Chiral centres in glucose and fructose
Does beta-D-fructose in its cyclic form have the same number of chiral carbons as beta-D-glucose? Show the structural formulas and chiral carbons.
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I have attached the structures of glucose and fructose in MS word format.
Basically, you just need go through all of the carbon centres and see whether they are chiral. In other words, you need to check whether any of the constituents on the carbon atom are the same. So for carbon 1 of beta-D-glucose, the contituents are a hydrogen atom (not shown, but pointing into the page), a hydroxyl group, an oxygen atom, and a carbon atom. So since none of these are the same, carbon 1 is chiral. Another way of thinking of this is if you interchanged two of the constituents, you would change the configuration of the molecule (from R to S or from S to R).
Carbon 6 of beta-D-glucose is not chiral because it has two hydrogen atoms attached. Same goes for carbons 1 and 6 of beta-D-fructose. So if you interchanged two of the groups on such a carbon, you do not change the stereochemistry.
So if you go through all the other carbon centres you should find that they are chiral.
To summarize,
beta-D-glucose: 1,2,3,4, and 5 are chiral; 6 is not.
beta-D-fructose: 2,3,4,5 are chiral; 1 and 6 are not.