Thermochemical study of two N-benzoyl-N′,N′-dialkylureas

The standard (p(o) = 0.1 MPa) molar enthalpies of combustion in oxygen of crystalline N-benzoyl-N',N'-diethylurea, PhCONHCON(Et)(2) (HBETU) and N-benzoyl-N',N'- diisobutylurea, PhCONHCON(iBu)(2) (HBIBU), were measured at T = 298.15 K by static bomb combustion calorimetry. The standard molar enthalpies of sublimation of both compounds were measured using microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively. -Delta (c)u(o)(cr)/(J . g(-1)) Delta H-g(cr)m(o)(kJ . mol(-1)) N-benzoyl-N',N'-diethylurea 29756.9 +/- 9.6 132.2 +/- 1.4 N-benzoyl-N',N'-diisobutylurea 33047.0 +/- 9.3 137.5 +/- 2.9 (C) 2000 Academic Press.