CH3CO2H

CH3CO2H, commonly known as acetic acid, is the chemical compound with the formula C2H4O2. It is a weak carboxylic acid and is a simple aliphatic mono-carboxylic acid. Its conjugate base is acetate. In aqueous solution it dissociates to give a pKa of about 4.76. Dilute acetic acid is the principal component of vinegar, typically around 4–8% by weight.

Acetic acid is a colorless liquid with a characteristic pungent odor. It has a boiling point of 118.1 °C and a melting point of 16.6 °C, and it is miscible with water and many organic solvents. The density is about 1.049 g/mL at room temperature. It is readily soluble in water and can form glacial (concentrated) acetic acid, which is typically around 99–100% purity.

Industrial production of acetic acid mainly proceeds via carbonylation of methanol with carbon monoxide, using rhodium or iridium catalysts (Monsanto or Cativa processes). The reaction yields acetic acid and water. Historically, acetic acid was obtained by oxidation of acetaldehyde. In nature, acetic acid is produced by fermentation and is the active component of vinegar.

Key applications of acetic acid include use as a solvent and chemical reagent, and as a building block for many derivatives. It is a precursor to vinyl acetate monomer (for polymers), cellulose acetate, and acetic anhydride. It is also employed as a preservative and acidity regulator in foods and as a catalyst or reagent in a variety of organic syntheses. Acetates are common salts formed from acetic acid and metals or amines.

Safety considerations: acetic acid is corrosive and can cause severe irritation to skin, eyes, and mucous membranes. It is flammable and should be handled with appropriate precautions.