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

Abstract: The thermodynamic properties of 2-pyridinealdoxime were investigated through the thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Low-temperature heat capacity C p,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 [H T − H 298.15] and [S T − S 298.15] were calculated in the range from (80 to 375)K. The constant-volume energy and standard molar enthalpy of combustion have been determined, (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, (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. [Copyright &y& Elsevier]