1. 5,5-Dimethylhydantoin (CAS 77-71-4): An Overview
5,5-Dimethylhydantoin (CAS 77-71-4), also known as DMH, is a white crystalline heterocyclic compound belonging to the hydantoin family. Its core is an imidazolidine-2,4-dione ring – a five-membered ring containing two nitrogen atoms and two carbonyl groups – carrying two methyl groups at the 5-position. The molecular formula is C5H8N2O2 and the molecular weight is 128.13 g/mol.
Although 5,5-dimethylhydantoin is sometimes discussed as if it were itself a disinfectant or preservative, its commercial importance is primarily as a key intermediate and building block. The reactive N-H groups of the hydantoin ring make it easy to derivatise, and two derivative families dominate its downstream use: halogenated hydantoins (such as DCDMH and DBDMH) used as disinfectants and bleaching agents, and dimethylol (DMDMH) derivatives used as formaldehyde-releasing preservatives. It is also a starting point for fine-chemical, pharmaceutical and agrochemical synthesis.
This article reviews the chemistry, structure, manufacturing route, specifications, downstream products and handling of 5,5-dimethylhydantoin from the perspective of a supplier and industrial user.
2. Chemical Identity and Physicochemical Properties
| Property | Value |
|---|---|
| Chemical name (IUPAC) | 5,5-Dimethylimidazolidine-2,4-dione |
| Common names | 5,5-Dimethylhydantoin; DMH; dimethylhydantoin |
| CAS Registry Number | 77-71-4 |
| Molecular formula | C5H8N2O2 |
| Molecular weight | 128.13 g/mol |
| Appearance | White crystalline powder |
| Melting point | About 174 – 181 °C |
| Solubility | Limited solubility in water; more soluble in some polar organic solvents |
| Functional groups | Two amide (N-H) groups and two ring carbonyls; a gem-dimethyl-substituted carbon |
| PubChem CID | 6491 |
The isomeric SMILES notation of the molecule is:
CC1(C(=O)NC(=O)N1)C
Two features define the chemistry. First, the two N-H groups are nucleophilic and can be alkylated, halogenated or hydroxymethylated under straightforward conditions – the basis for essentially all of the important downstream derivatives. Second, the two ring carbonyls make the molecule susceptible to hydrolysis under strong acidic or basic conditions, which can open the ring to the corresponding amino acid.
3. The Hydantoin Ring: Structure and Reactivity
Hydantoin is the common name for the imidazolidine-2,4-dione ring system – a five-membered ring with nitrogen at positions 1 and 3 and carbonyl groups at positions 2 and 4. In 5,5-dimethylhydantoin, the two hydrogens at position 5 are replaced by methyl groups. This substitution has two practical consequences: it makes the ring carbon quaternary and more sterically protected, and it increases the crystallinity and thermal stability of the solid.
The reactivity that matters commercially comes from the nitrogen atoms, and it falls into three families:
| Reaction | Reagent | Product family |
|---|---|---|
| N-Halogenation | Chlorine or bromine sources (e.g. hypochlorite, chlorine, bromine) | 1,3-Dihalo-5,5-dimethylhydantoins (DCDMH, DBDMH) |
| N-Hydroxymethylation | Formaldehyde | Dimethylol derivatives such as DMDMH |
| Hydrolysis (ring opening) | Strong acid or base | Corresponding amino acid derivatives |
These three reactions explain why a relatively simple molecule occupies such a central place in the disinfectant, preservative and fine-chemical industries.
4. Manufacturing: The Bucherer-Bergs Route
Commercial 5,5-dimethylhydantoin is produced by the Bucherer-Bergs reaction, in which a ketone is converted directly into a 5,5-disubstituted hydantoin using hydrogen cyanide and ammonium carbonate.
4.1 The main route
For 5,5-dimethylhydantoin the ketone is acetone. The reaction combines acetone, hydrogen cyanide and ammonium carbonate (which supplies both ammonia and carbon dioxide) in aqueous or aqueous-alcoholic medium, giving the hydantoin ring directly:
Acetone + HCN + (NH4)2CO3 → 5,5-Dimethylhydantoin
Mechanistically the ketone first adds cyanide to give a cyanohydrin, which then reacts with ammonia and carbon dioxide to form the ring. The Bucherer-Bergs route is valued because it builds the complete hydantoin ring in a single sequence from cheap, readily available raw materials.
4.2 Related variants
A closely related approach starts from acetone cyanohydrin rather than acetone and hydrogen cyanide separately, then adds ammonia and carbon dioxide. Both routes converge on the same hydantoin, and the choice between them is a matter of raw-material sourcing, safety engineering and process economics, since hydrogen cyanide handling is a significant design consideration.
4.3 Finishing
Whichever variant is used, the crude product is isolated, purified by crystallisation and dried to give the white crystalline powder of commerce. Melting point, drying loss, ash content and colour are the parameters that confirm the quality of the finished material.
