Question

Aniline, chloroform and alc. KOH on heating gives:
A.phenyl isocyanide
B. phenyl cyanide
C. chloro benzene
D.phenol

Answer 1

Hint: When the reactants are taken then after reaction the product which is formed, has a very foul smell. It is used to check the presence of primary amines, other amines do not give a foul smell.

Complete step by step solution:
In order to answer our question, let us get to know about amines. As an 'N' atom in NH, the molecule is $s{{p}^{3}}$ hybridised and tetrahedral in geometry. Similarly 'N' atom in all amines is also $s{{p}^{3}}$ hybridised which has tetrahedral geometry but their shape is pyramidal. Out of four hybrid orbitals of nitrogen three orbitals overlap with hydrogen or carbon atoms of the alkyl group depending upon the composition of amines, whereas the fourth hybrid orbital contains a lone pair of electrons. Repulsion between lone pair and bond pair of electrons suppresses the bond angle which becomes lesser than ${{109.5}^{0}}$ Arylamines have $N{{H}_{2}}$ group directly attached to the benzene ring. They are named as derivatives of aniline or benzenamine. aqueous state. Aromatic amines such as aniline are less basic than ammonia because aromatic amines are far less basic than ammonia and aliphatic amines. It is because, in aniline or other arylamines, the $N{{H}_{2}}$ As we know, greater the number of resonating structures, greater is the stability. Thus we can conclude that aniline is more stable than anilinium ion. Hence, the ability to accept ${{H}^{+}}$ would be less in aniline than if the group is attached directly to the benzene ring. The unshared electron pair on nitrogen atoms is in conjugation with the benzene ring and thus making it less available for protonation.
Now, let us come to our question. Aliphatic and aromatic primary amines when heated with chloroform and ethanolic potassium hydroxide form isocyanides or carbylamines which are foul smelling substances. So, we have:
\[R-N{{H}_{2}}+CHC{{l}_{3}}+3KOH(alc)\xrightarrow{\Delta }{{C}_{6}}{{H}_{5}}NC+3KCl+3{{H}_{2}}O\]

The product formed in the reaction is phenyl isocyanide. So we get the correct answer as option A.

NOTE: It is to be noted that this reaction is also called Carbylamine reaction. It gives a foul smell when the isocyanide is formed. Moreover, it does not react with ${{2}^{0}}/{{3}^{0}}$ amines, hence is used as a test to identify primary amines.