Title
Structural studies of cyclic ureas: 2. Enthalpy of formation of parabanic acid
Date Issued
01 September 2008
Access level
metadata only access
Resource Type
journal article
Author(s)
Ribeiro da Silva M.d.D.M.C.
Ribeiro da Silva M.A.V.
Freitas V.L.S.
Roux M.V.
Jiménez P.
Cabildo P.
Claramunt R.M.
Elguero J.
Consejo Superior de Investigaciones Científicas
Abstract
Thermophysical and thermochemical studies have been carried out for crystalline parabanic acid. The thermophysical study was made by differential scanning calorimetry, DSC, over the temperature interval between T = (263 and 473) K. Two phase transitions were found: at T = (392.3 ± 1.6) K with the enthalpy of transition of (2.1 ± 0.4) kJ · mol-1 and at T = (509.8 ± 1.5) K, when the compound was scanned to its fusion temperature. The standard (p{ring operator} = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, for crystalline parabanic acid was determined using static-bomb combustion calorimetry as -(590.2 ± 1.0) kJ · mol-1. The standard molar enthalpy of sublimation, at T = 298.15 K, was derived from the variation of their vapour pressures, measured by the Knudsen-effusion method, with the temperature. These two thermochemical parameters yielded the standard molar enthalpy of formation in the gaseous phase, at T = 298.15 K, as -(470.8 ± 1.2) kJ · mol-1. © 2008 Elsevier Ltd. All rights reserved.
Start page
1378
End page
1385
Volume
40
Issue
9
Language
English
OCDE Knowledge area
Química
Subjects
Scopus EID
2-s2.0-49049099372
Source
Journal of Chemical Thermodynamics
ISSN of the container
10963626
Sponsor(s)
Thanks are due to Gabinete de Relações Internacionais da Ciência e do Ensino Superior (GRICES), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı´ficas (CSIC), Madrid, Spain for a joint research project GRICES/CSIC. Thanks are due to Fundação para a Ciência e a Tecnologia, F.C.T., Lisbon, Portugal, and to FEDER for financial support to Centro de Investigação em Quı´mica da Universidade do Porto (CIQ-U.P.). V.L.S.F. thanks Faculdade de Ciências for a research grant. The Spanish co-authors gratefully acknowledged the support of DGES/MEC (CTQ 2006-02586, CTQ 2006-12745/BQU, CTQ 2006-10178/BQU, CTQ 2007-60895/BQU) and to Prof. Ibon Alkorta for his help.
Sources of information:
Directorio de Producción Científica
Scopus