C2H3O2

C2H3O2, often written as C2H3O2−, is the acetate anion. It is the conjugate base of acetic acid (CH3COOH) and a common counterion in a wide range of salts such as sodium acetate, potassium acetate, and calcium acetate. Its nominal molar mass is 59.04 g/mol.

Structure and bonding: The acetate anion features a carboxylate group that is resonance-stabilized. The negative charge is delocalized over the two oxygens, resulting in two equivalent C–O bonds. The carboxylate unit is planar, with the carbonyl carbon in a trigonal planar geometry.

Occurrence and preparation: Acetate arises from deprotonation of acetic acid by a base. It is also produced industrially when acetic acid neutralizes with bases or forms salts with metals. In solution, acetate serves as a common buffering species in acetate buffers.

Properties: Acetate is a weak base. In water, it exists mainly as CH3COO−; the conjugate acid, acetic acid, has a pKa of about 4.76, giving a pKb for acetate around 9.24 at 25°C. Many acetate salts are soluble in water, with some variability among different metals.

Reactions and applications: As a nucleophile and base, the acetate ion participates in a range of reactions, including salt formation, esterifications, and acetyl transfer processes. In biochemistry and chemistry labs, acetate buffers are widely used to maintain pH near 4.75–5.0. In industry and food chemistry, acetates serve as buffering agents and as components of various salts (for example, sodium acetate in buffering and food processing).

Safety: Acetate salts are generally of low toxicity but should be handled according to standard laboratory safety practices, avoiding inhalation of powders and ingestion of large quantities.