MCQ
Necessary conditions for halogenation are
  • A
    Cold and dark
  • B
    Presence of halogen carrier
  • Both $(a)$ and $(b)$
  • D
    None

Answer

Correct option: C.
Both $(a)$ and $(b)$
c
Necessary condition for halogenation is presence of halogen carrier.

Halogenation is done in dark without any catalyst then according to free radical mechanism new halide radical will be attached to benzylic carbon. This reaction is carried out in dark so that required energy is supplied in general if it would be carried out in light chlorine free radical would be formed but in dark we use heat and supply energy. For chlorination $1\, kcal$, bromination $16\, kcal$ and iodination $33\, kcal$.

in presence of catalyst like lewis acid like $AlCl _3$ and $FeCl _3$ electrophilic substitution takes place.

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