Local Softness and Hardness Based Reactivity Descriptors for Predicting Intra- and Intermolecular Reactivity Sequences: Carbonyl Compounds

Abstract

The DFT-based reactivity descriptors “local softness” and “local hardness” are used as reactivity indices to predict the reactivity sequences (both intramolecular and intermolecular) of carbonyl compounds toward nucleophilic attack on them. The finite difference approximation is used to calculate local softness, whereas local hardness is approximated by −V el/2N, where V el is the electronic part of the molecular electrostatic potential. Both aldehydes and ketones, aliphatic and aromatic, have been selected as systems. Critical cases, e.g., C6H5CHCHCHO, CH3CHCHCHO, and CH2CHCHO, where a CC double bond is in conjugation with the CO group, are also considered. Two new reactivity descriptors are proposed, “relative electrophilicity” (s k +/s k -) and “relative nucleophilicity” (s k -/s k +), which will help to locate the preferable reactive sites. Our results show that local hardness can be used as a guiding parameter when constructing intermolecular reactivity sequences.

Application of the Reactivity Index to Propose Intra and Intermolecular Reactivity in Metal Cluster Interaction over Oxide Surface

“…A gradient corrected functional BLYP 44,45) and DNP basis set 46) was used through out the calculation. Basis set superposition error (BSSE) was also calculated for the current basis set in nonlocal density approximation (NLDA).…”

“…The Fukui function and local softness for the hydroxyl proton is presented both in terms of nucleophilic and electrophilic activity. Roy et al 46) have introduced relative electrophilicity (s x þ /s x À ) and relative nucleophilicity (s x À /s x þ ). These can be defined as the electrophilicity of any site as compared to its own nucleophilicity for the first term and vice versa.…”

Global and Local Reactivity Descriptors Based on Quadratic and Linear Energy Models for α,β-Unsaturated Organic Compounds

“…Finally, for each of the atomic condensed values of the Fukui function (FMR and RMF) we alternatively also calculated the condensed, linear, local softness defined as [46,47,48] …”

“…Accounting for the difference in the global softness between molecules, the local softness was proposed to be more suitable for the comparison of local reactivities between molecules with differ considerably in size [46,47,48].…”

Synthesis, Crystallographic Characterization and Density Functional Study of Novel Spoke-Molecular Tetravent ethyltriphenylphosphorous Dibromide

“…The hardness of the spoke form is relatively larger than that of the ionic form while the ionic form is softer than the molecular form. Since softness and hardness can be employed to examine relative reactivity of substances 53 , one would assume that the ionic form is more likely reactive than the spoke one. That's might shed the light on the fact that the di-ionic form has been prepared long time before the spoke one and amazingly employed as it is aforementioned.…”