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Author(s): Manuel A V R Ribeiro da Silva
Luis M N B F Santos
Luis Spencer S S Lima
Title: Thermodynamic study of 1,2,3-triphenylbenzene and 1,3,5-triphenylbenzene
Issue Date: 2010
Abstract: The energetic study of 1,2,3-triphenylbenzene (1.2,3-TPhB) and 1,3,5 -triphenylbenzene (1,3,5-TPhB) isomers was carried out by making use of the mini-bomb combustion calorimetry and Knudsen mass-loss effusion techniques. The mini-bomb combustion calorimetry technique was used to derive the standard (p degrees = 0.1 MPa) molar enthalpies of formation in the crystalline state from the measured standard molar energies of combustion for both isomers. The Knudsen mass-loss effusion technique was used to measure the dependence with the temperature of the vapour pressure of crystalline 1.2.3-TPhB, which allowed the derivation of the standard molar enthalpy of sublimation, by application of the Clausius-Clapeyron equation. The sublimation study of 1,3,5-TPhB had been performed previously. From the combination of data obtained by both techniques, the standard molar enthalpies of formation in the gaseous state, for both isomers. at T = 298.15 K, were calculated. The results indicate a higher stability of the 1,3,5-TPhB isomer relative to 1,2,3-TPhB, similarly to the terphenyls. Nevertheless, the 1,2,3-TPhB isomer is not as energetically destabilized as one might expect, supporting the existence of a pi-pi displacive stacking interaction between both pairs of outer phenyl rings. The volatility difference between the two isomers is ruled by the enthalpy of sublimation. The volatility of the 1,2,3-TPhB is two orders of magnitude higher than the 1,3,5-TPhB isomer, at T = 298.15 K. [GRAPHICS]
Subject: Engenharia mecânica
Mechanical engineering
Scientific areas: Ciências da engenharia e tecnologias::Engenharia mecânica
Engineering and technology::Mechanical engineering
Document Type: Artigo em Revista Científica Internacional
Rights: restrictedAccess
Appears in Collections:FCUP - Artigo em Revista Científica Internacional

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