Q18 / 100 · BITSAT 2024 (Memory Based Paper 1) · Chemistry

An unknown alochol is treated with the "Lucas reagent" to determine whether the alcohol is primary, secondary or tertiary. Which alcohol reacts fastest and by what mechanism :

  • A
    secondary alcohol by $\mathrm{S}_{\mathrm{N}} 1$
  • Correct answer
    B
    tertiary alcohol by $\mathrm{S}_{\mathrm{N}} 1$
  • C
    secondary alcohol by $\mathrm{S}_{\mathrm{N}} 2$
  • D
    tertiary alcohol by $\mathrm{S}_{\mathrm{N}} 2$

Solution

The reaction of alcohol with Lucas reagent is mostly an $\mathrm{S}_{N}1$ mechanism reaction and the rate of reaction is directly proportional to the carbocation stability formed in the reaction, hence tertiary alcohol will react fastest.

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

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