An estimation of hydrophilic and hydrophobic interaction of aqueous urea, methylurea, dimethylurea and tetramethylurea from density and apparent molal volume at 30.0°C

Abstract

Density (ρ) for 0.20–1.0 mol kg−1 of urea, 1-methylurea, 1,3-dimethylurea and 1,1,3,3-tetramethylurea solutions have been measured at an interval of 0.2 mol kg−1. Apparent molal volume (V φ, cm3 mol−1) is calculated from ρ values. Primary data were regressed and extrapolated to zero concentration for the limiting density (ρ0) and limiting apparent molal volume values for solute–solvent interactions.–CH3 (methyl) groups of N-methylureas weaken hydrophilic interaction and enhance hydrophobic interaction. The value of ρ0 and reflect the intermolecular forces due to electrostatic charge. The decreasing value of ρ0 and increasing value of with increasing number of–CH3 groups suggest some weak hydrophilic and strong hydrophobic interactions, so that the structure-breaking effect decreases. It was also found that with increasing concentration, the hydrophilic or hydrophobic interactions become stronger.