Urea

Urea is one of the carboxylic acid amides and is the diamide of carbonic acid. The compound's compact molecules consist of a single carbon atom, which has a double bond to an oxygen atom, and two amino groups. This structure of the substance is expressed using the alternative name diaminomethanone.

There are tight hydrogen bonds between the hydrogen atoms of the amino group and the oxygen atom, while the bonds between the nitrogen atoms and the carbon center almost have the character of a double bond. As a result, the intramolecular forces of attraction are strong, therefore the crystals only melt at high temperatures.

Urea is a colorless to yellowish-brown solid that is in crystalline form. The compound has only a very faint odor reminiscent of ammonia. The substance is very soluble in water and polar organic solvents such as glycerine, ethanol and methanol. In contrast, urea is practically insoluble in chloroform, diethyl ether and benzene.

In aqueous solution, the substance has a pH of 9. When heated, it forms ammonium salts and carbon dioxide together with acids. When heated together with bases, ammonia and carbonates are formed. Urea decomposes when it reaches its melting point at 133°C. Harmful amounts of nitrogen oxides can be released in the process.

When stored dry and airtight, urea is a chemically very stable substance, which, however, can react dangerously with a large number of compounds such as fluorine, hydrogen peroxide, alkalis, alkali chromates, alkali nitrates, alkali chlorites, perchlorates and strong oxidizing agents. There is a risk of explosion on contact with various nitrates, nitrites and certain chlorine-containing compounds. The substance should be stored in stainless steel and glass vessels.

In its pure form, urea is not flammable. However, there is a risk of a dust explosion if large numbers of fine particles of the compound are whirled up and the resulting dust-air mixture comes into contact with an ignition source. When handling open containers of the substance, it is therefore important to ensure that there is sufficient distance to open flames, sparks, electrical discharges and strongly heated surfaces.

Toxicologically, urea is largely harmless and does not represent a dangerous compound according to the GHS classification. However, when the substance is processed, contact with the skin or eyes can cause irritation and redness. Repeated exposure to the compound can lead to the development of dermatitis. Affected parts of the body should therefore be cleaned thoroughly with soap and water. The eye should be rinsed thoroughly with water after contact. An ophthalmological treatment is recommended.

Inhalation of substance dust can cause irritation of the respiratory tract. Urea is an endogenous metabolite and can be easily broken down by the body if small amounts are absorbed. However, if larger amounts of the substance are swallowed, a medical examination must be arranged.

Due to possible damage to aquatic organisms, urea is considered a slightly water-polluting substance that should not enter the ground, water bodies or waste water. In the environment, the compound contributes to the growth of toxic algae. The local authorities must be informed if large quantities of the substance escape. Urea is not subject to any special transport regulations..