Investigation Of Chlorine Dioxide Chemical Oscillatory Reaction

This paper investigated the C102-I2-methyl acetoacetate (MAA) and ClO2-I-methyl acetoacetate (MAA) chemical oscillatory reaction systems by UV-vis spectrophotometric method and online infrared spectrum. The reaction of I2-MAA was also studied by online infrared spectrum.In the system of ClO2-I2-MAA, the induced period can not be observed at296nm without adding starch, while the reaction has an induced period at460nm and581nm by adding starch. The oscillation phenomenon is much more obvious by adding starch than that observed without adding starch. It was observed that the number of oscillations increases with the initial concentrations of chlorine dioxide or iodine. The number of oscillations decreases, and the amplitude increases, as the initial concentration of methyl acetoacetate increases or the pH value of the solution increases. Both the induction period and the oscillation period decrease with increasing of reaction temperature, the oscillation reaction can be accelerated by increasing reaction temperature. The apparent activation energies in terms of the induction period and the oscillation period, which were calculated according to Arrhenius equation, are relatively small. The equations for the triiodide ion reaction rate changing with reaction time and the initial concentrations in the oscillation stage were obtained by differentiating and curve fitting of the oscillatory curves which were got in the experiments. The equations of the amplitude and the period of oscillation changing with initial concentrations of various substances were also obtained.In the system of ClO2-I--MAA, the oscillatory reactions at289nm without adding starch and351nm,462nm by adding starch were studied. The induced period can be observed obviously at the three wavelengths, and the induced time can last for about50seconds. It was observed that the number of oscillations increases and the amplitude decreases with the initial concentrations of chlorine dioxide or iodide, while an opposite phenomenon appeared as increasing methyl acetoacetate concentration. As the pH value of the solution increases, the number of oscillations decreases, and the equilibrium time was significantly shortened. Both the induction period and the oscillation period decrease with increasing of reaction temperature. The oscillation life was shortened by increasing temperature. The apparent activation energies in terms of the induction period and the oscillation period, which were calculated according to Arrhenius equation, are relatively small. The equations for the triiodide ion reaction rate changing with reaction time and the initial concentrations in the oscillation stage were obtained by differentiating and curve fitting of the oscillatory curves which were got in the experiments. The equations of the amplitude and the period of oscillation changing with initial concentrations of various substances were also obtained.The reaction of iodine and methyl acetoacetate was investigated by online infrared spectrum analysis. Four intermediates were detected during the reaction. The chemical structures of the four intermediates were identified through the infrared spectrum analysis. The reaction mechanism was proposed based upon the relevant literatures.