Journal of Chemical Thermodynamics, Vol.40, No.9, 1342-1345, 2008
Enthalpies of solution of N,N,N',N'-tetramethylurea in amides, dimethylsulphoxide, and acetone at 298.15 K
The enthalpies of solution Delta H-sol(m)m were determined for N,N,N',N'-tetramethylurea in formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, and acetone. Measurements were made at 298.15 K and molalities m = (0.004 to 0.031) mol . kg(-1) with a precise isoperibol ampoule-type calorimeter. Standard enthalpies of solution Delta H-sol(m)degrees and transfer Delta H-tr(m)degrees from one solvent to another were computed. The enthalpies of solution of the solute in the hydrogen-non-bonding media were found to be endothermic and weak depending on the nature of methylation in a solvent molecule. It was concluded that the solvent proton-donor ability and existing steric hindrances for hydrogen bonding and other intermolecular interactions play the key role in solvation of tetramethylurea. (C) 2008 Elsevier Ltd. All rights reserved.
Keywords:Enthalpies of solution and transfer;Tetramethylurea;Formamide and its methyl-substituted analogues;Dimethylsulphoxide and acetone