How come sucrose is a non-reducing sugar?

[vDDmaniaC]

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A while back, I asked the difference between ketal hemital acetal hemi-acetal, at that time I realized that reducing sugar has OH sub at carbon #1. If not it is a non-reducing sugar. So I went through Top score, and the number 86. It says sucrose is nonreducing sugar. Evey carbon I am looking on this molecule has OH subs. How come it is a non-reducing sugar?

 

[topdent1]

you need to look at the anomeric carbon. The anomeric carbon does not link with hydroxide.

 

[vDDmaniaC]

Then whenever I see the anomeric carbon then it has to be a non-reducing sugar?

 

[topdent1]

Then whenever I see the anomeric carbon then it has to be a non-reducing sugar?

I don't understand what you said..but it works like this. If the anomeric carbon( the one attached to two oxygens) has one of the oxygens in the form of a hydroxide attached to it, than it is reducing. If their are no hydroxides, it is non reducing.

 

[orthodocs12]

a reducing sugar, as topdent said, has an OH on the C-1, the anomeric carbon. the reason it is reducing is recognized by the hemiacetal the OH makes with the O of the ring. if theres no OH on the the C-1 carbon, then no hemiacetal is present, this making it a non-reducing sugar.