D.C. polarographic reduction wave of 2,3-diketo-L-gulonic acid of carbonyl groups in aqueous solution.

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Other Title
  • 2,3‐ジケト‐L‐グロン酸のカルボニル基に起因する直流ポーラログラフ還元波
  • 2 3 ジケト L グロンサン ノ カルボニルキ ニ キインスル チョクリュウ
  • 2,3-ジケト-L-グロン酸のカルボニル基に起因する直流ポーラログラフ還元波

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Abstract

Polarographic reduction wave and hydration of carbonyl groups of 2, 3-diketo-L-gulonic acid (DKG) were studied in various pH solutions by d.c. polarography, cyclic voltammetry and spectrophotometry. Three kinds of polarographic reduction waves A [half wave potential (E1/2) = -0.67 V vs. SCE], A and B (E1/2= -1.11 V) and B and C (E1/2= -1.02 V) obtained in acid, neutral and alkaline solutions, respectively, were observed due to the carbonyl groups of DKG. Same kind of reduction waves were also observed in various pH solutions using cyclic voltammogram, but no corresponding oxidation waves were seen, indicating the reaction to be irreversible. Formation of 3, 4- and 2, 3-endiol forms of 2, 3-diketo-L-gulono-δ-lactone (3, 4- or 2, 3-End.DKGL, respectively) from DKG via isomerization and cyclization was tested spectrophotometrically. In neutral solution, only 3, 4-End.DKGL was observed, while both the 3, 4- and 2, 3-forms were observed in alkaline solution (pH 10.8). Based on these results, the carbonyl groups of DKG are found to have at least three different hydration forms which could be fully hydrated in acidic pH range, mono-hydrated at the C-3 position in neutral pH range, and not hydrated in alkaline pH range. The pathway for the formation of 3, 4- and 2, 3- End.DKGL from DKG was proposed.

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 42 (3), 159-165, 1993

    The Japan Society for Analytical Chemistry

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