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

The standard (p(o) = 0.1 MPa) molar enthalpies of combustion in oxygen of c rystalline N-benzoyl-N',N'-diethylurea, PhCONHCON(Et)(2) (HBETU) and N-benz oyl-N',N'- diisobutylurea, PhCONHCON(iBu)(2) (HBIBU), were measured at T = 298.15 K by static bomb combustion calorimetry. The standard molar enthalpi es of sublimation of both compounds were measured using microcalorimetry. T hese 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 Acade mic Press.