DFT Studies Using B3LYP/6-31 G* Level of theory for the Evaluation of Global and Local Electrophilicity Descriptors for the Prediction of Reaction Mechanism of Diels-Alder Reaction

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Abstract:

Computational chemistry is a very significant tool for the prediction and undersatnding of reaction mechanisms and behavior of reagents. Global and local reactivity descriptors proposed by Parr et al. have been proved to be are very important and reliable tool for the prediction of mechanism and reactivity of Diels-Alder reactions. In this regards, we have deteremined a number of global and local reactivity descriptors viz., electrophilicity index ω, chemical potential μ, chemical softness S, chemical hardness η etc. for various dienes and dienophiles to understand their participation in Diels-Alder reaction. These studies were performed at  DFT B3LYP/6-31G* level of theory. Moreover electrophilic (fk+) & nucleophilic fukui (fk-) functions along with Parr functions have also been evaluated to predict the regioselectivity of cycloaddition processes. Further, the transition states were determined for different cycloadducts using QST2 approach and confirmed by IRC analysis and negative imaginary frequency. The activation energy barriers, thermodynamic parameters viz., ∆G, ∆S and ∆H were also calculated to explain the mechanistic aspects of cycloaddition reaction. The results were found to be quite useful for the prediction of Diels-Alder cycloaddition reactions.

Keywords:

DFT, Global and local electrophilicity descriptors, Diels-alder reaction.