Low-temperature heat capacity and standard molar enthalpy of formation of crystalline 2-pyridinealdoxime (C6H6N2O)

The thermodynamic properties of 2-pyridinealdoxime were investigated through the thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Low-temperature heat capacity Cp,m of 2-pyridinealdoxime (C6H6N2O; CAS 873-69-8) was measured in the temperature range from (80 to 373) K with a high precision automated adiabatic calorimeter. No phase transition or thermal anomaly was observed in this range. The thermodynamic functions [HT − H298.15] and [ST − S298.15] were calculated in the range from (80 to 375) K. The constant-volume energy and standard molar enthalpy of combustion have been determined, ΔcU(C6H6N2O,cr)=ΔcHm∘ (C6H6N2O, cr) = − (3297.11 ± 1.53) kJ · mol−1 (based on Δn being zero in reaction of the combustion), by means of a precision oxygen-bomb combustion calorimeter at T = (298.15 ± 0.001) K. The standard molar enthalpy of formation has been derived, ΔfHm∘ (C6H6N2O, cr) = (78.56 ± 2.43) kJ · mol−1, from the standard molar enthalpy of combustion in combination with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.