Benchmark properties of 2-, 3- and 4-nitrotoluene: Evaluation of thermochemical data with complementary experimental and computational methods

Abstract

Thermochemical properties of nitrotoluenes are in disarray. New standard (p=0.1MPa) molar enthalpies of formation at the temperature T=298.15K of the liquid 3-nitrotoluene and crystalline 4-nitrotoluene were measured using high-precision combustion calorimetry. New molar enthalpies of vaporization of 2-, 3-, and 4-nitrotoluene were derived from the vapour pressure temperature dependence measured by the transpiration method. Thermodynamic data on nitrotoluenes available in the literature were collected, evaluated, and combined with own experimental results. This collection, together with the new experimental results reported here, has helped to resolve contradictions in the available enthalpies of formation data and to recommend the set of vaporization and formation enthalpies for 2-, 3-, and 4-nitrotoluene as the reliable benchmark properties for further thermochemical calculations. Gas phase molar enthalpies of formation of 2-, 3-, and 4-nitrotoluene, calculated by high-level quantum-chemical method G4, were found in a good agreement with the recommended experimental data.