**Isomerism exhibited by alkyl cyanide and alkyl isocyanide is functional isomerism.**

**Functional isomerism:**
Functional isomerism is a type of isomerism in which compounds have the same molecular formula but differ in the functional group they contain. In other words, functional isomers have different functional groups attached to the same carbon skeleton.

**Alkyl cyanide and alkyl isocyanide:**
Alkyl cyanide and alkyl isocyanide are examples of functional isomers. They have the same molecular formula, but differ in the arrangement of atoms within the molecule.

**Alkyl cyanide (nitrile):**
Alkyl cyanides, also known as nitriles, have the functional group -CN (cyano group) attached to the carbon skeleton. The carbon atom in the cyano group is sp hybridized, and the nitrogen atom is sp hybridized. The general formula for alkyl cyanides is R-C≡N, where R represents an alkyl group.

**Alkyl isocyanide (isocyanide):**
Alkyl isocyanides, also known as isocyanides, have the functional group -NC (isocyanide group) attached to the carbon skeleton. The carbon atom in the isocyanide group is sp hybridized, and the nitrogen atom is sp hybridized. The general formula for alkyl isocyanides is R-N≡C, where R represents an alkyl group.

**Difference between alkyl cyanide and alkyl isocyanide:**
The main difference between alkyl cyanide and alkyl isocyanide is the location of the nitrogen atom in the molecule. In alkyl cyanide, the nitrogen atom is attached to the carbon skeleton by a triple bond, whereas in alkyl isocyanide, the nitrogen atom is attached to the carbon skeleton by a single bond.

**Example:**
An example of alkyl cyanide is ethanenitrile (acetonitrile), CH3CN, where the cyano group is attached to the carbon skeleton.
An example of alkyl isocyanide is ethyl isocyanide, CH3NC, where the isocyanide group is attached to the carbon skeleton.

**Conclusion:**
Therefore, alkyl cyanide and alkyl isocyanide exhibit functional isomerism because they have the same molecular formula but different functional groups attached to the carbon skeleton.

The major difference is, in cyanide bonding of alkyl takes place though carbon whereas in isocyanide , bonding of alkyl takes place through nitrogen. Both -CN and -NC are functional isomers as they have same molecular formula but differ in functional group.