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Question:

Account for the following: (i) The C−Cl bond length in chlorobenzene is shorter than that in CH3−Cl. (ii) Chloroform is stored in closed dark brown bottles.

Solution:

  1. In chlorobenzene, the C−Cl bond is shorter due to partial double bond character between the carbon atom of the ring and the halogen atom.
  2. Chloroform is slowly oxidized by oxygen present in air in the presence of light to carbonyl chloride or phosgene. Phosgene is carbonyl chloride and is represented as COCl2. To prevent the formation of phosgene, chloroform is stored in dark colored bottles.