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JEE Main201912 Apr 2019Evening ShiftChemistryHaloalkanes and HaloarenesActual

An ‘Assertion’ and a ‘Reason’ is given below. Choose the correct answer from the following options: Assertion A : Vinyl halides do not undergo nucleophilic substitution easily. Reason R : Even though the intermediate carbocation is stabilized by loosely held π - electrons, the cleavage is difficult because of the strong bonding.

Options

  1. ABoth A and R are correct statements but R is not the correct explanation of A .
  2. BBoth ( A ) and ( R ) are wrong statements.
  3. CBoth A and R are wrong statements and ( R ) is the correct explanation of A .
  4. DA is a correct statement but R is a wrong statement.

Correct answer

D. A is a correct statement but R is a wrong statement.

Step-by-step solution

CH 2 = C H - C l does not undergo unimolecular nucleophilic substitution ( S N 1 ) reaction due to the formation of highly unstable cation C H 2 = C H ⊕ , which can not be delocalized by π - electrons. It does not give S N 2 because π   e - cloud is exposed, so, hindrance is there.

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