Thermochemical study of three dibromophenol isomers

• Type: Article in International Scientific Journal
• Date: 2011

Authors

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

Journal

Title: Journal of Chemical Thermodynamics

Vol. 43

Pages: 227-234

ISSN: 0021-9614

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 6 Citations

Scopus - 4 Citations

Other information

Authenticus ID: 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8