Current Organic Chemistry - Volume 15, Issue 20, 2011

The wave picture of the electron implies an always present electron delocalization. This electronic delocalization is not an observable, and therefore there is not an experimental property that allows measuring it directly. However, electronic delocalization reveals itself in several chemical phenomena that can be experimentally interrogated to have a measure of the degree of electron delocalization in our system. From a t Read More

The utility of the localization and localizability concepts for describing chemical situation is discussed. Two routes can be followed to get such a picture from wave functions which are in principle delocalized in nature. On the one hand are orbital localization techniques which are described in the context of their applicability to organic chemistry problems. On the other hand are methods relying on local functions which perform Read More

Here, we provide an essay on the analysis of the reaction mechanism at the molecular level; in particular, the evolution of the electron pair, as it is provided by the ELF, is used to decribe the reaction pathway. Then, the reaction mechanism is determined by the topological changes of the ELF gradient field along a series of structural stability domains. From this analysis, concepts such as bond breaking/forming processes, form Read More

The ellipticity of the electron density at the bond critical points is a parameter computed in the framework of the Atoms in Molecules (AIM) analysis. This parameter provides a quantitative measurement of the anisotropy of the electron density at the BCP. The ellipticity has been originally associated to the π character of bonds, and therefore, it has been also employed as a measurement of delocalization and, ultimately, ar Read More

Since in 1938 Evans and Warhurst established the analogy between electron delocalization in the transition structure of the Diels- Alder reaction and in benzene, many studies have been carried out to combine the concept of aromaticity with the Woodward- Hoffmann rules for thermally allowed pericyclic reactions. This review includes first a brief survey of the main aromaticity descriptors that have been applied successf Read More

The concept of localization and delocalization in molecules is discussed in terms of the response of the electronic system to an external perturbation. It is argued that both the spatial organization of electrons in pairs and the spatial distribution of the response intensity, reflect main features of the correlated motion of electrons, ultimately described by the pair distribution function of electrons. Various measures, deri Read More

The Electron Localization Function (ELF) has played in the last time an important role in understanding the special characteristics of the chemical bond. The chemical interpretation of the ELF as an indicator of the regions of the space where it is most probable to find a localized electron pair has been of great value in order to understand some complex chemical bonds. In this work, the ELF has been used to study the delocaliz Read More

Electron delocalization is a fundamental concept in chemistry. It is deeply rooted in many important chemical phenomena e.g. aromaticity, conjugation and the reactivity of a vast number of inorganic, organometallic and organic compounds. This review focuses on those theoretical studies in which electron delocalization indicators provide valuable insigths in the understanding of electrophilic aromatic substitutions. T Read More