Nearest-Neighbor and Non-Nearest-Neighbor Interactions between Substituents in the Benzene Ring. Experimental and Theoretical Study of Functionally Substituted Benzamides

Standard molar enthalpies of formation of 2- and 4-hydroxy­benz­amides were measured by combustion calorimetry. Vapor pressures of benz­amide and 2-hydroxy­benz­amide were derived by the transpiration method. Standard molar enthalpies of sublimation or vaporization of these compounds at 298 K were obtained from vapor pressure temperature dependence. Thermochemical data on benz­amides with hydroxyl, methyl, methoxy, amino, and amide substituents were collected, evaluated, and tested for internal consistency. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas-phase enthalpies of formation. Sets of nearest-neighbor and non-nearest-neighbor interactions between substituents in the benzene ring have been evaluated. A simple incremental procedure has been suggested for a quick appraisal of the vaporization and gas-phase formation enthalpies of the substituted benz­amides

Benchmark Thermodynamic Properties of Methyl- and Methoxybenzamides: Comprehensive Experimental and Theoretical Study

The enthalpies of formation of 2-, 3-, and 4-CH₃-benzamide, as well as for 2-CH₃O-benzamide, were measured by using combustion calorimetry. Vapor pressures of the isomeric CH₃- and CH₃O-benzamides were measured by using the transpiration method. The enthalpies of sublimation/vaporization of these compounds at 298 K were obtained from temperature dependencies of vapor pressures. The enthalpies of solution of the isomeric CH₃- and CH₃O-benzamides were measured with solution calorimetry. The enthalpies of sublimation of m- and p-substituted benzamides were independently derived with help of a solution calorimetry-based procedure. The enthalpies of fusion of the CH₃-benzamides were derived from differential scanning calorimetry measurements. Thermochemical data on CH₃- and CH₃O-benzamides were collected, evaluated, and tested for internal consistency. A simple incremental procedure was suggested for a quick appraisal of vaporization enthalpies of substituted benzamides. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas-phase enthalpies of formation. A remarkable ability of the G4-based atomization procedure to calculate reliable enthalpies of formation was established for the set of aliphatic and aromatic amides. An outlook for the proper validation of the G4-AT procedure was discussed

Thermochemical Properties of Phase Transitions and Solvation for Some Mono- and Di-cyanate Esters at 298.15 K

We have obtained the thermochemical properties of the phase transition of six mono- and di-cyanate esters for the first time. Vapor pressure–temperature dependences and enthalpies of vaporization for two mono-cyanate esters were measured by fast scanning calorimetry and transpiration method. Fusion enthalpies of cyanate esters were studied by differential scanning calorimetry. We have developed an additive scheme for the evaluation of solvation enthalpies of cyanate esters based on the reliable data of solution and sublimation enthalpies of one mono-cyanate ester. The proposed scheme and experimental solution enthalpies in different solvents were further used for the determination of the vaporization and sublimation enthalpies of other cyanate esters at 298.15 K