Methyl ester

A methyl ester of a carboxylic acid has the group $\mathrm{R}-\mathrm{C}(=\mathrm{O})-\mathrm{OC}{\mathrm{H}}_3$. The methyl group belongs to the alcohol-derived part of the ester.

Hydrolysis can regenerate a carboxylic acid and methanol. Changing a free acid into a methyl ester also changes charge and hydrogen-bonding behaviour, which can alter solubility and analytical handling.

Methyl butanoate is the ester $\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{C}(=\mathrm{O})\mathrm{OC}{\mathrm{H}}_3$. The four-carbon butanoyl group and one-carbon methyl group occupy different sides of the ester linkage.

Hydrolysis yields butanoic acid or butanoate together with methanol, depending on conditions. The carbonyl carbon remains part of the acid-derived fragment.

The dimethyl ester of benzene-1,2-dicarboxylic acid, with adjacent ester groups on a benzene ring.