IIT-JEE 2009 · Paper 2 · Chemistry Q9

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ChemistryMultiple correct+4 / -1Question 9 of 57

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

X (Haworth): sucrose, α-D-glucopyranose C1 joined through O to C2 of β-D-fructofuranose (both anomeric carbons used in the link).

Y (Haworth): a β-D-glucopyranose unit whose C1 is joined through O (β, pointing up) to C4 of a second pyranose ring that keeps a free anomeric OH at C1. As printed, the second ring has its C2-OH up and C3-OH down.

X is a reducing sugar and Y is a non-reducing sugar

X is a non-reducing sugar and Y is a reducing sugar

The glucosidic linkages in X and Y are

\alpha

and

\beta

, respectively

The glucosidic linkages in X and Y are

\beta

and

\alpha

, respectively

Answer and worked solution

Official answer: B, C

X is sucrose: C1 of α-D-glucose is linked to C2 of β-D-fructose, so both anomeric carbons are used and the sugar is non-reducing. The glucosidic link is α.

Y has a β-glucose whose C1 is linked to C4 of the second ring, which keeps a free anomeric OH at C1: a reducing sugar with a β link.

(B), (C)

Topics:Carbohydrates

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IIT-JEE 2009 · Paper 2, Chemistry question 9