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An Experimental And Theoretical Study Of The Complexation Mechanism Of Al(III) With 2-Hydroxy-4-Methoxy-Benzophenone

Sonia E.Blanco, Mar�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?­a C.Almandoz, Matias I.Sancho

The complexation reaction between AlCl3 and 2(OH)4(OCH3)-benzophenone was investigated by theoretical and experimental procedures, with the purpose of providing further information that supports the recently proposed reaction mechanism for the complexation of 2(OH)- benzophenone with AlCl3. The kinetic experiments were carried out by means of UV-visible spectroscopy varying the temperature (15-30 C), ionic strength (5.37x10-4-1.05x10-2 mol/l) and permittivity (24.55 and 32.63) of the reaction medium. In the theoretical study, thermodynamic magnitudes, torsional angles, length bonds, energy and reactivity indices were used. The calculations were performed by means of the B3LYP/6-31G(d) method and using the PCM model. The specific reaction rate increased when permittivity was decreased and decreased when the ionic strength of the reaction medium was increased. The kinetic results obtained permitted to confirm a three-step reaction mechanism that contemplates the acid-base dissociation of 2(OH)4 (OCH3)-benzophenone, the reaction between AlCl3 and a solvated proton to form the AlCl2 + cation, and the ionic reaction between the anion of benzophenone and the metal cation. This reaction between two ions of opposite charges is the rate-determining step of the complexation reaction analyzed. On the other hand, the magnitudes theoretical are in good agreement with the experimental data.