ABSTRACT

The standard (po = 0.1 MPa) molar enthalpies of formation in the condensed phase, DfHo m, of 2,4-dichloro- 5-methylpyrimidine, 2,4-dichloro-6-methylpyrimidine, 4,6-dichloro-2-methylpyrimidine and 4,6- dichloro-5-methylpyrimidine were derived from the standard molar energies of combustion, DcUo m, in oxygen, to yield CO2 (g), N2 (g) and HCl 600H2O (l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation, Dg cr;lHo m, for these compounds, at T = 298.15 K were determined by high temperature Calvet microcalorimetry. Combining these values, the following enthalpies of formation in the gas phase, at T = 298.15 K, were then derived: 2,4-dichloro-5-methylpyrimidine, (79.6 +- 4.1) kJ mol 1, 2,4-dichloro-6-methylpyrimidine, (70.5 +- 3.0) kJ mol 1, 4,6-dichloro-2-methylpyrimidine, (68.7 +- 3.3) kJ mol 1, and 4,6-dichloro-5-methylpyrimidine, (78.1 +- 2.5) kJ mol 1. The gas-phase enthalpies of formation were also estimated by G3 theoretical calculations, which were extended to the computation of gas-phase enthalpies of formation of the other dichloromethylpyrimidine isomers, namely, 2,5-dichloro-4-methylpyrimidine, 4,5-dichloro-2- methylpyrimidine and 4,5-dichloro-6-methylpyrimidine, whose experimental study was not performed.

Compounds

#	Formula	Name
1	ClH	hydrogen chloride
2	CO2	carbon dioxide
3	N2	nitrogen
4	H2O	water
5	O2	oxygen
6	C5H4Cl2N2	2,4-dichloro-5-methylpyrimidine
7	C5H4Cl2N2	2,4-dichloro-6-methylpyrimidine
8	C5H4Cl2N2	4,6-dichloro-2-methylpyrimidine
9	C5H4Cl2N2	4,6-dichloro-5-methylpyrimidine

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	Phase	Method	#Points
POMD	6	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid	Liquid Gas	Static calorimetry	1
POMD	6	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Crystal	Drop calorimetry	1
POMD	7	Molar enthalpy of vaporization or sublimation, kJ/mol ; Crystal	Temperature, K; Crystal	Crystal Gas	Static calorimetry	1
POMD	7	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Crystal	Drop calorimetry	1
POMD	8	Molar enthalpy of vaporization or sublimation, kJ/mol ; Crystal	Temperature, K; Crystal	Crystal Gas	Static calorimetry	1
POMD	8	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Crystal	Drop calorimetry	1
POMD	9	Molar enthalpy of vaporization or sublimation, kJ/mol ; Crystal	Temperature, K; Crystal	Crystal Gas	Static calorimetry	1
POMD	9	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Crystal	Drop calorimetry	1
RXND	6 1 2 3 4 5	Specific internal energy of reaction at constant volume, J/g			Rotating bomb calorimetry	1
RXND	7 1 2 3 4 5	Specific internal energy of reaction at constant volume, J/g			Rotating bomb calorimetry	1
RXND	8 1 2 3 4 5	Specific internal energy of reaction at constant volume, J/g			Rotating bomb calorimetry	1
RXND	9 1 2 3 4 5	Specific internal energy of reaction at constant volume, J/g			Rotating bomb calorimetry	1

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Thermochemical study of dichloromethylpyrimidine isomers

Szterner, P.[Piotr], Amaral, L. M. P. F.[Luisa M.P.F.], Morais, V. M. F.[Victor M.F.], Ribeiro da Silva, M. D. M. C.[Maria D.M.C.], Ribeiro da Silva, M. A. V.[Manuel A.V.]

ABSTRACT