Estudos cineticos das reações de PAR com Zn2+ e Cu2+ e estudos de espectroscopia de ATR de soluções aquosas de sais

AUTOR(ES)

Adriana Vitorino Rossi

DATA DE PUBLICAÇÃO

1995

RESUMO

Spectroscopic and kinetic studies were developed to investigate the effect of organization of aqueous solutions in chemical reactions. Total internal reflection spectroscopy were applied to perform infrared spectra using a Nicolet 520-FTIR spectrometer and a micro CIRCLE® cell with ZnSe rod. Infrared spectra of the following species were studied: H2O and HDO at various temperatures, 0.9135 mol/L aqueous solutions of alkaline and earth alkaline chlorides, 1.00 mol/l aqueous solutions of MgCI2, MgSO4, NaCI CuCI2, ZnCI2, 0.50mol/L aqueous solutions of Na2SO4, and 0.02 to 1.02 mol/L aqueous solutions of CuSO4 e ZnSO4. The spectral data show that two different class of water molecules can be proposed, according of their agregation level in liquid state: "free water" and "bond water". The temperature changes the agregation of water molecules in liquid state, changing the populations of these classes. The ions also modifies the agregation, cations create a new class of water molecules that interacts directly with them. All these interactions can be responsable for some chemical behavior. The kinetic of reactions of complexation of PAR with Cu, Zn and Cu+Zn mixtures were studied using stopped-flow technique. The instrument were built in our laboratory with some old device and a interface to a IBM/PC-386 compatible microcomputer. The reactions were monitored spectrophotometrically at 500 nm and 25.00.1°C. This complexation is a second order reaction, first order with respect to PAR and metallic cation concentrations. The equimolar mixtures of Cu and Zn have a proper konstant. The interactions of the ions and the water molecules of the solutions on the organizational structure can be contributing for this unusual behavior. The reactions should be more easily understood considering solvated ions groups. In this case, different cations of a mixture can form a solvated ion group with proper characteristics, even chemical kinetics. The interactions among the species in aqueous solutions are detectable by infrared measurements. The kinetics of mixtures complexation seems to reflect the effect of these interactions. This can be used as a model to help understand the effects of various cations present in important metabolic processes, when complexes take part.

ASSUNTO(S)

soluções(quimica) analise espectral reações quimicas cinetica quimica

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