ABSTRACT

A thermophysical and thermochemical study has been carried out for crystalline imidazolidin-2-one and N,N0-trimethyleneurea [tetrahydropyrimidin- 2(1H)-one]. The thermophysical study was made by differential scanning calorimetry, d.s.c., in the temperature intervals between T = 268 K and their respective melting temperatures. Several solid solid transitions have been detected in imidazolidin-2- one. The standard (p = 0.1 MPa) molar enthalpies of formation, at T = 298.15 K, for crystalline imidazolidin-2-one and N,N0-trimethyleneurea [tetrahydropyrimidin-2(1H)-one], were determined using static-bomb combustion calorimetry. The standard molar enthalpies of sublimation, at T = 298.15 K, for the two compounds were 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 enthalpies of formation of the two cyclic urea compounds studied in the gaseous phase at T = 298.15 K. These values are discussed in terms of molecular structural contributions and interpreted on the bases of the benzo-condensed effect and of the ring strain of imidazolidin-2-one.

Compounds

#	Formula	Name
1	CO2	carbon dioxide
2	N2	nitrogen
3	H2O	water
4	O2	oxygen
5	C3H6N2O	2-imidazolidinone
6	C4H8N2O	tetrahydropyrimidin-2(1H)-one

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 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	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 2	Temperature, K; Crystal 2	Pressure, kPa; Crystal 2	Crystal 2	Small sample (50 mg) DSC	17
POMD	5	Vapor or sublimation pressure, kPa ; Crystal 2	Temperature, K; Crystal 2		Crystal 2 Gas	Calculated from knudsen effusion weight loss	29
POMD	5	Vapor or sublimation pressure, kPa ; Crystal 1	Temperature, K; Crystal 1		Crystal 1 Gas	Calculated from knudsen effusion weight loss	6
POMD	6	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Small sample (50 mg) DSC	43
POMD	6	Vapor or sublimation pressure, kPa ; Crystal	Temperature, K; Crystal		Crystal Gas	Calculated from knudsen effusion weight loss	31
RXND	5 1 2 3 4	Specific internal energy of reaction at constant volume, J/g				Static bomb calorimetry	1
RXND	6 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: 1. Enthalpies of formation of imidazolidin-2-one and N,N0-trimethyleneurea

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], Temprado, M.[Manuel], Davalos, J. Z.[Juan Z.], Cabildo, Pilar, Claramunt, R. M.[Rosa M.], Elguero, J.[Jose]

ABSTRACT