemical hardness, electrophilicity, softness and dipole moment are theoretically determined for five coumarin derivatives in this paper. The analysis of the determined descriptors allows us to classify the studied molecules according to their reactivities. Thus, compound M3 is qualified to be the most reactive and the least stable with 3.933 eV as its gap energy ΔEgap. It is at the same time the softest, the best electron donor, the most electrophilic and the most polar molecule. The study of thermodynamic parameters shows that all the reactions of formation of studied coumarin derivatives are exothermic and spontaneous with less disorder. Furthermore, Hirschfield population analysis was carried out in order to locate the reactive sites, that are assumed to be the electrophilic and nucleophilic sites of the molecules. It appears that all the reactive sites are located on carbon atoms except those of molecule M3 which are located on oxygen atoms. Compounds M1 and M2 have the same electrophilic site (C15) and the same nucleophilic site (C13) thereby showing that the methyl group does not have any influence on the reactive site. The electrophilic site of the molecule M3 is located on both the identical oxygen atoms O33 and O34 while its nucleophilic site is located on the oxygen atoms O12. The electrophilic sites of compound M4 and M5 are the same and it is located on carbon atom(C11) while the nucleophilic site is located on carbon atom C23 for molecule M4. Concerning the nucleophilic sites of molecule M5 it is located on carbon atom C20. The difference nucleophilic reactive site may be due to the conjugation of activity of both fluorine atom and methyl group on the M5

Theoretical prediction of solubility, reactivity and degradation pathways of selected azo disperse dyes

Abstract :Ph.D. (Chemistry