Enthalpies and entropies of melting from differential scanning calorimetry and freezing point depressions: urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, tetramethylurea, and thiourea

• Published in: Thermochimica acta 1972, Vol.5 (1), p.21-24
• Main Authors: Zordan, T.A., Hurkot, D.G., Peterson, M., Hepler, L.G.
• Format: Article
• Language: English
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/0040-6031(72)80014-5

The following enthalpies of melting have been determined with a differential scanning calorimeter: urea, 3.22 kcal mole −1; 1,3-dimethylurea, 2.97 kcal mole −1; methylurea, 3.34 kcal mole −1: 1,1-dimethylurea, 5.49 kcal mole −1; thiourea, 3.30 kcal mole −1. Freezing point depression measurements have led to the following enthalpies of melting: benzoic acid, 4.29 kcal mole −1: urea, 3.30 kcal mole −1; 1,3-dimethylurea, 3.11 kcal mole −1; tetramethylurea, 3.37 kcal mole −1. The results above lead to the following entropies of melting: urea, 8.00 cal deg −1 mole −1; methylurea, 8.90 cal deg −1 mole −1; 1,1-dimethylurea, 12.06 cal deg −1 mole −1; 1,3-dimethylurea, 7.95 cal deg −1 mole −1; tetramethylurea, 12.39 cal deg −1 mole −1; thiourea, 7.28 cal deg −1 mole −1.