= Carboxyl group
{title2=$\mathrm{-C(=O)OH}$}
A <carboxyl group> is the functional group $\mathrm{-C(=O)OH}$: one <carbon> has a <double bond> to <oxygen> and a single bond to a <hydroxyl group>. It gives a <carboxylic acid> its characteristic acid functionality. In <acetic acid>, the group is attached to a methyl group, giving $\mathrm{CH_3COOH}$.<Chemistry 2e by Paul Flowers and others>[§20.3, Carboxylic Acids and Esters]{ref}
Loss of the acidic hydrogen produces a <carboxylate>, the <conjugate base>:
$$
\mathrm{CH_3COOH\rightleftharpoons CH_3COO^-+H^+}.
$$
The <pH> influences the balance between these forms. A structural drawing of the neutral acid therefore need not show the predominant charge state in every solution. The <carboxyl group> is a part of the molecule, while <acetic acid> names the entire compound.
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