Thermochemical Studies on 3-Methyl-quinoxaline-2-carboxamide-1,4-dioxide Derivatives: Enthalpies of Formation and of N−O Bond Dissociation

• DOI: 10.1021/jp067818c
• Publication Date: 2007-02-04T01:50:00Z
• Authors: José R. B. Gomes; Emanuel A. Sousa; Paula Gomes; Nuno Vale; Jorge M. Gonçalves; Siddharth Pandey; William E. Acree,; Maria D. M. C. Ri...
• Keywords: Sublimation; Bond-dissociation energy; Enthalpy of sublimation

The standard molar enthalpies of formation the 3-methyl-N-R-2-quinoxalinecarboxamide-1,4-dioxides (R = H, phenyl, 2-tolyl) in gas phase were derived using values for combustion crystalline compounds, measured by static bomb calorimetry, and sublimation, Knudsen effusion, at T 298.15 K. These have also been used to calibrate a computational procedure that has employed estimate gas-phase corresponding 3-methyl-N-R-2-quinoxalinecarboxamides compute first, second, mean N−O bond dissociation phase. It is found size substituent almost does not influence computed enthalpies; maximum enthalpic difference ∼5 kJ·mol-1.