<unk>  crystals Acidity The hydrogen centre in the carboxyl group (−COOH) in carboxylic acids such as<unk>  can separate from the molecule by ionization: :CH3COOH CH3CO2− + H+ Because of this release of the proton (H+),<unk>  has acidic character.<unk>  is a weak monoprotic acid. In aqueous solution, it has a pKa value of 4.76. Its conjugate base is acetate (CH3COO−). A 1.0 M solution (about the concentration of domestic vinegar) has a pH of 2.4, indicating that merely 0.4% of the<unk>  molecules are dissociated. However, in very dilute (−6 M) solution<unk>  is >90% dissociated. Deprotonation equilibrium of<unk>  in water Cyclic dimer of<unk> ; dashed green lines represent hydrogen bonds Structure In solid<unk> , the molecules form chains, individual molecules being interconnected by hydrogen bonds. In the vapour at , dimers can be detected. Dimers also occur in the liquid phase in dilute solutions in non-hydrogen-bonding solvents, and a certain extent in pure<unk> , but are disrupted by hydrogen-bonding solvents. The dissociation enthalpy of the dimer is estimated at 65.0–66.0 kJ/mol, and the dissociation entropy at 154–157 J mol−1 K−1. Other carboxylic acids engage in similar intermolecular hydrogen bonding interactions. Solvent properties Liquid<unk>  is a hydrophilic (polar) protic solvent, similar to ethanol and water. With a relative static permittivity (dielectric constant) of 6.2, it dissolves not only polar compounds such as inorganic salts and sugars, but also non-polar compounds such as oils as well as polar solutes. It is miscible with polar and non-polar solvents such as water, chloroform, and hexane. With higher alkanes (starting with octane),<unk>  is not miscible at all compositions, and solubility of<unk>  in alkanes declines with longer n-alkanes. The solvent and miscibility properties of<unk>  make it a useful industrial chemical, for example, as a solvent in the production of dimethyl terephthalate. Biochemistry At physiological pHs,<unk>  is usually fully ionised to acetate. The acetyl group, formally derived from<unk> , is fundamental to all forms of life. When bound to coenzyme A, it is central to the metabolism of carbohydrates and fats. Unlike longer-chain carboxylic acids (the fatty acids),<unk>  does not occur in natural triglycerides. However, the artificial triglyceride triacetin (glycerine triacetate) is a common food additive and is found in cosmetics and topical medicines.<unk>  is produced and excreted by<unk>  bacteria, notably the genus Acetobacter and Clostridium acetobutylicum. These bacteria are found universally in foodstuffs, water, and soil, and<unk>  is produced naturally as fruits and other foods spoil.<unk>  is also a component of the vaginal lubrication of humans and other primates, where it appears to serve as a mild antibacterial agent.
Acetic acid
Cefazolin
Cephalosporin
Nalidixic acid
Carbenicillin
Extended-spectrum penicillin
Resistin
Ciprofloxacin