Standard molar enthalpies of formation of 1- and 2-cyanonaphthalene

Abstract

The standard ( p° = 0.1 MPa) molar enthalpies of formation, in the crystalline state, of the 1- and 2-cyanonaphthalene were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static-bomb combustion calorimetry. Vapor pressure measurements at different temperatures, using the Knudsen mass loss effusion technique, enabled the determination of the enthalpy, entropy, and Gibbs energy of sublimation, at T = 298.15 K, for both isomers. The standard molar enthalpies of sublimation, at T = 298.15 K, for 1- and 2-cyanonaphthalene, were also measured by high-temperature Calvet microcalorimetry. - Δ c U m ∘ ( cr ) / ( kJ · mol - 1 ) Δ f H m ∘ ( cr ) / ( kJ · mol - 1 ) Δ cr g H m ∘ ( cr ) / ( kJ · mol - 1 ) 1-Cyanonaphthalene 5514.4 ± 1.6 188.5 ± 2.2 88.6 ± 0.5 2-Cyanonaphthalene 5510.5 ± 1.7 184.6 ± 2.2 92.1 ± 0.1 Combining these two experimental values, the gas-phase standard molar enthalpies, at T = 298.15 K, were derived and compared with those estimated by employing two different methodologies: one based on the Cox scheme and the other one based on G3MP2B3 calculations. The calculated values show a good agreement with the experimental values obtained in this work.