Final answer:
The carbon attached to the carboxyl group in molecules gives them the name carboxylic acid, which is a functional group represented as -CO₂H. so, option 3 is the correct answer.
Step-by-step explanation:
The carbon attached to the carboxyl group is the functional group that gives these molecules the name carboxylic acid. This group consists of a carbon double-bonded to oxygen, and also bonded to a hydroxyl group (OH), represented as -CO₂H. This distinctive structure separates carboxylic acids from aldehydes, ketones, and esters, which also contain the carbonyl group but have different bonding arrangements around the carbonyl carbon. Aldehydes have at least one hydrogen attached to the carbonyl carbon, while ketones have two carbon groups attached. Esters contain the -CO₂R group, where R is an alkyl or aryl group.
The carbon attached to the carboxyl group is the functional group that gives these molecules the name carboxylic acid. Carboxylic acids are organic compounds that contain the -CO₂H group as their functional group. In a carboxylic acid, the carbon atom of the carboxyl group is bonded to a hydrogen and to an oxygen that is double-bonded to another oxygen.