Carboxylate

Carboxylate ion. The dotted line means there is resonance.

A carboxylate is the conjugate base of a carboxylic acid, RCOO− (or RCO−2). It is an ion with negative charge. Carboxylate ions are made when a carboxylic acid loses a hydrogen ion. Such acids usually have pKa of less than 5, meaning that many bases, such as sodium hydroxide or sodium bicarbonate can remove the hydrogen ions from them.

RCOOH + NaOH → RCOONa + H2O

Examples

Some examples of carboxylates include;

• Formate ion, HCOO−
• Acetate ion, CH3COO−
• Methanetetracarboxylate ion, C(COO−)4
• Oxalate ion, (COO)2−