Question

Assertion: benzonitrile is prepared by the reaction of chlorobenzene with $KCN$.
Reason: cyanide is a stronger nucleophile.
A. Assertion is true , reason is true; reason is the correct explanation for assertion.
B. Assertion is true, reason is true; reason is not the correct explanation for assertion.
C. Assertion is true , reason is false.
D. Assertion is false, reason is true.

Answer 1

so benzonitrile is the benzene ring basically to which the cyanide is added to it further it is also abbreviated as $PhCN$. Then we come to know that the formation of benzonitrile is not possible because the nucleophilic aromatic substitution reaction requires drastic changes.

Complete step by step answer:
Firstly we will discuss the benzonitrile so benzonitrile is the benzene ring basically to which the cyanide is added to it further it is also abbreviated as $PhCN$. Moreover we should know that it is the colourless liquid with a sweet bitter almond odour.
It is also given here that it is prepared by the reaction of the chlorobenzene with $KCN$ and after reaction the cyanide group replaces the chloro group in the chlorobenzene. Lets see whether it is possible or not.
Discussing more of the cyanide group we should know that it is called the cyano group also we should note here that there is a triple bond between the carbon and the nitrogen atom. Further it is present as an anion. Moreover the cyanide acts as a nucleophile because as we know that the nucleophiles are those which are having the strong negative charge. So the cyanide is found to contain the negative charge also as well as the lone pair of electrons.
Here we concluded that the aryl halides are heated with the alcoholic potassium cyanide solution we obtain the alkyl cyanides and further this is because of the cyanides higher nucleophilic behaviour. Moreover it is clear from this that the formation of benzonitrile is not possible because the nucleophilic aromatic substitution reaction requires drastic changes.

So, the correct answer is Option D.

Note: aryl halides do not undergo nucleophilic substitution reaction under ordinary conditions.also it should be known that the sodium and potassium salts of the cyanide are highly toxic.