Hypohalites

Hypohalites are a family of chemical species that contain a halogen bound to one oxygen and bearing a negative charge, with the general formula XO−. They are the conjugate bases of hypohalous acids HOX, where X is a halogen. The most common members are hypochlorite (ClO−), hypobromite (BrO−), and hypoiodite (IO−).

In aqueous solution, hypohalites exist in equilibrium with their corresponding hypohalous acids HOX. The acids are weak, with HOCl having a pKa around 7.5, HOBr around 8.7, and HOI around 10.5. At pH above these values, XO− predominates; at lower pH, HOX becomes more prevalent. Hypohalites are strong oxidants and tend to decompose gradually, with stability depending on pH, temperature, and concentration.

Hypochlorite is widely used in disinfection and bleaching. Sodium hypochlorite solutions are common in household bleach and water treatment. Hypobromite and hypoiodite occur less commonly in consumer products but are encountered in chemical synthesis and in certain biological contexts where oxidizing activity is relevant.

Preparation and reactions: hypohalites can be formed by oxidizing halide ions in basic solution, typically by reacting halide with chlorine or other oxidants, or by electrolysis of halide-containing solutions. They readily oxidize organic substrates, decolorize dyes, and can participate in halogenation under suitable conditions. Hypohalites can disproportionate to halates (XO3−) and halides (X−), for example 3 ClO− → ClO3− + 2 Cl−, a process influenced by pH and temperature.

Safety: hypohalites are corrosive, reactive oxidants that can release chlorine gas when acidified and pose hazards to skin, eyes, and respiratory systems. They should be handled with care, stored away from incompatible materials, and used in appropriate concentrations.