sn1 vs sn2

Question

Which substrate reacts fastest via SN1 in aqueous ethanol?

RankGuru · Accepted Answer

1. **SN1 Mechanism**: The rate-determining step is the formation of a carbocation intermediate.
2. **Rate Dependency**: The stability of the carbocation directly determines the reaction rate. Stability order: **Tertiary ($3^\circ$) > Secondary ($2^\circ$) > Primary ($1^\circ$) > Methyl**.
3. **Analysis of Substrates**:
   - $(CH_3)_3CCl$ (tert-butyl chloride): Forms a **tertiary carbocation**, $(CH_3)_3C^+$, stabilized by $9$ hyperconjugative $H$-atoms and $+I$ effect of three methyl groups.
   - $CH_3CH_2Cl$ and $CH_3CH_2CH_2Cl$: Form primary carbocations.
   - $CH_3Cl$: Forms a methyl carbocation (least stable).
4. **Conclusion**: **Tert-butyl chloride** reacts fastest due to its superior carbocation stability.

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sn1 vs sn2

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