Imidazolidinyl urea

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Imidazolidinyl urea
Imidazolidinyl urea correct formula.png
Imidazolidinyl urea erroneous formula.png
CAS number 39236-46-9 YesY=  YesY
PubChem 38258
ChemSpider 35067 YesY
EC number 254-372-6
ChEBI CHEBI:51805 YesY
Jmol-3D images Image 1
Image 2
Molecular formula C11H16N8O8
Molar mass 388.29 g/mol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Imidazolidinyl urea is an antimicrobial preservative used in cosmetics[citation needed]. It is chemically related to diazolidinyl urea which is used in the same way. Imidazolidinyl urea acts as a formaldehyde releaser.


Some people have a contact allergy to imidazolidinyl urea causing dermatitis.[1] Such people are often also allergic to diazolidinyl urea.


Imidazolidinyl urea was poorly characterized until recently and still has a wrong CAS structure assigned to it. New data show that the hydroxymethyl functional group of the imidazolidine ring is attached to the carbon, not the nitrogen atom:[2]

Imidazolidinyl urea (correct new structure) Imidazolidinyl urea (erroneous old structure)
Correct new structure Erroneous old structure


Imidazolidinyl urea is produced by the chemical reaction of allantoin and formaldehyde in the presence of sodium hydroxide solution and heat. The reaction mixture is then neutralized with hydrochloric acid and evaporated:

2 Allantoin + 3 H2C=O → Imidazolidinyl urea

Commercial imidazolidinyl urea is a mixture of different formaldehyde addition products including polymers.[2]


  1. ^ Review of toxicological data (NTP NIEHS)
  2. ^ a b Lehmann SV, Hoeck U, Breinholdt J, Olsen CE, Kreilgaard B. (2006). "Characterization and chemistry of imidazolidinyl urea and diazolidinyl urea". Contact Dermatitis 54 (1): 50–58. doi:10.1111/j.0105-1873.2006.00735.x. PMID 16426294.