Question

$C{{H}_{3}}N{{H}_{2}}+CHC{{l}_{3}}+KOH\to $
The nitrogen-containing compound formed is:
(A) \[C{{H}_{3}}-C\equiv N\]
(B) \[C{{H}_{3}}-NH-C{{H}_{3}}\]
(C) \[C{{H}_{3}}-{{N}^{-}}\equiv {{C}^{+}}\]
(D) \[C{{H}_{3}}-{{N}^{+}}\equiv {{C}^{-}}\]

Answer 1

Hint: According to carbylamine reaction which is based on electrophiles, when a primary amine is heated with chloroform in the presence of alcoholic potassium hydroxide, then the reaction tends to form a product i.e. isocyanide or a carbylamine.

Complete step by step solution:
Due to the presence of lone pair of electrons on the nitrogen atom, animes like ammonia are good nucleophiles and hence react with a variety of electrophiles (electron-deficient compounds) such as metal ions, acid halides like acid chlorides, acid anhydrides like chloroform, etc.
When a primary amine is reacted with chloroform, the reaction is called a “carbylamine reaction” as a carbylamine or isocyanide is formed as a product. This reaction is also used as an isocyanide test.
According to this reaction, both aliphatic and aromatic primary amines when warmed with chloroform and an alcoholic solution of \[KOH\], it produces an isocyanide or a carbylamine which will have a very unpleasant smell.
When primary amine reacts with chloroform, it forms an alkyl isocyanide. The general reaction is shown below,
\[R-N{{H}_{2}}+CHC{{l}_{3}}+3KOH\xrightarrow{Heat}R-N\equiv C+3KCl+3{{H}_{2}}O\]
As per the given question, methylamine (a primary amine) with chemical formula \[C{{H}_{3}}N{{H}_{2}}\], is being reacted with chloroform i.e. \[CHC{{l}_{3}}\]and potassium hydroxide i.e. \[KOH\]. Hence, it will form methyl isocyanide with three moles of potassium chloride and three moles of water. This can be understood by the following balanced chemical reaction shown,
\[C{{H}_{3}}N{{H}_{2}}+CHC{{l}_{3}}+KOH\to C{{H}_{3}}-{{N}^{+}}\equiv {{C}^{-}}+3KCl+3{{H}_{2}}O\]
So, the product formed is \[C{{H}_{3}}-{{N}^{+}}\equiv {{C}^{-}}\].

Hence, the correct option is D.

Additional information:
The carbylamine reaction is not given by secondary and tertiary amines (both aliphatic and aromatic compounds). Therefore, it is used to distinguish primary amines from secondary and tertiary amines.

Note: The possible mistake is, you may get confused between options C and D because their chemical formulas are the same but the difference is, they are having different bonding. This reaction is a specific type of reaction which forms the only isocyanide. So, while writing the reaction, keep in mind that by-products should be correct.