The standard (p? = 0.1 MPa) molar energy of combustion, at T = 298.15 K, of crystalline 2,3-dicyanopyrazine was measured by static bomb calorimetry, in oxygen atmosphere. The standard molar enthalpy of sublimation, at T = 298.15 K, was obtained by Calvet Microcalorimetry, allowing the calculation of the standard molar enthalpy of formation of the compound, in the gas phase, at T = 298.15 K: DfH?m (g) = (518.7 +- 3.4) kJ Ae mol?1. In addition, the geometries of all cyanopyrazines were obtained using density functional theory with the B3LYP functional and two basis sets: 6-31G* and 6-311G**. These calculations were then used for a better understanding of the relation between structure and energetics of the cyanopyrazine systems. These calculations also reproduce measured standard molar enthalpies of formation with some accuracy and do provide estimates of this thermochemical parameter for those compounds that could not be studied experimentally, namely the tri- and tetracyanopyrazines: the strong electron withdrawing cyano group on the pyrazine ring makes cyanopyrazines highly destabilized compounds.
Compounds
#
Formula
Name
1
CO2
carbon dioxide
2
N2
nitrogen
3
H2O
water
4
O2
oxygen
5
C6H2N4
2,3-pyrazinedicarbonitrile
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
Crystal
Liquid
Air at 1 atmosphere
DSC
1
POMD
5
Triple point temperature, K ; Crystal
Crystal
Liquid
Air at 1 atmosphere
DTA
1
POMD
5
Mass density, kg/m3 ; Crystal
Temperature, K; Crystal
Pressure, kPa; Crystal
Crystal
Estimation
1
RXND
5
1
2
3
4
Specific internal energy of reaction at constant volume, J/g