Chemistry 332 - Spring 1996
Elements of Organic Chemistry II
Quiz, Chapter 14 - Carbohydrates
1. (4 points) Write a Haworth diagram and a chair structure for alpha-D-galactopyranose.
Galactose differs from glucose only at C-4.
2. (4 points) D-Fructose is a ketohexose that assumes mainly a furanose
structure in solution (shown below). Number the carbons in the ring, deduce
what the open-chain form of D-fructose must look like (in the standard Fischer
projections), and compare its structure with that of D-glucose.
D-fructose is identical to D-glucose at carbons 3,4,5, and 6, and they
differ at carbons 1 and 2 (fructose is a ketose and glucose is an aldose).
3. (2 points) Decide whether or not D-galactose and D-fructose are reducing
sugars.
D-galactose - YES (it is an aldose)
D-fructose - NO (it is a ketose)