4.4 Route comparison
| Route | Key raw materials | Notes |
|---|---|---|
| Bucherer-Bergs (from acetone) | Acetone, HCN, ammonium carbonate | The standard industrial route; builds the ring in one sequence |
| From acetone cyanohydrin | Acetone cyanohydrin, ammonia, CO2 | Related variant; same end product |
| Derivatisation routes (downstream, not DMH manufacture) | DMH + halogen or formaldehyde | Produces DCDMH/DBDMH and DMDMH respectively |
5. Grades and Specifications
5,5-Dimethylhydantoin is supplied as a crystalline solid. A typical commercial specification is shown below; the same parameters are what a buyer will see on the Certificate of Analysis.
| Parameter | Specification |
|---|---|
| Appearance | White crystal powder |
| Purity (assay) | 99% min |
| Melting point | 174 – 181 °C |
| Drying loss | 0.5% max |
| Ash content | 0.2% max |
| Colour (APHA) | 10 max |
For downstream users, the purity and the melting point are the most informative figures: a tight melting range confirms a well-crystallised, single product with low residual solvent and by-product content, while the ash and colour limits guard against inorganic and coloured impurities that could carry into a biocide or preservative.
6. Downstream Products: Halogenated Hydantoin Biocides
The largest and most important use of 5,5-dimethylhydantoin is as the starting material for halogenated hydantoins. Reacting DMH with a chlorine or bromine source at the two N-H positions gives 1,3-dihalo-5,5-dimethylhydantoins, above all:
- DCDMH – 1,3-dichloro-5,5-dimethylhydantoin, a chlorine-release disinfectant and bleach activator.
- DBDMH – 1,3-dibromo-5,5-dimethylhydantoin, a bromine-release disinfectant and oxidising agent.
These derivatives are the “active” articles that many buyers know by name: they are used as disinfectants, sanitisers and bleaching agents in swimming-pool and spa water, industrial and cooling water, and in a range of industrial bleaching and antimicrobial applications. When dissolved, they release active halogen in a controlled way, which is what makes them convenient and safer to handle than elemental halogen.
The relationship is worth stating plainly because it is often blurred: DMH is the precursor. The antimicrobial activity in these applications comes from the halogenated derivative, not from 5,5-dimethylhydantoin itself. That is the core of the market for DMH.
7. Downstream Products: DMDMH and Formaldehyde-Releasing Preservatives
The second major downstream family comes from N-hydroxymethylation. Reacting DMH with formaldehyde gives 1,3-dimethylol-5,5-dimethylhydantoin (DMDMH), a widely used preservative.
DMDMH works by slowly releasing formaldehyde, which provides antimicrobial protection, and it is used to preserve a range of water-based and industrial products where microbial growth must be controlled. Because it releases formaldehyde gradually, it is formulated and regulated carefully, but it remains an established preservative chemistry.
As with the halogenated family, the distinction matters: 5,5-dimethylhydantoin itself is not the formaldehyde-releasing preservative – it is the hydantoin backbone on which the dimethylol preservative is built. DMH’s value lies in providing a stable, crystalline, easy-to-derivatise scaffold for both the halogenated and the dimethylol families.
8. Other Uses: Pharmaceutical and Specialty Intermediates
Beyond the two large derivative families, 5,5-dimethylhydantoin is used as a building block in more specialised chemistry.
- Amino acid and pharmaceutical intermediates. Hydrolysis of the hydantoin ring opens it to the corresponding amino acid, a transformation that is exploited in the synthesis of amino acids and related pharmaceutical intermediates.
- Agrochemical intermediates. Hydantoin derivatives serve as intermediates in the manufacture of certain crop-protection and specialty chemicals.
- Specialty derivatives. The N-H groups allow DMH to be incorporated into a range of functional molecules – for example phosphorus-containing derivatives studied as flame-retardant intermediates, and other tailor-made fine chemicals.
These uses are smaller in volume than the biocide and preservative families, but they draw on the same property: a rigid, stable, easily functionalised hydantoin core.
9. Application Summary
| Application | DMH’s role | Key derivative / product |
|---|---|---|
| Water and pool disinfection | Precursor | DCDMH, DBDMH (chlorine/bromine release) |
| Bleaching and sanitising | Precursor | Halogenated hydantoins |
| Preservation of water-based products | Precursor | DMDMH (formaldehyde release) |
| Amino acid and pharma intermediates | Building block | Hydantoin hydrolysis products |
| Agrochemical intermediates | Building block | Various derivatives |
| Specialty / flame-retardant intermediates | Building block | Phosphorus-containing derivatives |
10. Handling, Safety and Storage
5,5-Dimethylhydantoin is a solid fine chemical and should be handled with the normal precautions used for organic powders: avoid generating and inhaling dust, use appropriate gloves and eye protection, and work in a well-ventilated area.
- Storage. Keep in a dry, sealed container at ambient temperature, protected from moisture and away from strong acids, bases and oxidising agents, which could react with the amide groups.
