Effect of the pH Value on the Rate of the Photoreduction of Methylene Blue by <I>N</I>-Phenylglycines

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概要

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• The effect of the pH value on the rate of the photoreduction of methylene blue by <I>N</I>-phenylglycines was studied in detail in the range between 5.9 and 10.5, attention being paid to the effects of buffer solutions and to a possible change in the ionic species of <I>N</I>-phenylglycines with the change in pH value. <I>N</I>-Phenylglycine behaved as a monobasic acid of p<I>K</I><SUB>a</SUB> 4.3 to base titration, so that it existed solely as a univalent anion C<SUB>6</SUB>H<SUB>5</SUB>NH·CH<SUB>2</SUB>COO-in this pH value range. The p<I>K</I><SUB>a</SUB> of several other <I>N</I>-phenylglycines was given also. The concentration and ionic strength of the buffer solutions had some effect; they must be kept constant and as small as possible.<BR>With these precautions, the pH value dependences of <I>Φ</I><SUB>∞</SUB> , 1/<I>b</I> and <I>B</I>=1/(<I>Φ</I><SUB>∞</SUB>·b), which characterize the quantum yield of the photoreduction, were determined for several electron donors. They were similar in all cases. Semicarbazide was found to be effective as an electron donor for this photoreduction. Log <I>B</I> varied linearly with the pH value in the pH range between 7.0 and 9.0. The slopes were nearly 0.5 for all the <I>N</I>-phenylglycines studied. This means that, if the excited metastable state of the dye formed a complex before the oxidation-reduction reaction, the rate constant of its formation must vary as the root of the hydroxide ion concentration.

• 社団法人 日本化学会の論文

著者

• MATSUMOTO S.

  Faculty of Science and Technology, Keio University

• Matsumoto Shiro

  Faculty of Agriculture Kagawa University

関連論文

• Boron-Induced √×√ Reconstruction on Si(111) Surface
• Effect of the pH Value on the Rate of the Photoreduction of Methylene Blue by N-Phenylglycines

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