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🧪 Chemistry  ·  Haloalkanes & Haloarenes  ·  NEET & JEE

The SN2 reaction has a second-order rate law. If the concentration of both the substrate (RX) and the nucleophile (Nu) are each doubled, the rate:

Answer: Quadruples.

  • A Doubles
  • B Quadruples
  • C Remains the same
  • D Increases 8-fold

Correct answer: B. Quadruples

Explanation: Rate = k[RX][Nu]. Doubling both concentrations: Rate = k(2[RX])(2[Nu]) = 4k[RX][Nu]. The rate increases 4 times (quadruples).

SN2: one stepNu-CX-backside attackNuC+ X-Inversion of configuration(Walden inversion)SN1: two stepsCX-slow: leaving group exits+CcarbocationNu-Planar intermediate givesracemisation (both faces attacked)

SN2 proceeds in a single step with backside attack and inversion of configuration, while SN1 forms a planar carbocation intermediate first, leading to racemisation.

Concept context

Study carbon-halogen compounds: how they are made, how they react via SN1/SN2 and elimination, their stereochemistry, and their environmental impact.

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