チオクロム生成反応 : (II)ブロムシアンによるビタミンB_1よりチオクロムの生成とpHとの関係

概要

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Thiochrome was formed by adding cyanogen bromide into buffered thiamine solutions of different pH values between 6 and 12. Thiochrome was estimated by measuring its absorption maximum at 365mμ or the fluorescence of its butanolicextract. The formation of thiochrome was highest at pH 9〜11,and quicker at pH 10〜12 than at pH 7〜9. If the buffered thiamine solution was kept standing for one hour before adding cyanogen bromide to it, thiochrome was only obtained at pH less than 9.5,while cyanothiamine and thiamine disulde were formed at pH more than 10. Thiochrome was still attainable at neutral or slightly acidic medium even though the reaction was slow and imperfect. The solution of thiamine monohalide such as thiocyanate could be transformed into thiochrome by cyanogen bromide without NaOH to the extent of 30-40% yield on warming. This suggested that cyanogen bromide enabled to form thiochrome from pseudobase of thiamine and cyanothiamine from thiol form of thiamine.
日本ビタミン学会の論文