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|Type:||Artigo de periódico|
|Title:||Calorimetric data on n-alkyldiamines intercalated into calcium phenylphosphonates|
|Abstract:||Layered crystalline calcium phenylphosphonate, as anhydrous Ca(HO3PC6H5)(2), and hydrated Ca(HO3PC6H5)(2)center dot 2H(2)O forms were used as hosts for intercalation of n-alkyldiamine molecules H2N(CH2) NHz (n=2-6) in water or 1,2-dichloroethane. The amount intercalated (n(f)) was followed batchwise at 298 +/- 1 K and the variation of the original interlayer distance (d) for hydrated calcium phenylphosphonate (1525 ppm) and anhydrous calcium phenylphosphonate (1751 ppm) was followed by X-ray powder diffraction. Linear correlations were obtained for d or n(f) as a function of the number of carbon atoms in the aliphatic chain (n(c)): d = (1424 +/- 65) + (108 +/- 14)n(c) and n(f) = (3.33 +/- 0.15) - (0.39 +/- 0.03)n(c), for the hydrated compound and d = (1643 +/- 60) + (108 +/- 12)n(c) and n(f) = (3.43 +/- 0.12) - (0.39 +/- 0.01)n(c), for the anhydrous compound. The exothermic enthalpies of intercalation increased with n(c), which derived from the monomolecular amine layer arrangement with longitudinal axis inclined by 58 to the inorganic sheets. The intercalation, followed by titration with amine at the solid/liquid interface with both matrices, gave the enthalpic/number of carbons correlation: Delta H degrees = - (0.54 +/- 0.12) - (1.10 +/- 0.09)n(c) and Delta H degrees = - (1.39 +/- 0.15) - (1.56 +/- 0.10)n(c), respectively. The exothermic enthalpic value increases with n, are more pronounced for the anhydrous compound. The Gibbs free energies are negative while positive entropic values favor intercalation in these systems. (C) 2005 Elsevier B.V. All rights reserved.|
|Editor:||Elsevier Science Bv|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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