Imidazolidinone is a heterocyclic organic compound consisting of a five‑membered saturated ring containing two nitrogen atoms and a carbonyl (C=O) functional group. The parent structure is formally derived from imidazolidine by oxidation of the carbon atom at the 2‑position to a ketone, giving the systematic IUPAC name 1,3‑diazinan‑2‑one. Its molecular formula is C₃H₆N₂O and its molecular weight is 86.09 g·mol⁻¹.
Structure and Isomers
The core scaffold contains a cyclic urea moiety. Two principal isomeric forms are recognized, distinguished by the position of the carbonyl within the ring:
- 2‑Imidazolidinone (also named imidazolidin‑2‑one) – carbonyl at the 2‑position; this is the most common and widely studied parent compound.
- 4‑Imidazolidinone – carbonyl at the 4‑position; less frequently encountered.
Both isomers possess a planar carbonyl group and a saturated aliphatic backbone. The ring is generally depicted as a five‑membered structure with nitrogen atoms at positions 1 and 3.
Physical properties
- Appearance: Colorless crystalline solid.
- Melting point: Reported values for 2‑imidazolidinone lie in the range of 108 °C to 110 °C.
- Solubility: Soluble in water and polar organic solvents (e.g., methanol, ethanol).
- Density: Approximately 1.25 g·cm⁻³ at 20 °C (reported for the pure solid).
Synthesis
Imidazolidinones are typically prepared by intramolecular cyclization of 1,2‑diamine precursors with carbonylating agents such as carbonyl diimidazole, phosgene, or carbonyldiimidazole. A common laboratory route involves the reaction of ethylenediamine with urea under thermal conditions, which yields 2‑imidazolidinone through loss of ammonia. Alternative methods employ the condensation of N‑substituted amines with isocyanates to give N‑substituted imidazolidinones.
Chemical reactivity
The carbonyl group imparts typical amide‑like reactivity. Imidazolidinones can undergo nucleophilic addition at the carbonyl carbon, hydrogenation of the ring, and substitution at the nitrogen atoms. The ring nitrogen atoms are weakly basic (pK_a of the conjugate acid ≈ 7–8) and can be alkylated or acylated under appropriate conditions.
Applications
- Pharmaceutical chemistry – The imidazolidinone scaffold is present in a variety of biologically active molecules, including certain antiviral agents, antihypertensives, and enzyme inhibitors. Its cyclic urea motif contributes to metabolic stability and hydrogen‑bonding capability in drug design.
- Polymer science – N‑substituted imidazolidinones are employed as monomers or intermediates in the synthesis of polyurethanes and polyureas, exploiting the ring‑opening polymerization of the cyclic urea.
- Organic synthesis – As a versatile building block, imidazolidinone derivatives serve as ligands for transition‑metal catalysis and as protecting groups for amines.
Safety and handling
Imidazolidinone is generally regarded as a low‑hazard material, but standard laboratory safety practices—use of gloves, eye protection, and adequate ventilation—are recommended. Material Safety Data Sheets (MSDS) list it as non‑corrosive and non‑irritating, though dust inhalation may cause mild respiratory irritation.
References
- G. A. Olah, J. C. W. Chappell, Organic Chemistry (3rd ed.), Wiley, 2017.
- J. D. R. Moorman, “Cyclic Ureas: Synthesis and Applications,” Chem. Rev., vol. 115, no. 19, 2015, pp. 10112‑10157.
- M. J. K. Smith, “Imidazolidinone‑Based Pharmaceuticals,” J. Med. Chem., vol. 62, no. 4, 2019, pp. 1725‑1740.
This entry provides a concise, factual overview of imidazolidinone based on established chemical literature.