ABSTRACT

Thermophysical and thermochemical studies have been carried out for crystalline parabanic acid. The thermophysical study was made by differential scanning calorimetry, DSC, over the temperature interval between T = (263 and 473) K. Two phase transitions were found: at T = (392.3 +- 1.6) K with the enthalpy of transition of (2.1 +- 0.4) kJ mol 1 and at T = (509.8 +- 1.5) K, when the compound was scanned to its fusion temperature. The standard (p = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, for crystalline parabanic acid was determined using static-bomb combustion calorimetry as (590.2 +- 1.0) kJ mol 1. The standard molar enthalpy of sublimation, at T = 298.15 K, was derived from the variation of their vapour pressures, measured by the Knudsen-effusion method, with the temperature. These two thermochemical parameters yielded the standard molar enthalpy of formation in the gaseous phase, at T = 298.15 K, as (470.8 +- 1.2) kJ mol 1.

Compounds

#	Formula	Name
1	CO2	carbon dioxide
2	N2	nitrogen
3	H2O	water
4	O2	oxygen
5	C3H2N2O3	parabanic acid

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Constraint	Phase	Method	#Points
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DSC	1
POMD	5	Triple point temperature, K ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DTA	1
POMD	5	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	5	Triple point temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	5	Molar heat capacity at constant pressure, J/K/mol ; Crystal 3	Temperature, K; Crystal 3	Pressure, kPa; Crystal 3	Crystal 3	Small sample (50 mg) DSC	26
POMD	5	Molar heat capacity at constant pressure, J/K/mol ; Crystal 2	Temperature, K; Crystal 2	Pressure, kPa; Crystal 2	Crystal 2	Small sample (50 mg) DSC	16
POMD	5	Vapor or sublimation pressure, kPa ; Crystal 3	Temperature, K; Crystal 3		Crystal 3 Gas	Calculated from knudsen effusion weight loss	16
POMD	5	Vapor or sublimation pressure, kPa ; Crystal 2	Temperature, K; Crystal 2		Crystal 2 Gas	Calculated from knudsen effusion weight loss	13
RXND	5 1 2 3 4	Specific internal energy of reaction at constant volume, J/g				Static bomb calorimetry	1

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Structural studies of cyclic ureas: 2. Enthalpy of formation of parabanic acid

Ribeiro da Silva, M. D. M. C.[Maria D. M. C.], Ribeiro da Silva, M. A. V.[Manuel A. V.], Freitas, V. L. S.[Vera L.S.], Roux, M. V.[MarIa Victoria], Jimenez, P.[Pilar], Davalos, J. Z.[Juan Z.], Cabildo, Pilar, Claramunt, R. M.[Rosa M.], Elguero, J.[Jose]

ABSTRACT