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

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• 作者：Jos&eacute ; R. B. Gomes ; Emanuel A. Sousa ; Paula Gomes ; Nuno Vale ; Jorge M. Gon&ccedil ; alves ; Siddharth Pandey ; William E. Acree ; Jr. ; Maria D. M. C. Ribeiro da Silva
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：March 1, 2007
• 年：2007
• 卷：111
• 期：8
• 页码：2075 - 2080
• 全文大小：98K
• 年卷期：v.111,no.8(March 1, 2007)
• ISSN：1520-5207

文摘

The standard molar enthalpies of formation of the 3-methyl-N-R-2-quinoxalinecarboxamide-1,4-dioxides(R = H, phenyl, 2-tolyl) in the gas phase were derived using the values for the enthalpies of combustion ofthe crystalline compounds, measured by static bomb combustion calorimetry, and for the enthalpies ofsublimation, measured by Knudsen effusion, at T = 298.15 K. These values have also been used to calibratea computational procedure that has been employed to estimate the gas-phase enthalpies of formation of thecorresponding 3-methyl-N-R-2-quinoxalinecarboxamides and also to compute the first, second, and meanN-O bond dissociation enthalpies in the gas phase. It is found that the size of the substituent almost does notinfluence the computed N-O bond dissociation enthalpies; the maximum enthalpic difference is ~5 kJ·mol^-1.