The enthalpies of dissociation of the N-O bonds in two quinoxaline derivatives


The present work reports the first experimental thermochemical study of mono-N-oxides derived from quinoxaline, namely, 3-methoxycarbonyl-2-methyl-quinoxaline N-oxide and 3-ethoxycarbonyl-2-methyl-quinoxaline N-oxide. The values of the enthalpies of formation, in the condensed state, and of the enthalpies of sublimation, derived from static bomb calorimetry and Calvet microcalorimetry measurements, respectively, are combined to derive the standard molar enthalpies of formation in the gaseous phase for these two compounds. From the latter values, the first and second N-O bond dissociation enthalpies for the corresponding di-N-oxides have been obtained. The gas-phase experimental results are also compared with calculated data obtained with a density functional theory approach. Copyright (c) 2008 John Wiley & Sons, Ltd.



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Gomes, JRB; Monteiro, AR; Campos, BB; Gomes, P; da Silva, MDMCR

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Thanks are due to FCT and to FEDER for financial support to the research project (POCTI/44471/QUI/2002). J.R.B.G. and A.R.M. thank FCT for the award of their research scholarships. Thanks are also due to the University of Porto for funding through the program 'Investigacao Cientifica na Pregraduacao and supported by Caixa Geral de Depositos.

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