In an SN2 reaction the configuration at the reacting carbon atom is
Correct answer: A. inverted, because the nucleophile attacks from the side opposite the leaving group
- A. inverted, because the nucleophile attacks from the side opposite the leaving group
- B. retained completely
- C. randomised, giving a racemic mixture
- D. unchanged because no bond is broken
Explanation
Back side attack turns the three remaining groups inside out like an umbrella in the wind, so an optically active substrate gives a product of opposite configuration, an effect called Walden inversion. An SN1 reaction gives a racemic mixture instead, because the planar carbocation can be attacked equally from either face. Stereochemistry is therefore the clearest experimental way to distinguish the two mechanisms.
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About Nucleophilic Substitution
Nucleophilic substitution replaces a leaving group in an alkyl halide when an electron-rich nucleophile attacks the carbon atom. The topic compares SN1 and SN2 mechanisms, including reaction conditions, substrate structure, solvent effects, nucleophile strength, carbocation formation and stereochemical changes, and distinguishes substitution from elimination.
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