Question

Methyl isocyanide on reduction using LiAlH4 gives:
A. Methyl amine
B. Ethyl amine
C. Di methyl amine
D. Tri methyl amine

Answer 1

We have to remember that an isocyanide is an isomer of cyanide. Alkyl Isocyanides undergo either partial reduction or complete reduction depending upon the reagents used. Upon reduction they give n-methyl amines or so called secondary amines.

Complete step by step answer:
As we know that the alkyl group present in the isocyanide compound is a methyl group.
We know that in isocyanides, the alkyl group is bonded to the nitrogen atom of the compound cyanide. The chemical structure can be viewed as,

Image created in chemdraw by SME.
In the presence of reducing agent LiAlH4 the methyl isocyanide will reduce to form di methyl amine. The reaction can be written as,

Hence, the correct answer to the question is option C. di methyl amine.
Let us take a look at the other possible reactions of isocyanides.
Isocyanides undergo hydrolysis and form primary amines. For example, if we do hydrolysis of methyl isocyanide the resultant product will be methyl amine.

Likewise, if we do hydrolysis of ethyl cyanide the product will be ethyl amine.

So, the correct answer is Option B.

Note: As we know that the cyanides and isocyanides are isomers. In cyanide the bonding with other carbon chains is with carbon and in case of isocyanide the bonding with other carbon chains is with nitrogen. Alkyl cyanides and isocyanides are considered to be highly toxic compounds. Isocyanides have an unpleasant and strong odor. Isocyanides are hydrolysed by acids and not bases, because the carbon atom present in the compound is negatively charged and it attracts nucleophiles and not electrophiles. They are generally used for the formation of other compounds such as amines, amides, etc. In industries, dimethyl amines are produced by a catalytic process at high temperature and pressure from methanol and ammonia.