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)

JEE Main 201912 AprilEvening Shift

JEE Main 2019 · 12 April · Evening Shift · Chemistry · Haloalkanes and Haloarenes

An ‘Assertion’ and a ‘Reason’ is given...

An ‘Assertion’ and a ‘Reason’ is given below. Choose the correct answer from the following options:
Assertion

\left(A\right)

: Vinyl halides do not undergo nucleophilic substitution easily.
Reason \left(R\right)

: Even though the intermediate carbocation is stabilized by loosely held

\pi -$ electrons, the cleavage is difficult because of the strong bonding.

ABoth $\left(A\right)$ and \left(R\right) $are correct statements but \left(R\right)$ is not the correct explanation of \left(A\right) .
BBoth $( A )$ and $( R )$ are wrong statements.
CBoth $\left(A\right)$ and \left(R\right) $are wrong statements and$ ( R ) $is the correct explanation of \left(A\right) .$
D $\left(A\right)$ is a correct statement but $\left(R\right)$ is a wrong statement.

D. $\left(A\right)$ is a correct statement but $\left(R\right)$ is a wrong statement.

{\text{CH}_{2} = CH - Cl

does not undergo unimolecular nucleophilic substitution

( S{N}^{1} )

reaction due to the formation of highly unstable cation

\left(C{H}_{2} = \overset{⊕}{CH}\right),

which can not be delocalized by

\pi -

electrons. It does not give

S{N}_{2}

because

\pi{e}^{-}

cloud is exposed, so, hindrance is there.