JEE Advanced 2026 · Paper 2 · Chemistry Q4

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ChemistrySingle correct+3 / -1Question 40 of 54

A known artificial sweetener X is composed of 4-chloro-4-deoxy-α-D-galactose and 1,6-dichloro-1,6-dideoxy-β-D-fructose joined by a glycosidic linkage. Structure of D-galactose is given below:

The correct structure of X is

Fischer projection of D-galactose: CHO at top; OH on the right at C2, left at C3, left at C4, right at C5; CH₂OH at the bottom.

Chair pyranose with Cl axial (up) at C4 (galacto configuration) and the anomeric O axial (down, α), joined through O to C2 of a fructofuranose that carries CH₂Cl on C2 drawn up (β) and CH₂Cl on C5: sucralose.

As in (A) but with Cl equatorial at C4 of the pyranose (gluco configuration); same β-fructofuranoside part.

Pyranose with Cl equatorial at C4 (gluco configuration), joined to a fructofuranose whose C2 has the CH₂Cl drawn down and the glycosidic O up (α-anomer).

Pyranose with Cl axial at C4 (galacto configuration), joined to a fructofuranose whose C2 has the CH₂Cl drawn down and the glycosidic O up (α-anomer).

Answer and worked solution

Official answer: A

X is sucralose: 4-chloro-4-deoxy-α-D-galactopyranosyl 1,6-dichloro-1,6-dideoxy-β-D-fructofuranoside.

Pyranose half. D-galactose differs from D-glucose only at C4. In the $^4C_1$ chair the C4 substituent is therefore axial, so Cl must be axial at C4. The α-anomer has the glycosidic O axial (down) at C1.

(B) and (C) put Cl equatorial at C4: that is the gluco configuration. ✗

Fructose half. It must be the β-D-fructofuranoside, the same fructose unit as in sucrose, with C1 and C6 both as $\ce{CH2Cl}$ . (A) and (B) draw it this way: $\ce{CH2Cl}$ (C1) up at the anomeric C2, and the glycosidic O down.

Only (A) has both the galacto chlorine and the β-fructofuranoside.

Topics:Carbohydrates Optical isomerism and chirality

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JEE Advanced 2026 · Paper 2, Chemistry question 4