Q36 / 155 · WBJEE 2024 · Chemistry

Which of the following statements about the $\mathrm{S}_{\mathrm{N}} 2$ reaction mechanism is/are true?

  • Correct answer
    A
    The rate of reaction increases with increasing nucleophilicity.
  • B
    The number 2 denotes a second order reaction
  • Correct answer
    C
    Tertiary butyl substrates do not follow this mechanism
  • D
    The optical rotation of substrates always changes from (+) to ( - ) or from ( - ) to (+) in the products

Solution

Hint: $S_N 2$ reaction rate depends upon the nucleophilicity of the attacking nueleophile. Here the 2 in the notation stands for Bimolecularity. Tert-butyl substrate fails in $\mathrm{S}_{\mathrm{N}} 2$ due to crowding. Optical rotation does not change necessarily from $(+)$ to $(-)$ or $(-)$ to $(+)$, as the product is not necessarily an isomer of reactant.

Hence, the correct answer is options: 'A', 'C'.

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