5,5-Dimethylhydantoin

5,5-Dimethylhydantoin is a derivative of hydantoin having two methyl groups as substituents on the ring carbon. DMH can be used in silver electroplating baths as an alternative to cyanide. It is a degradation product of 1,3-dibromo-5,5-dimethylhydantoin that can be detected on foods that have not been properly washed. It can be easily produced by a Bucherer–Bergs reaction, warming a mixture of acetone cyanohydrin and ammonium carbonate.
Reaction of DMH with various halogens gives N,''N''-dihalo derivatives, such as, bromochloro-5,5-dimethylhydantoin, and dibromo-5,5-dimethylhydantoin, which can be used as reagents to supply of electrophilic halogen atoms or hypohalous acids. Sodium 4,4-dimethyl-2,5-dioxoimidazolidin-1-ide, the sodium salt of its conjugate base, has been commercialized as a stabilizer for active chlorine in the papermaking industry.