Question

Which of the following does not exhibit the phenomenon of mutarotation ?

• A. (-) fructose
• B. (+) sucrose
• C. (+) lactose
• D. (+) maltose

Answer 1

The correct option is B (+) sucrose

Reducing sugars that exist in hemiacetal and hemiketal forms, mutarotation in aqueous solution. During mutarotation, the ring open upto give the open-chain form which then recloses either in the inverted position or in the original position giving an equilibrium mixture of two anomers with a small amount of open-chain form.

Thus, all reducing monosaccharides and disaccharides undergo mutarotation in aqueous solution. Among the given carbohydrates, only sucrose is a non-reducing sugar as in it the hemiacetal and hemiketal groups of glucose and fructose are linked together through O-atom and thus, not free.

Due to the absence of a free hemiacetal or hemiketal group, sucrose does not exhibit mutarotation.

Hence, option B is correct.