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|Type:||Artigo de periódico|
|Title:||Thermochemistry Of Pyridine- And Picoline-n-oxide Complexes Of Arsenic Trihalides|
|Abstract:||The complexes AsX3·nL (where L = pyridine-N-oxide (pyNO), α, β, or γ-picoline-N-oxide (α, β-, or γ-piCONO), n = 1 or 2 for X = Cl, n = 1, 3/2 or 2 for X = Br and n = 1, 3/2 or 2 for X = I) were prepared and characterised by melting point, elemental analysis, thermogravimetric studies and infrared spectroscopy. From the enthalpies of dissolution in ethanol or 50% 2.4 N HC1 in ethanol of the complexes, arsenic trihalides and ligands at 298.15 K, the standard enthalpies (ΔrHXXX) for the Lewis acid/base reactions were determined. From the ΔrHXXX values, the standard enthalpies of formation of arsenic trihalides and the standard enthalpies of formation of the ligands, the standard enthalpies of formation of the complexes were calculated. The standard enthalpies of decomposition of the complexes (ΔDHXXX), as well as the lattice standard enthalpies (δMHxxx) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (ΔrHXXX(g)), were calculated by means of thermochemical cycles, and the mean standard enthalpies of the arsenic-oxygen bonds (D (As-O)) were estimated. The mean energies of the As-O bonds range from 98 to 125 kJ mol-1 in these complexes. The thennochemical data suggested the order AsCl3 AsBr3 AsI3 for acidity and γ-pi-CONO pyNO ga-piCONO for basicity. Correlation between several of the thennochemical parameters, and between the thennochemical parameters of these complexes and parameters of the complexes of non-oxidized ligands, were established. © 1991.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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