What is the enthalpy of formation of pyrazine-2-carboxylic acid?

Abstract

There are two contemporary conflicting, indeed, incompatible determinations of measurements of the enthalpies of combustion and of formation of pyrazine-2-carboxylic acid in the literature, ( 2268.0 ± 0.9 and 271.2 ± 1.1 kJ mol 1) and ( 2211.4 ± 0.9 and 327.8 ± 1.1 kJ mol 1). The current paper discusses these two sets of values and from the use of a measurement of the enthalpy of sublimation, a newly evaluated enthalpy of formation of pyrazine itself, and of the quantum chemical calculations at the G3(MP2)//B3LYP level, the former results are accepted and the derived gas phase enthalpy of formation, (167.6 ± 3.1) kJ mol 1, suggested.