The urea molecule adopts a planar conformation within its crystalline state. When in the gas phase under minimum-energy conditions, nitrogen atoms take on pyramidal geometry.
In solid urea, the oxygen atom forms two N-H-O hydrogen bonds, constructing a compact, thermodynamically stable hydrogen-bond network. This bonding arrangement yields an open structural framework consisting of molecular ribbons that shape square cross-section tunnels, despite slight compromises to tight molecular stacking.
The carbon atom of urea features sp² hybridization. Its C-N bonds display distinct double-bond characteristics, and the carbonyl oxygen demonstrates stronger basicity compared with carbonyl oxygen present in formaldehyde and similar substances. Benefiting from its capacity to generate abundant hydrogen bonds with water molecules, urea achieves outstanding water solubility.
Urea Chemical Properties
| Melting point | 132-135 °C(lit.) |
| Boiling point | 332.48°C (estimate) |
| density | 1.335 g/mL at 25 °C(lit.) |
| vapor pressure | <0.1 hPa (20 °C) |
| refractive index | n20/D 1.40 |
| storage temp | 2-8°C |
| solubility | H2O: 8 M at 20 °C |
| form | powder |
| pka | 0.10(at 25℃) |
| color | white |
| Specific Gravity | 1.335 |
| Odor | almost odorless |
| PH | 8.0-10.0 (20℃, 8M in H2O) |
| Water Solubility | 1080 g/L (20 ºC) |
| λmax | λ: 260 nm Amax: 0.03 λ: 280 nm Amax: 0.02 |
| Merck | 14,9867 |
| BRN | 635724 |
| Dielectric constant | 3.5（Ambient） |
| Stability | Substances to be avoided include strong oxidizing agents. Protect from moisture. |
| InChIKey | XSQUKJJJFZCRTK-UHFFFAOYSA-N |
| LogP | -1.660 (est) |
| CAS DataBase Reference | 57-13-6(CAS DataBase Reference) |
| NIST Chemistry Reference | Urea(57-13-6) |
| EPA Substance Registry System | Urea (57-13-6) |
Safety Information
| Hazard Codes | Xn,Xi |
| Risk Statements | 36/37/38-40-38 |
| Safety Statements | 26-36-24/25-37 |
| RIDADR | Not regulated |
| WGK Germany | 1 |
| RTECS | YR6250000 |
| TSCA | Yes |
| HS Code | 31021010 |
| Hazardous Substances Data | 57-13-6(Hazardous Substances Data) |
| Toxicity | LD50 orally in Rabbit: 8471 mg/kg LD50 dermal Rat 8200 mg/kg |
Urea serves as a key physiological substance for nitrogen metabolism in mammals. Produced in the liver during protein metabolism, it is excreted via urine and naturally exists in human skin. It features emollient and diuretic properties.
In biochemical applications, urea is widely utilized for protein denaturation and acts as a gentle solubilizer for insoluble and denatured proteins. It excels at refolding proteins from samples treated with 6M guanidinium chloride, including inclusion bodies. Furthermore, urea can be formulated together with guanidine hydrochloride and DTT to facilitate the refolding of denatured proteins into their natural, biologically active conformation.
