Effect of Polarity on the Interaction Energies of some Organic Solvent (OS)-Water System and Formation of Donor-acceptor Complex: Quantum Mechanical MP4 Study

Long-range or short-range van der Waals interaction in organic solvents (OS) is quite common; but, when an organic solvent or molecule directly interacts with a water molecule then it shows a significant change in the stability of such solvent-water system. Polar organic solvent/molecule shows strong hydrogen bonding interaction in aqueous phase whereas nonpolar solvent shows very weak interaction. In organic solvent-water complexes, solvent plays a very important role in the stability of such system, sometimes the solvent will interact with water molecule as proton donor or sometimes it will interact as proton acceptor mode. In gas phase, some common organic solvents such as aldehyde, ketone, carboxylic acid, cyclohexanol, amine, aniline, amide, etc. may interact with water molecules through different ways and we try to investigate the relative stability and actual mode of interaction of such organic solvent(OS)-water complexes by using computational method. Solvent polarity also plays an important role in such organic solvent (OS)-water complexes; therefore, the effect of polarity on the interacting counterpart need to study by changing the dielectric constant of the solvent system and thus it is necessary to analyze the effect of solvent on such OS-water systems. Quantum mechanical method, Møller-Plesset (MP) perturbation theory is an important and accurate tool for computing the interaction energy between the organic solvent-water complexes. The minute details of electron transfer pathway and donor-acceptor mechanism of such OS-water complexes have been studied by calculating single point energy and Natural Bond Orbital (NBO) analysis using MP4 methods.