The standard (p = 0.1 MPa) molar enthalpy of combustion, DcH m, of two crystalline compounds, 5,6- dihydro-5-methyluracil and 5,6-dihydro-6-methyluracil, were determined, at T = 298.15 K, using a static bomb combustion calorimeter. The vapor pressures as a function of the temperature were measured for those compounds, by the Knudsen effusion technique, and the standard molar enthalpies of sublimation at the mean temperature of the vapor pressure measurements were derived from the Clausius Clapeyron equation, and corrected to T = 298.15 K using an estimated value for deltagcr C p;m. These values were used to derive the standard molar enthalpies of formation of the two compounds studied, in the condensed and gaseous phases. Some considerations about the relative stability of the two isomers were made and compared with similar compounds.
Compounds
#
Formula
Name
1
CO2
carbon dioxide
2
N2
nitrogen
3
H2O
water
4
O2
oxygen
5
C5H8N2O2
5,6-dihydro-5-methyluracil
6
C5H8N2O2
5,6-dihydro-6-methyluracil
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
Vapor or sublimation pressure, kPa ; Crystal
Temperature, K; Crystal
Crystal
Gas
Calculated from knudsen effusion weight loss
36
POMD
6
Vapor or sublimation pressure, kPa ; Crystal
Temperature, K; Crystal
Crystal
Gas
Calculated from knudsen effusion weight loss
35
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