Structural and Thermodynamic Characterization of Polyphenylbenzenes

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

Autores

Carlos F R A C Lima (Autor) Outra; Marisa A A Rocha (Autor) Outra; Andre Melo (Autor) FCUP; Ligia R Gomes (Autor) Outra; John N Low (Autor) Outra; Luis M N B F Santos (Autor) FCUP

Revista

Título: Journal of Physical Chemistry A

Vol. 115

Páginas: 11876-11888

ISSN: 1089-5639

Editora: American Chemical Society

Indexação

ISI Web of Knowledge - 25 Citações

Scopus - 27 Citações

Classificação Científica

FOS: Ciências exactas e naturais > Química

Outras Informações

ID Authenticus: P-002-KEH

DOI: 10.1021/jp207593s

Abstract (EN): The thermodynamic and structural study of a series of polyphenylbenzenes, from benzene, n(Ph) = 0, to hexaphenylbenzene, n(Ph) = 6, is presented. The available literature data for this group of compounds was extended by the determination of the relevant thermodynamic properties for 1,2,4-triphenylbenzene, 1,2,4,5-tetraphenylbenzene, and hexaphenylbenzene, as well as structural determination by X-ray crystallography for some of the studied compounds. Gas phase energetics in this class of compounds was analyzed from the derived standard molar enthalpies of formation in the gaseous phase. The torsional profiles relative to the phenyl-phenyl hindered rotations in some selected polyphenylbenzenes, as well as the gas phase structures and energetics, were derived from quantum chemical calculations. In the ideal gas phase, a significant enthalpic destabilization was observed in hexaphenylbenzene relative to the other polyphenylbenzenes, due to steric crowding between the six phenyl substituents. A relatively low enthalpy of sublimation was observed for hexaphenylbenzene, in agreement with the decreased surface area able to establish intermolecular interactions. The apparently anomalous low entropy of sublimation observed for hexaphenylbenzene is explained by its high molecular symmetry and the six highly hindered phenyl internal rotations. For the series of polyphenylbenzenes considered, it was shown that the differentiation in the entropy of sublimation can be chiefly ascribed to the torsional freedom of the phenyl substituents in the gas phase and the entropy terms related with molecular symmetry.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 13