hypokloroosihapon

Hypochlorous acid, with the chemical formula HOCl, is a weak acid and a powerful oxidizing agent used as a disinfectant and antiseptic. In water, chlorine dissolves and partially hydrolyzes to form HOCl and hydrochloric acid: Cl2 + H2O ⇌ HOCl + HCl. Hypochlorous acid can further dissociate to hydrogen ions and hypochlorite: HOCl ⇌ H+ + OCl−, with a pKa around 7.5 at 25°C. At pH values below about 7.5, HOCl is the dominant species and is typically more effective as a disinfectant than the hypochlorite anion (OCl−).

Biological relevance: HOCl is produced by immune cells, notably neutrophils and macrophages, via the enzyme myeloperoxidase, which catalyzes the reaction H2O2 + Cl− → HOCl + H2O. This reactive species contributes to the destruction of engulfed microbes by oxidizing essential cellular components.

Applications: Hypochlorous acid is widely used in water treatment, sanitation, disinfection of surfaces, food processing, and some wound-care products. It is often generated in situ by acidifying sodium hypochlorite solutions or by controlled chlorine gas dissolution, yielding solutions enriched in HOCl that are effective at neutral pH. The antimicrobial efficacy of HOCl depends on concentration, exposure time, temperature, and the presence of organic matter, which can consume HOCl and form disinfection byproducts.

Safety and stability: HOCl is corrosive and can irritate skin, eyes, and the respiratory tract at sufficient concentrations. It degrades over time, especially under light and in the presence of metals, to chloride and oxygen. Reaction with organic matter can produce disinfection byproducts, so proper handling, ventilation, and concentration control are important. Mixing HOCl with ammonia or acidic solutions can release chlorine gas, a hazardous exposure risk.