CH3COO

CH3COO is the acetate moiety, most commonly encountered as the acetate ion CH3COO−, the conjugate base of acetic acid (CH3COOH). It is a two-carbon carboxylate unit in which a methyl group is attached to a carboxylate, giving a planar, resonance-stabilized group with the negative charge delocalized over the two oxygen atoms.

As a chemical fragment, CH3COO appears in salts and esters. Salts such as sodium acetate, potassium acetate, and calcium acetate are common reagents and buffering agents. In organic synthesis, the CH3COO fragment is part of acetate esters, where the acetyl group is bound to an alkoxy moiety (for example methyl acetate, CH3COOCH3).

Acetic acid has a pKa of approximately 4.76, making CH3COO− a relatively weak base. In aqueous solution, acetate participates in acid–base equilibria and can form acetate buffers when combined with acetic acid, typically stabilizing pH around 4.75. The base behavior is quantified by a small Kb (~5.6×10−10), reflecting limited basicity of the acetate ion.

Applications and presence: acetate salts are widely used in laboratories, industry, and food processing (for example, as buffering agents or preservatives; sodium acetate is also used in the food additive E262). The acetate group also features prominently in esters and acyl transfer reactions, and in biochemistry, acetate can be activated to acetyl-CoA in metabolic pathways.

Safety and handling are generally moderate; acetate salts are typically low in toxicity but should be handled according to standard chemical hygiene practices.