BCDMH explained

1-Bromo-3-chloro-5,5-dimethylhydantoin (BCDMH or bromochlorodimethylhydantoin) is a chemical structurally related to hydantoin. It is a white crystalline compound with a slight bromine and acetone odor and is insoluble in water, but soluble in acetone.

BCDMH is an excellent source of both chlorine and bromine as it reacts slowly with water releasing hypochlorous acid and hypobromous acid. It used as a chemical disinfectant for recreational water sanitation and drinking water purification.^[1] BCDMH works in the following manner:^[2]

The initial BCDMH reacts with water (R = Dimethylhydantoin):

BrClR + 2 H₂O → HOBr + HOCl + RH₂

Hypobromous acid partially dissociates in water:

HOBr → H⁺ + OBr⁻

Hypobromous acid oxidizes the substrate, itself being reduced to bromide:

HOBr + Live pathogens → Br⁻ + Dead pathogens

The bromide ions are oxidized with the hypochlorous acid that was formed from the initial BCDMH:

Br⁻ + HOCl → HOBr + Cl⁻

This produces more hypobromous acid; the hypochlorous acid itself act directly as a disinfectant in the process.

Preparation

This compound is prepared by first brominating, then chlorinating 5,5-dimethylhydantoin:

External links

Notes and References

Web site: NSF/ANSI 60 - Drinking Water Treatment Chemicals - Health Effects. November 14, 2018. NSF International. NSF International. 2012. NSF Product and Service Listings. NSF International. Bromochlorodimethylhydantoin[CL] - Bromicide Tablets - Algicide - Disinfection & Oxidation. [CL] The residual levels of chlorine (hypochlorite ion and hypochlorous acid), chlorine dioxide, chlorate ion, monochloramine and disinfection by-products shall be monitored in the finished drinking water to ensure compliance to all applicable regulations..
South Australian Health Commission, "Standard for the Operation of Swimming Pools and Spa Pools in South Australia", Supplement C: Bromine Disinfection, page 8. Retrieved on 2009-05-12.