Question

Which of the following statements are true?
(1) Maltose forms an osazone
(2) Lactose undergoes mutarotation.
(3) Galactose is a $C _{4}$-epimer of glucose
(4) In starch, the glucose units are linked by " $\beta$-linkages

• A. 1, 2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (A)

Maltose, $\left( C _{12} H _{22} O _{11}\right)$, a disaccharide, reacts with phenyl hydrazine to give an osazone $C _{12} H _{20} O _{9} \left(= N \cdot NHC _{6} H _{5}\right)_{2}$.
All monosaccharide and reducing disaccharide undergo mutarotation.
The structure of glucose and galactose are as

Thus, galactose is $C-4$ epimer of glucose.
In starch, the glucose units are linked by $\alpha$-linkages.