Dolbier HW Solutions 627

Dolbier HW Solutions 627 - 721 CARBOHYDRATES (c) The...

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( c ) The pyranose form of D -xylose is just like that of D -glucose except that it lacks a CH 2 OH group. We would expect the equilibrium between pyranose forms in D -xylose to be much like that in D -glucose and predict that the b -pyranose form would predominate. It is observed that the b y a ratio in D -xylose is 64 : 36, exactly the same as in D -glucose. ( d ) The pyranose form of D -lyxose is like that of D -mannose except that it lacks a CH 2 OH group. As in D -mannopyranose, the a form should predominate over the b . The observed a y b distribution ratio in D -lyxopyranose is 73 : 27. 25.30 ( a ) The rate-determining step in glycoside hydrolysis is carbocation formation at the anomeric position. The carbocation formed from methyl a - D -fructofuranoside (compound A) is tertiary
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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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