Thermodynamic Properties of Quinoxaline-1,4-Dioxide Derivatives: A Combined Experimental and Computational Study
journal contributionposted on 16.04.2004, 00:00 by Maria D. M. C. Ribeiro da Silva, José R. B. Gomes, Jorge M. Gonçalves, Emanuel A. Sousa, Siddharth Pandey, William E. Acree
The mean (N−O) bond dissociation enthalpies were derived for three 2-methyl-3-(R)-quinoxaline 1,4-dioxide (1) derivatives, with R = methyl (1a), ethoxycarbonyl (1b), and benzyl (1c). The standard molar enthalpies of formation in the gaseous state at T = 298.15 K for the three 1 derivatives were determined from the enthalpies of combustion of the crystalline solids and their enthalpies of sublimation. In parallel, accurate density functional theory-based calculations were carried out in order to estimate the gas-phase enthalpies of formation for the corresponding quinoxaline derivatives. Also, theoretical calculations were used to obtain the first and second N−O dissociation enthalpies. These dissociation enthalpies are in excellent agreement with the experimental results herewith reported.