Rigorously speaking the functional group is not the whole molecule but only that collection of atoms that provides a specific chemical function. For example, the chemical family of alcohols is characterized by the function of the hydroxyl (OH) group, and aldehydes, ketones are characterized by carbonyl groups (C=O). There are various combinations of hydroxyl groups in molecules along with carbonyl groups and these combinations can lead to hydroxyketones and aldehydes (the basis for sugars) as well as to carboxylic acids. Indeed, esters, and amides also have carbonyl groups (C=O) but differ in their combination with an additional structural feature. To understand the.
