Chemistry Hydrocarbons MDCAT 2017
PMDC Verified Question 48 of 65
Chlorination and Bromination mostly uses:
A
Radiowaves
B
Infrared radiation
C
Visible light
D
U.V light
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: U.V light
Concept:

Free radical halogenation of alkanes (chlorination and bromination) requires high-energy initiation to homolytically cleave the covalent halogen-halogen bond.

Solution:

  • The Cl-Cl and Br-Br bonds require a specific quantum of energy to undergo homolytic fission (breaking equally to form two free radicals).


  • Ultraviolet (U.V.) light provides the exact frequency and sufficient energy required for this photochemical initiation step.


Why other options are incorrect:

  • Radiowaves and Infrared radiation are too low in energy to break covalent bonds (they cause nuclear spin transitions and molecular vibrations, respectively).


  • Visible light does not possess sufficient energy to reliably initiate typical chlorination without specialized setups.

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