What functional group is associated with esters?

Esters are characterized by the presence of the functional group RCOOR'. This structure consists of a carbonyl group (C=O) bonded to an oxygen atom that is also bonded to an alkyl or aryl group (R'). The carbonyl part comes from a carboxylic acid and the alkyl part comes from the alcohol; hence, esters can be thought of as derived from the condensation reaction of these two types of compounds.

The general formula for an ester highlights this unique configuration: the R represents the hydrocarbon tail of the compound while the R' indicates the substituent that is connected via the oxygen. This distinct framework gives esters their characteristic properties, such as their pleasant aromas, which are often utilized in flavoring and fragrances.

In contrast, other functional groups listed do not match the defining structure of esters. For example, RCOOH represents carboxylic acids, R-NH2 indicates amines, and RCHO signifies aldehydes. Each of these functional groups possesses unique characteristics and reactivity that distinctly separates them from esters.