question_answer

  (i) Why are haloalkanes more reactive towards nucleophilic substitution reactions than haloarenes? (ii) Which one of the following two substances undergoes Syl reaction faster and why?  Or Write the structures and names of the compounds formed when compound A with molecular formula  is treated with the presence of .                                                                                                                              [2]

Answer:

  In haloarenes (C?Cl) bond is stabilised by resonance. It acquires certain double bond character. Also it is attached to -hybridised carbon. In haloalkanes, resonance stabilisation" of (C?Cl) bond does not take place. Also Cl is attached to -hybridised carbon which is less electronegative than -hybridised carbon in haloarenes. Thus, haloalkanes are more reactive for  reactions than haloarenes. (ii)   [1] In (A),carbocation formed is more stable than carbocation from (B).                         [1] Or