Dolbier HW Solutions 626

Dolbier HW - 720 CARBOHYDRATES(b HO HO Laetrile undergoes an analogous hydrolytic cleavage to yield the cyanohydrin of benzaldehyde CO2H O OCHC6H5

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( b ) Laetrile undergoes an analogous hydrolytic cleavage to yield the cyanohydrin of benzalde- hyde. 25.29 Comparing D -glucose, D -mannose, and D -galactose, it can be said that the con f guration of C-2 has a substantial effect on the relative energies of the a - and b -pyranose forms, but that the con f gura- tion of C-4 has virtually no effect. With this observation in mind, write the structures of the pyranose forms of the carbohydrates given in each part. ( a ) The b -pyranose form of D -gulose is the same as that of D -galactose except for the con f gura- tion at C-3. The axial hydroxyl group at C-3 destabilizes the a -pyranose form more than the b form be- cause of its repulsive interaction with the axially disposed anomeric hydroxyl group. There should be an even higher b y a ratio in D -gulopyranose than in D -galactopyranose. This is so; the observed b y a ratio is 88 : 12. ( b ) The b -pyranose form of D -talose is the same as that of D -mannose except for the con f guration
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This note was uploaded on 10/03/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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