1. Basic Identification Information

Parameter	English Specification/Value
IUPAC Name	5,5-Dimethylimidazolidine-2,4-dione (also: 5,5-Dimethyl-2,4-imidazolidinedione)
Common Name(s)	5,5-Dimethylhydantoin; DMH; Dimethylhydantoin; Hydantoin, 5,5-dimethyl-; Dantoin DMH
CAS Registry Number	77-71-4
EC/EINECS Number	200-51-3
Molecular Formula	C₅H₈N₂O₂
Molecular Weight	128.13 g/mol
Chemical Class	Cyclic urea; imidazolidinedione derivative; organic synthesis intermediate; polymer building block
Related Compound	Hydantoin (CAS 461-72-3) (parent compound without methyl substitutions; higher solubility but lower thermal stability)

2. Physicochemical Properties

Property Category	Specific Parameter	Specification/Value
Structural Features	Functional Groups	Cyclic structure with two carbonyl groups (C=O at C2 and C4), two NH groups (at N1 and N3), and two methyl groups (-CH₃) at C5; symmetric dimethyl substitution enhances thermal stability
Physical Appearance	State & Color	White to off-white crystalline powder; odorless or faint urea-like odor; bitter taste
	Melting Point	174–177 °C (lit., decomposes above 280 °C)
	Boiling Point	Decomposes before boiling (releases CO₂ and methylamine vapors above 280 °C)
	Density (25 °C)	1.10 ± 0.1 g/cm³ (crystalline form)
Solubility	Polar Solvents	Slightly soluble in water (≈2 g/100 mL at 25 °C; increases to 10 g/100 mL at 80 °C); soluble in methanol (15 g/100 mL), ethanol (8 g/100 mL), and dimethylformamide (25 g/100 mL)