JEE Main · 2026 · 24 Jan 2026 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

A hydroxy compound (X) with molar mass 122 g

mol^{- 1}

is acetylated with acetic anhydride, using a large excess of the reagent ensuring complete acetylation of all hydroxyl groups. The product obtained has a molar mass of

290 g mol^{- 1}

. The number of hydroxyl groups present in compound

(X)

is :

(A)3
(B)5
(C)2
(D)4✓ Correct

Answer: (D)

Solution

Acetylation converts each

- OH

(mass

17

) into

- OCOC H_{3}

(mass

59

), a gain of

42 g mo l^{- 1}

for every hydroxyl group. The total mass gained is

290 - 122 = 168 g mo l^{- 1}

. The number of hydroxyl groups is

168/42 = 4

JEE Main · 2026 · 24 Jan 2026 · Shift 1 · Single correct option

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