What defines a carboxylic acid?

A carboxylic acid is defined by the presence of a functional group known as the carboxyl group, which is composed of a carbonyl group (a carbon atom double-bonded to an oxygen atom) linked to a hydroxyl group (an -OH group). This specific arrangement characterizes carboxylic acids and gives them their unique properties, such as being able to donate protons in solution, which contributes to their acidic nature.

Carboxylic acids are typically represented by the general formula RCOOH, where R can be a hydrogen atom or a hydrocarbon chain. This structure allows for the formation of a variety of different carboxylic acids, which can exhibit a range of physical and chemical properties.

The other options do not accurately define carboxylic acids. For instance, hydrocarbons with one triple bond refer to alkynes, which lack the specific functional groups that characterize carboxylic acids. Options that refer to compounds only containing nitrogen or strictly containing oxygen atoms do not fit the definition either, as carboxylic acids must include carbon as part of their essential structure.