Studies of Aliphatic Hydroxycarboxylic Acids as Antioxidant. V. Complexes of Copper(II) with <I>erythro</I>- and <I>threo</I>-2-Methyltartaric, and <I>meso</I>- and <I>threo</I>-2,3-Dimethyltartaric Acids

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概要

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• The dissociation constants of <I>erythro</I>- and <I>threo</I>-2-methyltartaric and <I>meso</I>- and <I>threo</I>-2,3-dimethyltartaric acids were determined by the potentiometric titration method at the ionic strength of μ=0.1 and at 22°C. The values of the dissociation constants were p<I>K</I><SUB>1</SUB>=3.54 and p<I>K</I><SUB>2</SUB>=5.03 for <I>erythro</I>-2-methyltartaric acid, and p<I>K</I><SUB>1</SUB>=3.28 and p<I>K</I><SUB>2</SUB>=4.70 for the <I>threo</I>-form. For <I>meso</I>-2,3-dimethyltartaric acid, the corresponding values were 3.52 and 4.98, while the <I>threo</I>-form had values of 3.04 and 5.30. The complex formation of copper(II) with these acids has been investigated using Job's method of continuous variations at the ionic strength of μ=0.2 and at 22°C. Copper-(II) and <I>erythro</I>-2-methyltartaric acid react in a 1 : 1 ratio at pH 2.40 and in a 3 : 2 ratio at pH 5.00. On the other hand, the <I>threo</I>-form does not combine with copper(II) at pH 2.40, though it does react at pH 5.00 in a 1 : 1 ratio. As for <I>meso</I>-2,3-dimethyltartaric acid, the complex formation in a 3 : 2 ratio was observed at pH 5.00. However, the <I>threo</I>-form and copper(II) react in a 1 : 2 ratio at pH 5.00. The equilibrium constants (apparent stability constants) were calculated by the method of Turner and Anderson. The values of the equilibrium constant were log <I>K</I>=9.71 (pH 5.00) and log <I>K</I>=2.02 (pH 2.40) for <I>erythro</I>-2-methyltartaric acid, log <I>K</I>=3.78 (pH 5.00) for the <I>threo</I>-form, log <I>K</I>=9.70 (pH 5.00) for <I>meso</I>-2,3-dimethyltartaric acid, and log <I>K</I>=5.19 (pH 5.00) for the <I>threo</I>- form. On the basis of these data, the structures of these complexes are discussed.

• 公益社団法人 日本化学会の論文

著者

• Masuyama Shinroku

  The Osaka Municipal Technical Research Institute

• Horikawa Kazuo

  The Osaka Municipal Technical Research Institute

関連論文

• Studies of Aliphatic Hydroxycarboxylic Acids as Antioxidant. V. Complexes of Copper(II) with erythro- and threo-2-Methyltartaric, and meso- and threo-2,3-Dimethyltartaric Acids
• Studies of Aliphatic Hydroxycarboxylic Acids as Antioxidants. III. The Preparation of Two Isomers of Hydroxycitric Acid Lactone (erythro- and threo-3,4-dicarboxy-3-hydroxy-γ-butyrolactone)

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