Thermochemical study of three dibromophenol isomers

• Tipo: Artigo em Revista Científica Internacional
• Data: 2011

Autores

Ana I M C L Lobo Ferreira (Autor) FCUP; da Silva, MAVR (Autor) FCUP

Revista

Título: Journal of Chemical Thermodynamics

Vol. 43

Páginas: 227-234

ISSN: 0021-9614

Editora: Elsevier

Indexação

ISI Web of Knowledge - 6 Citações

Scopus - 4 Citações

Outras Informações

ID Authenticus: P-002-TZ8

DOI: 10.1016/j.jct.2010.08.020

Abstract (EN): This work reports the standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, Delta(f)H degrees(m)(g), of 2,4-, 2,6-, and 3,5-dibromophenol, at T = 298.15 K, respectively, as (59.6 +/- 2.6) kJ . mol(-1), (49.1 +/- 2.2) kJ . mol(-1) and (39.5 +/- 2.0) kJ . mol(-1). These experimental values were derived from the measurements of the standard molar enthalpies of formation, in the crystalline phase, Delta(f)H degrees(m), (2, 4-dibromophenol, Cr) = -(140.9 +/- 2.1) kJ . mol(-1), Delta(f)H degrees(m) (2, 6-dibromophenol, cr) = -(132.5 +/- 1.6) kJ . mol(-1) and Delta fH degrees(m) (3, 5-dibromophenol, cr) = -(134.5 +/- 1.7) kJ . mol(-1), at the same reference temperature, achieved from the standard molar enthalpies of combustion, in oxygen, to yield CO(2)(g) and HBr.600H(2)O(I), measured by rotating-bomb combustion calorimetry, together with measurements of the standard molar enthalpies of sublimation, at T = 298.15 K, as Delta(g)(cr)H degrees(m) (2, 4-dibromophenol) = (81.3 +/- 1.5) kJ . mol(-1), Delta(g)(cr)H degrees(m) (2, 6-dibromophenol) = (83.4 +/- 1.5) kJ . mol(-1) and Delta(g)(cr)H degrees(m) (3, 5-dibromophenol) (94.3 +/- 1.8) kJ . mol(-1), obtained using the Calvet high temperature vacuum sublimation technique. The standard molar enthalpy of sublimation, at T = 298.15 K, for the 3,5-dibromophenol was also determined from the temperature-vapour pressure dependence, obtained by the Knudsen mass loss effusion method, Delta(g)(cr)H degrees(m) (3.5-dibromophenol) = (95.0 +/- 1.1) kJ . mol(-1). For this isomer it is also reported the standard (p degrees = 0.1 MPa) molar entropy and Gibbs energy of sublimation, at T = 298.15 K. The experimental values of the gas-phase enthalpies of formation of each compound were compared with estimates using the empirical scheme developed by Cox and with the calculated values based on density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional at the 6-311++G(d,p) basis set. These two methodologies were also used to estimate the enthalpies of formation in the gas-phase of the 2,3-, 2,5-, and 3,4-dibromophenol.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 8