Question

Which one of the following reductions with lithium aluminium hydride yield a secondary amine?
A.Nitroethane
B.Methyl isocyanide
C.Acetamide
D.Methyl cyanide

Answer 1

Hint: Alkyl isocyanide on reduction with lithium aluminium hydride forms a secondary amine containing methyl as one of the alkyl groups. It involves a catalytic reduction. Methyl isocyanide, also known as iso cyanomethane is an organic compound and a member of the isocyanide family and it is a colourless liquid.

Complete answer:
On catalytic reduction or with lithium aluminium hydride ($$LiAl{H}_4$$) or with the nascent hydrogen, alkyl isocyanide yields 2-degree amine whereas cyanide gives 1-degree amine on reduction.

Two hydrogen molecules are added across $$N\equiv C$$ triple bonds.

Therefore, the correct answer is option (B).

Note: Methyl isocyanide which is also known as iso cyanomethane, it is an organic compound and a member of the isocyanide family. It is a colourless liquid which is isomeric to methyl cyanide (acetonitrile), but its reactivity is very different. Its molar mass is 41.053 g/mole. Its Melting point is − $${45}^{0}C$$($-{49}^{0}F$; 228 K) The application of Methyl isocyanide is mainly for making 5-membered heterocyclic rings. The C-N distance in methyl isocyanide is very short, $$1.158\stackrel{0}{A}$$ as is characteristic of isocyanides. Methyl isocyanide was first prepared by A. Gautier by the reaction of silver cyanide with methyl iodide. The common method for preparing methyl isocyanides is by dehydrating N-methyl formamide. Many metal cyanides react with methylating agents to form complexes of methyl isocyanide. This type of reactivity has been invoked as being relevant to the origin of life.
Methyl isocyanide is very useful for the preparation of diverse heterocycles. It is often used to prepare transition metal isocyanide complexes.