NCI concept as a powerful tool to investigate the origin of Diels-Alder reaction accelerating inside the self-assembled softball nanoreactor

Thermodynamic and kinetic aspects of the Diels-Alder reaction between p-benzoquinone (1) and cyclohexadiene (2) have been investigated inside the softball nanoreactor, theoretically. The softball nanoreactor has remarkable effects on the possibility and facility of the inside reaction. Wall atoms effects of the nanoreactor on the reaction have been investigated by the evaluation of the non-covalent interactions (NCI) analysis. In addition, the hydrogen bond character of the bonds between the monomers of the nanoreactor, as a driving force for the nanoreactor construction, has been studied by topological analysis of the nanoreactor, electron localization function and localized orbital locator criteria. Two kinds of the hydrogen bond have been confirmed between the monomers of the nanoreactor by using the 2D and 3D NCI plots. NBO analysis has been applied for justification of these hydrogen bond formation. Finally, it has been concluded that the molecular nanoreactor accelerates Diels-Alder reaction through the van der Waals interactions with the reactants and transition states.