Esters

Esters (R-CO-O-R’) are named as alkyl derivatives of carboxylic acids. The alkyl (R’) group is named first. The R-CO-O part is then named as a separate word based on the carboxylic acid name, with the ending changed from -oic acid to -oate. For example, CH₃CH₂CH₂CH₂COOCH₃ is methyl pentanoate, and (CH₃)₂CHCH₂CH₂COOCH₂CH₃ is ethyl 4-methylpentanoate. For esters such as ethyl acetate (CH₃COOCH₂CH₃), ethyl formate (HCOOCH₂CH₃) or dimethyl phthalate that are based on common acids, IUPAC recommends use of these established names, called retained names. The -oate changes to -ate. Some simple examples, named both ways, are shown in the figure above.

If the alkyl group is not attached at the end of the chain, the bond position to the ester group is infixed before “-yl”: CH₃CH₂CH(CH₃)OOCCH₂CH₃ may be called but-2-yl propanoate or but-2-yl propionate.