< b="" />Functional Groups< />

Functional groups are specific groups of atoms within organic compounds that are responsible for their characteristic chemical reactions and properties. They are essential in determining the reactivity and behavior of organic molecules. Here, we will discuss three functional groups and identify the one that is not a functional group.

< b="" />1. Carboxyl Group< />
The carboxyl group is a functional group consisting of a carbonyl group (C=O) and a hydroxyl group (OH) attached to the same carbon atom. It is denoted by -COOH or -CO2H. Carboxylic acids, such as acetic acid, are organic compounds that contain the carboxyl group. The carboxyl group is acidic in nature and can donate a proton, making carboxylic acids weak acids. It is involved in various reactions, including esterification and decarboxylation.

< b="" />2. Carbonyl Group< />
The carbonyl group is a functional group consisting of a carbon atom double-bonded to an oxygen atom (C=O). It is present in various organic compounds, such as aldehydes, ketones, carboxylic acids, and esters. The carbonyl group is highly polar due to the electronegativity difference between carbon and oxygen. It is responsible for many important reactions, including nucleophilic addition and oxidation.

< b="" />3. Isocyano Group< />
The isocyano group, also known as the isocyanide group, is a functional group consisting of a nitrogen atom triple-bonded to a carbon atom (N≡C). Isocyanides have a unique and unpleasant odor and are often used in organic chemistry as reagents or building blocks for the synthesis of various compounds. They are not commonly considered as functional groups because they do not exhibit the same characteristic reactivity and properties as other functional groups.

< b="" />4. Isocyanide< />
Isocyanide is not a functional group. It is a specific compound that contains the isocyano group. Isocyanides have the general formula R-N≡C, where R represents an organic substituent. Isocyanides are generally not stable and tend to react readily with various compounds, making them useful in organic synthesis.

In conclusion, the isocyano group is a functional group, while isocyanide is a compound containing the isocyano group. Therefore, option A (Isocyanide) is the correct choice as it is not a functional group.