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- Title
Energetic and structural characterization of 2-R-3-methylquinoxaline-1,4-dioxides (R = benzoyl or tert-butoxycarbonyl): experimental and computational studies.
- Authors
Gomes, José R. B.; Sousa, Emanuel A.; Gonçalves, Jorge M.; Gales, Luís; Damas, Ana M.; Gomes, Paula; Pandey, Siddharth; Acree Jr., William E.; Ribeiro da Silva, Maria D. M. C.
- Abstract
The gaseous standard molar enthalpies of formation of two 2-R-3-methylquinoxaline-1,4-dioxides (R = benzoyl or tert-butoxycarbonyl), at T = 298.15 K, were derived using the values for the enthalpies of formation of the compounds in the condensed phase, measured by static bomb combustion calorimetry, and for the enthalpies of sublimation, measured by Knudsen effusion, using a quartz crystal oscillator. The three dimensional structure of 2-tert-butoxycarbonyl-3-methylquinoxaline-1,4-dioxide has been obtained by X-ray crystallography showing that the two N&bond;O bond lengths in this compound are identical. The experimentally determined geometry in the crystal is similar to that obtained in the gas-phase after computations performed at the B3LYP/6-311 + G(2d,2p) level of theory. The experimental and computational results reported allow to extend the discussion about the influence of the molecular structure on the dissociation enthalpy of the N&bond;O bonds for quinoxaline 1,4-dioxide derivatives. As found previously, similar N&bond;O bond lengths in quinoxaline-1,4-dioxide compounds are not linked with N&bond;O bonds having the same strength. Copyright © 2007 John Wiley & Sons, Ltd.
- Subjects
ENTHALPY; MOLECULAR structure; CRYSTALLOGRAPHY; THERMODYNAMICS; TEMPERATURE measurements
- Publication
Journal of Physical Organic Chemistry, 2007, Vol 20, Issue 7, p491
- ISSN
0894-3230
- Publication type
Article
- DOI
10.1002/poc.1184