- Thermal behaviour. The material is thermally stable under normal conditions; like most nitrogen-containing organics, it can release nitrogen oxides and carbon monoxide if it is decomposed by excessive heat or fire.
- Derivatisation safety. Users who convert DMH into halogenated or hydroxymethylated derivatives should note that those downstream reactions involve halogens or formaldehyde and require their own dedicated safety controls. DMH itself is the safer form to store and transport.
The safety data sheet (SDS) should be consulted for full hazard, first-aid and transport information, and local regulations should be observed.
11. Procurement: Packaging, Documentation and Selection
| Consideration | What to confirm |
|---|---|
| Assay | Usually 99% min, as stated on the COA |
| Melting point | A tight range (about 174 – 181 °C) indicating a well-crystallised product |
| Drying loss / moisture | 0.5% max, to limit moisture uptake in storage |
| Ash content | 0.2% max, to limit inorganic residues |
| Colour (APHA) | 10 max, important where the derivative must meet a colour specification |
| Packaging | 25 kg fibre drums or bags as agreed; sealed against moisture |
| Documentation | Certificate of Analysis and SDS; additional documents on request |
| Storage and shelf life | Dry, sealed, ambient storage; retest period per COA |
Because DMH is normally converted into a derivative downstream, buyers should confirm that the specifications that matter for their derivative – above all assay, colour and residual moisture – are met consistently from lot to lot.
12. Frequently Asked Questions
What is 5,5-dimethylhydantoin?
5,5-Dimethylhydantoin (CAS 77-71-4, C5H8N2O2) is a white crystalline hydantoin derivative with two methyl groups at the 5-position. It is used mainly as an intermediate for halogenated hydantoin biocides and for formaldehyde-releasing preservatives.
Is 5,5-dimethylhydantoin itself a disinfectant?
No – not in the usual sense. It is the precursor. The antimicrobial and bleaching activity in water-treatment and pool applications comes from its halogenated derivatives, such as DCDMH and DBDMH. Likewise, the formaldehyde-releasing preservative is the dimethylol derivative DMDMH, not DMH itself.
How is 5,5-dimethylhydantoin manufactured?
It is produced by the Bucherer-Bergs reaction, in which acetone, hydrogen cyanide and ammonium carbonate are combined to build the hydantoin ring in a single sequence. A closely related variant starts from acetone cyanohydrin.
What are the main downstream products of DMH?
Two families dominate: 1,3-dihalo-5,5-dimethylhydantoins (DCDMH and DBDMH) used as disinfectants and bleaching agents, and 1,3-dimethylol-5,5-dimethylhydantoin (DMDMH) used as a formaldehyde-releasing preservative.
What is the melting point and purity?
The commercial product is a white crystal powder with a melting point of about 174 – 181 °C and a purity of 99% min, with drying loss 0.5% max, ash 0.2% max and colour (APHA) 10 max.
Why is 5,5-dimethylhydantoin a useful intermediate?
Because its two N-H groups are easy to functionalise, it can be halogenated, hydroxymethylated or otherwise derivatised under straightforward conditions, giving access to biocides, preservatives and fine chemicals from one stable, crystalline scaffold.
Can 5,5-dimethylhydantoin be used to make amino acids?
Yes. Hydrolysis of the hydantoin ring opens it to the corresponding amino acid, which is why hydantoins are used as intermediates in amino acid and pharmaceutical synthesis.
How should 5,5-dimethylhydantoin be stored?
In a dry, sealed container at ambient temperature, protected from moisture and kept away from strong acids, bases and oxidising agents. Packaging is typically 25 kg drums or bags as agreed.
Where can I buy 5,5-dimethylhydantoin?
PolyBlueChem supplies 5,5-Dimethylhydantoin (CAS 77-71-4) as a 99% min crystalline powder with COA and SDS. Contact our team for specifications, packaging and a quotation.
What should a buyer check on the COA?
Assay (99% min), melting point, drying loss, ash content and colour (APHA). Where the material will be converted into a derivative, assay and colour consistency from lot to lot are particularly important.
13. References and Further Reading
- PubChem Compound Summary, 5,5-Dimethylhydantoin, CID 6491 (National Library of Medicine).
- Standard references on the Bucherer-Bergs hydantoin synthesis.
- Manufacturer technical literature on halogenated hydantoin disinfectants and on DMDMH preservatives.
Disclaimer: This article is provided for technical and informational reference only and does not constitute medical, regulatory or legal advice. It describes 5,5-dimethylhydantoin as an industrial intermediate; it does not describe clinical uses, and it does not describe how to formulate or use downstream disinfectants or preservatives, which are subject to their own regulations.
PolyBlueChem supplies 5,5-Dimethylhydantoin (CAS 77-71-4) with a full Certificate of Analysis. For specifications, a quotation or documentation, contact our team. See also our guide to how to buy 5,5-dimethylhydantoin.