In the present work, a combined experimental and computational thermochemical study of nitroimidazole isomers was carried out. The standard (p = 0.1 MPa) molar enthalpy of combustion, in the crystalline phase, for 4-nitroimidazole was determined, at the temperature of 298.15 K, using a static bomb combustion calorimeter. Calvet microcalorimetry experiments were performed to measure its standard molar enthalpy of sublimation. The standard molar enthalpy of formation of 4-nitroimidazole, in the gaseous phase, at T = 298.15 K, (116.9 +- 2.9) kJ mol-1, has been derived from the corresponding standard molar enthalpy of formation in the crystalline phase and the standard molar enthalpy of sublimation. Computational studies for 4-nitroimidazole were performed to complement the experimental work. These were also extended to the 2- and 5-nitroimidazole isomers. The gas-phase enthalpies of formation were estimated from high level ab initio molecular orbital calculations, at the G3 level. Also investigated were the tautomeric equilibrium of 4(5)-nitroimidazole in the gaseous phase and it was concluded that the two tautomers are equally stable.
Compounds
#
Formula
Name
1
CO2
carbon dioxide
2
N2
nitrogen
3
H2O
water
4
O2
oxygen
5
C3H3N3O2
4-nitroimidazole
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 vaporization or sublimation, kJ/mol ; Crystal
Temperature, K; Crystal
Crystal
Gas
Static calorimetry
1
POMD
5
Molar enthalpy, kJ/mol ; Gas
Temperature, K; Gas
Gas
Crystal
Drop calorimetry
1
RXND
5
1
2
3
4
Specific internal energy of reaction at constant volume, J/g