Alkyl halides do not show functional isomerism. Alcohols and ethers, aldehydes and ketones, cyanides and isocyanides are functional isomers.

Alkyl halides do not show functional isomerism. Alcohols and ethers, aldehydes and ketones, cyanides and isocyanides are functional isomers

Functional Group Isomerism

Functional group isomerism is a type of structural isomerism where compounds with the same molecular formula have different functional groups. In other words, the arrangement of atoms within the molecule is the same, but the functional group attached to the main carbon chain is different. This type of isomerism is possible in certain classes of organic compounds, but not in others.

Explanation:

Alcohols:
- Alcohols are organic compounds that have the functional group -OH (hydroxyl group) attached to a carbon atom.
- They can exhibit functional group isomerism because the position of the hydroxyl group can vary within the carbon chain.
- For example, the isomers of C4H10O are butanol (primary alcohol) and methylpropanol (secondary alcohol).

Aldehydes:
- Aldehydes have the functional group -CHO (aldehyde group) attached to a carbon atom.
- They can exhibit functional group isomerism because the position of the aldehyde group can vary within the carbon chain.
- For example, the isomers of C4H8O are butanal (aldehyde) and methyl ethyl ketone (ketone).

Alkyl Halides:
- Alkyl halides, also known as haloalkanes, are organic compounds that have a halogen atom (fluorine, chlorine, bromine, or iodine) attached to a carbon atom.
- They cannot exhibit functional group isomerism because the functional group remains the same (halogen atom) regardless of the position of the halogen atom within the carbon chain.
- For example, the isomers of C4H9Cl are 1-chlorobutane, 2-chlorobutane, 1,1-dichlorobutane, etc. but they do not exhibit functional group isomerism.

Cyanides:
- Cyanides have the functional group -CN (cyano group) attached to a carbon atom.
- They can exhibit functional group isomerism because the position of the cyano group can vary within the carbon chain.
- For example, the isomers of C3H5N are propionitrile and methyl cyanide.

Conclusion:
Functional group isomerism is not possible in alkyl halides because the functional group (halogen atom) remains the same regardless of its position within the carbon chain. However, it is possible in alcohols, aldehydes, and cyanides because the functional group (hydroxyl, aldehyde, and cyano groups, respectively) can vary in position within the carbon chain.