Question

The correct statement(s) about the following sugars $X$ and $Y$ is(are):

• A. $X$ is a reducing sugar and $Y$ is a non-reducing sugar
• B. $X$ is a non-reducing sugar and $Y$ is a reducing sugar
• C. The glucosidic linkages in $X$ and $Y$ are $\alpha$ and $\beta$, respectively
• D. The glucosidic linkages in $X$ and $Y$ are $\beta$ and $\alpha$, respectively

Answer 1

Answer: (B), (C)

The correct options are
B $X$ is a non-reducing sugar and $Y$ is a reducing sugar
C The glucosidic linkages in $X$ and $Y$ are $\alpha$ and $\beta$, respectively

In $X$, the glycosidic linkage is between two anomeric $C$ atoms, while in $Y$, it is only with one anomeric carbon, the other one is free. $X$ has the acetal linkage and $Y$ has the hemiacetal linkage. As we know that the carbohydrates with hemiacetal linkage are reducing in nature, and with acetal linkage are non-reducing in nature. Hence, it can be concluded from here that $X$ is a non-reducing sugar and $Y$ is a reducing sugar.

Also, $X$ is the $\alpha$ anomer, and $Y$ is the $\beta$ anomer of D(+) Glucose. Therefore, the glycosidic linkages in $X$ and $Y$ are $\alpha$ and $\beta$ respectively.