|Problem Set #15||March 27, 1998|
1. A) Draw the Fischer projections for the four aldotetroses
B) Show which are the D-monosaccharides
C) Which are enantiomers?
2 Mannose in aqueous solution exists as a mixture of -D-mannopyranose and -D-mannopyranose.
Draw Haworth projections of each of these molecules.
3. D-Fructose when dissolved in water exists as an equilibrium mixture of -D-fructopyranose (3%), -D-fructopyranose (57%), -D-fructofuranose (9%), -D-fructofuranose (31%), and D-fructose (0.01%).
A) Draw a Fischer projection of D-fructose.
B) Draw chair type structures for the two pyranoses, clearly showing the stereochemistry.
C) Draw stereodiagrams of the two furanoses, again clearly showing their stereochemistry.
D) Write a mechanism for the interconversion of -D-fructopyranose and -D-fructofuranose in water. Assume the reaction is acid catalysed.
4. Also tackle some of the problems on amines given in Ege Chapter 22.
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27 mar 98; jp