Chapter 25: Carbohydrates
Aldoses and Ketoses
Carbohydrates are really just polyhydroxyaldehydes, the
, or polyhydroxyketones, the
So, for a carbohydrate to be an
it needs an
Remember that an aldehyde group, here shown as CH=O, is also often written as CHO.
And to be a
it needs a
The critical centers are marked in the diagrams with
The assignment is quite apparent in the acyclic form of the sugar, see above.
In the cyclic form, find the anomeric center (
) and then look at the substituents there. If one is an H, then it is an aldose (see glucose example above).
The systems are further classified depending on
how many C atoms
there are (see above for examples)
4 C =
5 C =
6 C =
Dr. Ian Hunt
, Department of Chemistry, University of Calgary