The Role of Anion in the Demethylation Reaction of Methylcobalamin with Mercuric Salts

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概要

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• The demethylation of methylcobalamin with mercuric salts containing ClO<SUB>4</SUB><SUP>−</SUP>, AcO<SUP>−</SUP>, Cl<SUP>−</SUP>, Br<SUP>−</SUP>, SCN<SUP>−</SUP>, or CN<SUP>−</SUP> was kinetically investigated by a conventional spectroscopic technique. The rates of reaction for mercuric chloride were proportional to [CH<SUB>3</SUB>–Co] and [HgCl<SUB>2</SUB>] while those for acetate depended little on [Hg(AcO)<SUB>2</SUB>], but increased in proportion with [AcO<SUP>−</SUP>]. The rates of reaction varied depending on the concentration and species - of anion, and the following sequence was obtained: AcO<SUP>−</SUP>>>Cl<SUP>−</SUP>≥SCN<SUP>−</SUP>≥Br<SUP>−</SUP>>>CN<SUP>−</SUP>. The sequence was reversely correlated with the stability constant of the equilibrium reaction, HgL<SUB><I>n</I>−1</SUB>+L\rightleftarrowsHgL<I><SUB>n</SUB></I>(<I>n</I>=1 or 2), so that it was considered that HgL<SUP>+</SUP> is an attacking electrophile in the cleavage of cobalt-carbon bond by the mercuric salts. The activity of HgCl<SUB>4</SUB><SUP>2−</SUP> for the reaction was somewhat lower than that of HgCl<SUB>2</SUB> while that of HgClCN was lower to a greater extent.

• 公益社団法人 日本化学会の論文

著者

• Yamamoto Haruhiko

  Faculty Of Agriculture Yamaguchi University

• Kwan Takao

  Faculty Of Pharmaceutical Sciences Teikyo University

• Chen Ju-Ling

  Faculty of Pharmaceutical Sciences, University of Tokyo

• Yokoyama Takashi

  Faculty of Pharmaceutical Sciences, University of Tokyo

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