From: Soren R. Jensen (oksrj$##$pop.dtu.dk)
Date: Fri Nov 03 2000 - 12:37:43 EST
Sharon,
You can of course follow this mutarotation by measuring the specific
rotation of the equlibrium mixture over 5-10 hours. - Soren
At 08:31 03-11-00 +0100, you wrote:
>Hi!
>Any other (besides NMR) way of observing the alpha/beta interconversion in
>water or in other media?
>-Sharon
>
>
>
>
>
>>Ashutosh,
>>It is true that the equilibrum mixture of alpha/beta-glucopyranose is ca.
>>40/60 in water; this can be seen by dissolving crystalline glucose in D2O
>>and immediately running the NMR spectrum to give a spectrum of the almost
>>pure alpha form. - However, after about 10 h the above eq. mix. is reached.
>>This is partly due to steric effects, partly to the "anomer effect" [cf.
>>J.March (3rd ed.) p. 128].
>>The former demands an quatorial position of the 1-OH group, the latter an
>>axial. However, in a very polar solvent like water, the "anomer effect" is
>>rather weak and the result is the above percentages in the mixture. - Soren
>>
>>At 23:08 01-11-00 +0530, you wrote:
>>>In an equilibrium solution of alpha and beta D-Glucopyranose there is a
>>slightly more percentage of the beta isomer.Is it due to some steric effect
>>or are some other factors involved too.
>>>Thanks
>>>Ashutosh S. Jogalekar
>>>Department of Chemistry
>>>University of Pune
>>>India
>><>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>
>>
>>Soren Rosendal Jensen tel: +45 45252103
>>Dept. of Organic Chemistry fax: +45 45 933968
>>Kemitorvet, Build. 201
>>Techn. University of Denmark
>>DK-2800 Lyngby, Denmark
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