Carboxylate

A carboxylate is the conjugate base of a carboxylic acid, R−COO⁻ (or R−CO−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.

Carboxylate ion. The dotted line means there is resonance.

RCOOH + NaOH → RCOONa + H2O

Examples

Some examples of carboxylates include;

• Formate, HCOO⁻
• Acetate, CH₃COO⁻
• Oxalate, (COO)2−2
• Citrate, C₃H₅O(COO)3−3