Solvation behaviour and micro-phase structure of formaldehyde-methanol-water mixtures

Solvation of formaldehyde as methanediol and/or methoxymethanol in methanol-water mixtures of varying concentration was studied using classical molecular dynamics simulations. Varying strength of hydrophobic and hydrophilic interactions affect the arrangement of solvent within the solvation shell. Ether oxygen of methoxymethanol was observed to be hydrophobic in nature with hydrophilic interactions weaker than bulk due to the steric hindrance by the methyl group. At equimolar methanol-water compositions, water is more likely to occupy the hydrophilic sites. The total number of hydrogen bonds formed between solute and solvent decreased non-linearly, which was attributed to formaldehyde forming a distribution of different metastable complexes and micro-phase ordering. This non-linearity may influence the energetics of these solutions. The lifetime of hydrogen bonding was studied to build an understanding of the strength of hydrophilic interactions. The arrangement of methanol and water around solvated formaldehyde was visualised using spatial distribution function.