Q17 / 90 · JEE Main 2019 (09 Apr Shift 2) · Chemistry

In the following reaction
carbonyl compound +MeOH⇌HClacetal

Rate of the reaction is the highest for:

  • A
    Acetone as substrate and methanol in stoichiometric amount
  • Correct answer
    B
    Propanal as substrate and methanol in excess
  • C
    Propanal as substrate and methanol in stoichiometric amount
  • D

    Acetone as substrate and methanol in excess

Solution

Acetal is form from the reaction of aldehyde with excess of MeOH
Figure

Formation of an acetal occurs when the hydroxyl group of a hemiacetal becomes protonated and is lost as water. The carbocation that is produced is then rapidly attacked by a molecule of alcohol. Loss of the proton from the attached alcohol gives the acetal.

Hence, the correct answer is option: 'B'.

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