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JEE Advanced levelSingle correct optionDifficulty 3 of 3bm247

The compound shown is first treated with Tollens' reagent (step 1) and, separately, a sample is warmed with dilute aqueous acid, neutralised, and then treated with Tollens' reagent (step 2). Which outcome is correct?

  1. AStep 1 positive, step 2 positive
  2. BStep 1 negative, step 2 negative
  3. CStep 1 positive, step 2 negative
  4. DStep 1 negative, step 2 positive

Answer: D

The anomeric carbon carries OCH3, so the compound (methyl alpha-D-glucopyranoside) has no free hemiacetal and gives no silver mirror in step 1. Dilute acid hydrolyses the acetal to D-glucose and methanol. The liberated D-glucose has a free hemiacetal and reduces Tollens' reagent in step 2.
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