Sintese, caracterização e termoquimica de adultos envolvendo trialetos de arsenico com amidas e ticamidas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1989

RESUMO

Adducts AsX3.nL (X = CI, Br or l; L = TMTU, DMTA, DMTF, TU, TA, DMA, or A; n =1 or 2) were isolated and characterized by elemental analysis, melting point determination, thermogravimetri, analysis, infrared spectroscopy and mass spectrometry. All adducts decompose on heating. The mass spectra of adducts showed only the fragmentations of ligands and trihalides of arsenic. The infrared data showed the coordination af ligands to the arsenic atam through the oxygen atam of the carbonyl group in the case of amides and through the sulfur atom of the thiocarbonyl group in the case of the thioamides. On the base of infrared spectra of the adducts in the low frequencies region, it is proposed the trigonal bipyramidal structure for AsCl3.L and . AsBr3.L adducts. The standard enthalpies of dissolution of the adducts, arsenic trihalides and ligands, in several solvents, were determined and, by means of thermochemical cycles, the standard enthalpies for the following processes were calculated: AsX3(s,l) + nL(s,l) = AsX3.nL(s), DrH AsX3.nL(s) = AsX3(s,l) + nL(g), DDH AsX3(g) + nL(g) = AsX3.nL(s), DMH The standard enthalpies of formation of adducts (DfH ) were also calculated and, the medium energy of arsenic-oxygen (D(As-O)) or arsenic-sulfur (D(As-S)) bonds were estimated. The thermochemical data allow the conclusion of the acidity order AsCI3>AsBr3>AsI3 and the general basicity order DMTF>TATMTU>DMA>A>DMTA>TU.Correlations between several thermochemical parameters and between thermochemical parameters and the kind of the donation atom, the substitution of atoms of hydrogen by methyl groups in the ligands, etc., are established.

ASSUNTO(S)

termoquimica solução (quimica)

ACESSO AO ARTIGO

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