Microsolvation of methyl hydrogen peroxide: Ab initio quantum chemical approach

Methyl hydrogen peroxide (MHP), one of the simplest organic hydroperoxides, is a strong oxidant, with enhanced activity in aqueous ambience. The present study investigates, at the molecular level, the role of hydrogen bonding that is conducive to cluster formation of MHP with water molecules from its peroxide end, with the methyl group remaining hydrophobic for up to five water molecules. Ab initio quantum chemical computations on $MHP⋯(H2O)n$⁠, $[n=1–5]$ are performed at second order Møller–Plesset (MP2) perturbation theory employing the basis sets 6-31G(d,p) and $6-311++G(2d,2p)$ to study the cluster formation of MHP with water molecules from its peroxide end and hydrophobic hydration due to the methyl group. Successive addition of water molecules alters the hydrogen bonding pattern, which leads to changes in overall cluster geometry and in turn to IR vibrational frequency shifts. Molecular co-operativity in these clusters is gauged directly through a detailed many-body interaction energy analysis. Molecular electrostatic potential maps are shown to have a bearing on predicting further growth of these clusters, which is duly corroborated through sample calculations for $MHP⋯(H2O)8$⁠. Further, a continuum solvation model calculation for energetically stable clusters suggests that this study should serve as a precursor for pathways to aqueous solvation of MHP.