What Is Happening When the Blue Bottle Bleaches: An Investigation of the Methylene Blue-Catalyzed Air Oxidation of Glucose

An investigation of the Blue Bottle Experiment, a well-known lecture demonstration reaction involving the dye-catalyzed air oxidation of a reducing sugar in alkaline solution, has delineated the sequence of reactions leading to the bleaching of the dye, the regeneration of color, and so forth. Enoli...

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Bibliographic Details
Published in:Journal of chemical education 2012-10, Vol.89 (11), p.1425-1431
Main Authors: Anderson, Laurens, Wittkopp, Stacy M, Painter, Christopher J, Liegel, Jessica J, Schreiner, Rodney, Bell, Jerry A, Shakhashiri, Bassam Z
Format: Article
Language:English
Subjects:
Acids
Bleaches
Bleaching
Catalytic oxidation
Chemical reactions
Chemistry
College Science
Color
Dyes
Glucose
Graduate Study
Methylene blue
Molecular Structure
NMR
Nuclear magnetic resonance
Oxidation
Regeneration
Science Experiments
Science Instruction
Scientific Concepts
Spectrum analysis
Sugar
Undergraduate Study
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Summary:An investigation of the Blue Bottle Experiment, a well-known lecture demonstration reaction involving the dye-catalyzed air oxidation of a reducing sugar in alkaline solution, has delineated the sequence of reactions leading to the bleaching of the dye, the regeneration of color, and so forth. Enolization of the sugar is proposed as a key step in the sequence. The first-order rate constant for this step was found to be ∼2.3 × 10–3 min–1 with respect to total sugar concentration under the conditions used (0.184 M glucose, pH 13.3, 25 °C). Measurements with an oxygen-sensing electrode on Blue-Bottle mixtures containing varying quantities of methylene blue indicated that in a usual demonstration the rate of O2 consumption is ∼60% of the enolization rate. Small samples of the organic oxidation product were isolated and found by chromatographic and NMR-spectroscopic examination to consist primarily of the 5-carbon sugar acid arabinonic acid.
ISSN:0021-9584
1938-1328
DOI:10.1021/ed200511d