IIT-JEE 2010 · Paper 1 · Chemistry Q4

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ChemistrySingle correct+3 / -1Question 4 of 84

The correct statement about the following disaccharide is

A six-membered sugar ring (a) (a glucopyranose drawn in Haworth form, CH₂OH at C5, OH groups at C2, C3, C4) whose anomeric carbon carries a downward O-CH₂CH₂-O bridge; the bridge joins the anomeric carbon of a five-membered ring (b) (a fructofuranose in Haworth form with CH₂OH groups at C1 and C5).

Ring (a) is pyranose with

\alpha

-glycosidic link

Ring (a) is furanose with

\alpha

-glycosidic link

Ring (b) is furanose with

\alpha

-glycosidic link

Ring (b) is pyranose with

\beta

-glycosidic link

Answer and worked solution

Official answer: A

Ring (a) is six-membered (five carbons and the ring oxygen, $\ce{CH2OH}$ on C5): a pyranose. Its anomeric C-O bond to the bridge points down in the Haworth drawing, which (for a D-sugar with $\ce{CH2OH}$ up) is the α configuration.

Ring (b) is five-membered: a furanose, so (D) is wrong; and (B) misnames ring (a). (C) does not describe ring (b)'s link correctly (the drawn fructofuranose link is β, as in sucrose).

(A)

Topics:Carbohydrates

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IIT-JEE 2010 · Paper 1, Chemistry question 4