Which among the following is NOT a feature of $\mathrm{S}_{\mathrm{N}} 1$ mechanisms?

Which among the following is NOT a feature of $\mathrm{S}_{\mathrm{N}} 1$ mechanisms?
  1. Involve only backside attack of nucleophile.
  2. In an optically active substrate the product formed is racemic.
  3. Two step mechanism.
  4. Heterolysis of $\mathrm{C}-\mathrm{X}$ bond forms carbocation intermediate.

Solution

(1) When $\mathrm{C}$ is chiral, then product of $\mathrm{SN}^1$ reaction is racemic mixture, \& the reaction is known as racemization. In planner carbocation nucleophile attack from both front and back side. In $\mathrm{SN}^1$ reaction both inversion \& retention of configuration takes place. (2) Two step mechanism Thus, option A is incorrect (3) Heterolysis of C $-\mathrm{X}$ bond forms carbocation intermediate

Asked in: MHT CET 2021 (24 Sep Shift 2)

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