sn2 sterics

Question

SN2 rate decreases in order:

RankGuru · Accepted Answer

1. **SN2 Mechanism**: This is a single-step concerted process where the nucleophile attacks from the side opposite to the leaving group.
2. **Transition State**: A pentacoordinate transition state is formed. Since the nucleophile must approach the central carbon, **steric hindrance** is the dominant factor.
3. **Steric Order**: Methyl halides ($CH_3X$) have the least hindrance, while tertiary halides ($(CH_3)_3CX$) are extremely crowded.
4. **Reactivity Order**: **Methyl > Primary > Secondary >> Tertiary**.
5. **Applying to Options**: **$CH_3Cl > CH_3CH_2Cl > (CH_3)_2CHCl > (CH_3)_3CCl$**.

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sn2 sterics

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