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

Abstract

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 298K 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.