question_answer 1)

  Arrange the following alkyl halides in decreasing order of the rate of \[\beta \]-elimination reaction with alcoholic KOH. (A) \[{{H}_{3}}C-C\equiv {{C}^{-}}\]         (B) \[H-C\equiv {{C}^{-}}\]                           (C) \[{{H}_{3}}C-CH_{2}^{-}\] (a) \[A>B>C\]                    (b) \[C>B>A\]                    (c) \[B>C>A~~~~~~~~~~\]          (d) \[A>C>B\]

Answer:

  (d) More the number of\[\beta \]-substituents more stable alkene and it will give on \[\beta \]-elimination. Since (A) has two \[C{{H}_{3}}\] and (C) has one \[\beta \]-methyl substituent while (B) has no \[C{{H}_{3}}\]substituent, therefore, reactivity towards p-elimination decreases in the order: A > C > B.