STANDARD MOLAR ENTHALPIES OF FORMATION, VAPOUR PRESSURES, AND ENTHALPIES OF SUBLIMATION OF 2-CHLORO-4-NITROANILINE AND 2-CHLORO-5-NITROANILINE

Manuel A. V. Ribeiro da Silva, Lu�s M. S. S. Lima, Ana I. M. C. L. Ferreira, Jos� R. B. Gomes, Lu�sa M. P. F. Amaral

Centro de Investiga��o em Qu�mica, Department of Chemistry, Faculty of Science, University of Porto, R. Campo Alegre, 687,P-4169-007 Porto, Portugal

  The standard (p0 = 0.1 MPa) molar enthalpies of formation for crystaline 2-chloro-4-nitroaniline and 2-chloro-5-nitroaniline were derived from the standard molar enthalpies of combustion, in oxygen, at T = 298.15 K, measured by rotating bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to measure the vapour pressures of the crystals as function of temperature, and the standrd molar enthalpies of sublimation, at T = 298.15 K were derived by the Clausius-Clapeyron equation. Direct measurements of the standard molar enthalpies of sublimation, using Calvet microcalorimatry for 2-chloro-4-nitroaniline and 2-chloro-5-nitroaniline confirmed the values derived from the Knudsen technique.

Thanks are due to Funda��o para a Ci�ncia e Tecnologia, Lisbon, Portugal (FCT) for financial support to Centro de Investiga��o em Qu�mica, University of Porto and for the award of research grants to L.M.P.F.A. (SRFH/BPD/5595/2001), J.R.B.G. (SRFH/BPD/11582/2002) and A.I.M.C.L.F. (SRFH/BD/6719/2001).