JEE Main 2026 · 4 Apr · Shift 2 · Chemistry Q68

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ChemistrySingle correct+4 / -1Question 68 of 75

A D-aldotetrose on oxidation with concentrated $\ce{HNO3}$ resulted in optically inactive dicarboxylic acid. The structure of the D-aldotetrose is:

Fischer projection CHO / HO-C-H / HO-C-H / CH₂OH (both OH on the left): L-erythrose.

Fischer projection CHO / H-C-OH / HO-C-H / CH₂OH (upper OH right, lower OH left): L-threose.

Fischer projection CHO / H-C-OH / H-C-OH / CH₂OH (both OH on the right): D-erythrose.

Fischer projection CHO / HO-C-H / H-C-OH / CH₂OH (upper OH left, lower OH right): D-threose.

Answer and worked solution

Official answer: C

Optically inactive acid. $\ce{HNO3}$ oxidises both ends to $\ce{COOH}$ . The tartaric acid formed is optically inactive (meso) only if the two OH groups are on the same side in the Fischer projection: erythrose.

D-sugar. The lowest OH is on the right, so it is D-erythrose, with both OH on the right.

(C)

Topics:Carbohydrates Optical isomerism and chirality

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JEE Main 2026 · 4 Apr · Shift 2, Chemistry question 68