Studies of intermolecular force coefficient (σimf) for methyl derivatives of urea in aqueous solutions with Friccohesity, a new physicochemical function, from 293.15 to 303.15 K

Chemistry Research Lab, Deshbandhu College, University of Delhi, New Delhi-110 019, India
E-mail : mansingh50@hotmail.com
Manuscript received 6 June 2005

Both surface tension (ϒ) and viscosity (ɳ) for 0.0050 to 0.2560 kg mol^-1 urea, methylurea and dimethylurea solutions
have been measured with Survismeter for Friccohesity (σ/Sm^-1), derived from frictional and cohesive forces. The limiting
(σ⁰) and slope values S_σ of σ at infinite dilution, m = 0, are determined from σ vs m mol kg^-1 fit for intermolecular
forces coefficient (σ⁰imf) and influence of temperature, K. The S_σ values project an effect of concentrations on pairwise
interactions of ureas. And decrease in σ⁰_imf and S_σ values from urea to dimethylurrea focus contribution of -CH₃ group
to hydrophobic interactions over the hydrophilic, due to -NH₂ and >CO- groups of urea. Substitution of H by -CH₃ is
noted to weaken hydrogen bonding strength of >CO-.