What is the formula for an ester functional group?

An ester functional group has the general formula RCOOR, where R represents alkyl or aryl groups. In this structure, the 'C' is a carbonyl carbon (C=O) that is bonded to an oxygen atom, which in turn is linked to another carbon (the 'R' group). This arrangement defines the unique characteristics of esters, which are derived from the reaction of an alcohol and a carboxylic acid.

The ester linkage occurs when the hydroxyl group (-OH) of the carboxylic acid is replaced by an alkoxy group (-O-R), resulting in the formation of the ester bond. This functional group is commonly found in various natural and synthetic compounds, contributing to their properties such as aroma and flavor in food and fragrances.

The other options listed do not represent ester functional groups: C6H5 is a phenyl group (derived from benzene), PO4 3- is a phosphate group, and CHO represents an aldehyde functional group. Each of these has distinct structural characteristics and is involved in different chemical behaviors and reactions. Understanding the specific structure of esters (RCOOR) is crucial for recognizing their role in biochemistry and organic chemistry.