I think that you should look at the anomeric carbon. And this carbon should be able to give off a free proton. I think that hemiacetals can be reducing sugar because they have the extra H that can be taken off. And I doubt that hemiketals sugar have the extra H in the anomeric carbon to give off.
The central carbon on the hemiketal can be oxidized as the C-O-H group can be changed to a carbonyl group (C=O). Since the hemiketal can be oxidized, it is a reducing agent (or more specifically a reducing sugar if that is what the molecule is).
The central carbon on the ketal can't be oxidized so it can't act as a reducing agent.
The same idea can be applied to looking at the anomeric carbon on a sugar to see if it can be oxidized. If it can, then the sugar is a reducing sugar. Hope that helps!
This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies and terms of service.