In an SN2 reaction (e.g., CH₃Br + OH⁻):
AThe reaction is zero order
BThe reaction occurs without a transition state
CThe reaction is second order (first order each in alkyl halide and nucleophile); proceeds via a single concerted step with inversion of configuration
DThe reaction is first order overall and proceeds via a stable carbocation intermediate
Answer & Solution
Correct answer: C. The reaction is second order (first order each in alkyl halide and nucleophile); proceeds via a single concerted step with inversion of configuration
**SN2 = bimolecular nucleophilic substitution**. **Rate ∝ [R-X][Nu⁻]** (second order overall). Single concerted step with a transition state where Nu and X are partially bonded → **inversion of configuration** (Walden inversion, 'umbrella inversion').
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