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In the Laboratory
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Use of Optical Rotation and NMR Signal Counting To Identify Common Aldoses
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John Almy
Chemistry Department, California State University, Stanislaus, Turlock, CA 95382
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May 2004
Vol. 81 No. 5
p. 708
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| Abstract |
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An inexpensive, small scale experiment for second semester organic students describes the unambiguous identification of a common aldose "unknown" from five possible candidates: glucose, mannose, galactose, arabinose, or xylose. The aldose is first reduced to an alditol to permit possible symmetry in the molecule. The alditol is then converted to its peracetate for improved crystallization and analysis by polarimetry and NMR. Without referring to melting points in the literature or published spectra, students examine the symmetry properties of each candidate's alditol peracetate to determine which structure fits the rotational data and NMR spectra. As an option, the ketoses, sorbose and fructose, can be similarly reduced and acetylated. Each will produce peracetate mixtures that can be identified by NMR using the information obtained from the aldoses, again without the need for published data.
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| Supplement |
A set of instructions for students, relevant spectra, and extensive notes for the instructor are available.
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 Contents |
Folder JCE2004p0708W containing JCE2004p0708.doc (Microsoft Word), fig1.pdf, fig2.pdf, fig3.pdf, and fig4.pdf<
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| More Information |
Citation |
Almy, John. J. Chem. Educ. 2004 81 708.
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Keywords |
Carbohydrates; Laboratory Instruction; Microscale; Molecular Properties / Structure; NMR Spectrometry; Organic Chemistry; Stereochemistry
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History |
Created:
Last Updated: |
April 1, 2004
February 18, 2005
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| Home > JCE Print > Journal of Chemical Education > Issues >
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