Carboxylic Acid Ester
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R1 = H, alkyl, aryl
R2 = alkyl, aryl
eg:
The O=C—O group in a carboxylic acid ester is called the carboxylic acid ester group.
Carboxylic acid esters are the most common esters in organic chemistry. The term ester used without a qualifier usually means a carboxylic acid ester and the term ester group a carboxylic acid ester group.