A mechanism is drawn in which a hydroxide ion approaches the carbon of chloromethane from the side opposite the chlorine atom. In the transition state the carbon is joined to five groups, with OH and Cl partly bonded on a straight line through it and the three hydrogens in one plane. Then chlorine leaves and the three hydrogens turn inside out like an umbrella in the wind. Which statement about this reaction is correct?
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Backside attack, a single transition state holding both nucleophile and leaving group, and the umbrella flip describe the SN2 mechanism. Its rate depends on both reactants, rate = k[CH3Cl][OH⁻], and a chiral carbon undergoes inversion of configuration.
- B.
SN1 proceeds through a carbocation; this single-step backside attack with a five-coordinate transition state is SN2.
- C.
Both the substrate and the nucleophile are in the transition state, so the rate depends on both, and backside attack inverts the configuration.
- D.
SN1 is first order, depending only on the substrate; a rate depending on both reactants is SN2.
NCERT: Class 12 Chemistry, Chapter 6