Studies of the Chemical Reactivity of a Series of Benzimidazolyl-Chalcone by Quantum Chemical Approaches

Abstract

This theoretical chemical reactivity study was conducted using the Density Functional Theory (DFT) method at the B3LYP/6-311G(d,p) level of calculation. It involved a series of five (05) Benzimidazolyl-Chalcone (BZC) and allowed the prediction of the chemical reactivity of these compounds. The DFT global chemical reactivity descriptors (HOMO and LUMO energies, chemical hardness, energy, electronic chemical potential and electrophilicity) were examined to predict the relative stability and reactivity of BZCs. Thus BZC-4 which has a boundary orbital energy gap of ΔEgap = 3.650 eV is the most polarisable, most reactive, good nucleophile.and it is a soft molecule. The values of the global reactivity descriptors confirmed the high chemical reactivity of BZC-4. Local reactivity indices as well as dual descriptors were calculated to indicate the likely sites of electrophilic and nucleophilic attack of the different compounds studied. The analysis of the local indices and the dual descriptors revealed that the nitrogen heteroatom N13 is the preferential site of electrophilic attack and the carbon atom C1 should be the most reactive site with respect to a nucleophilic attack. the Hierarchical Ascending Classification analysis allowed us to group all five (5) compounds studied into three categories. The most active which are BZC-1 and BZC-5, the moderately active BZC-2, and the compounds BZC-3 and BZC-4, the least active. Moreover, this classification is consistent with the value of the Larvicide concentrations (LC100 (μg/mL)).
 Keywords : Benzimidazolyl-Chalcone (BZC), Global descriptors, Local descriptors, Dual descriptors