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Urea
Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula CO(NH2)2. This amide has two amino groups (−NH2) joined by a carbonyl functional group (−C(=O)−). It is thus the simplest amide of carbamic acid.
Urea serves an important role in the cellular metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals. Urea is Neo-Latin, from French urée, from Ancient Greek οὖρον (oûron) 'urine', itself from Proto-Indo-European *h₂worsom.
It is a colorless, odorless solid, highly soluble in water, and practically non-toxic (LD50 is 15 g/kg for rats). Dissolved in water, it is neither acidic nor alkaline. The body uses it in many processes, most notably nitrogen excretion. The liver forms it by combining two ammonia molecules (NH3) with a carbon dioxide (CO2) molecule in the urea cycle. Urea is widely used in fertilizers as a source of nitrogen (N) and is an important raw material for the chemical industry.
In 1828, Friedrich Wöhler discovered that urea can be produced from inorganic starting materials, an important conceptual milestone in chemistry. This showed for the first time that a substance previously known only as a byproduct of life could be synthesized in the laboratory from non-biological starting materials, thereby contradicting the widely held doctrine of vitalism, which stated that organic compounds could only be derived from living organisms.
The structure of the molecule of urea is O=C(−NH2)2. The urea molecule is planar when in a solid crystal because of sp2 hybridization of the N orbitals. It is non-planar with C2 symmetry when in the gas phase or in aqueous solution, with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°. In solid urea, the oxygen center is engaged in two N–H–O hydrogen bonds. The resulting hydrogen-bond network is probably established at the cost of efficient molecular packing: The structure is quite open, the ribbons forming tunnels with square cross-section. The carbon in urea is described as sp2 hybridized, the C-N bonds have significant double bond character, and the carbonyl oxygen is relatively basic. Urea's high aqueous solubility reflects its ability to engage in extensive hydrogen bonding with water.
By virtue of its tendency to form porous frameworks, urea has the ability to trap many organic compounds. In these so-called clathrates, the organic "guest" molecules are held in channels formed by interpenetrating helices composed of hydrogen-bonded urea molecules. In this way, urea-clathrates have been well investigated for separations.
Urea is a weak base, with a pKb of 13.9. When combined with strong acids, it undergoes protonation at oxygen to form uronium salts. It is also a Lewis base, forming metal complexes of the type [M(urea)6]n+.
Urea reacts with malonic esters to make barbituric acids.
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Urea
Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula CO(NH2)2. This amide has two amino groups (−NH2) joined by a carbonyl functional group (−C(=O)−). It is thus the simplest amide of carbamic acid.
Urea serves an important role in the cellular metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals. Urea is Neo-Latin, from French urée, from Ancient Greek οὖρον (oûron) 'urine', itself from Proto-Indo-European *h₂worsom.
It is a colorless, odorless solid, highly soluble in water, and practically non-toxic (LD50 is 15 g/kg for rats). Dissolved in water, it is neither acidic nor alkaline. The body uses it in many processes, most notably nitrogen excretion. The liver forms it by combining two ammonia molecules (NH3) with a carbon dioxide (CO2) molecule in the urea cycle. Urea is widely used in fertilizers as a source of nitrogen (N) and is an important raw material for the chemical industry.
In 1828, Friedrich Wöhler discovered that urea can be produced from inorganic starting materials, an important conceptual milestone in chemistry. This showed for the first time that a substance previously known only as a byproduct of life could be synthesized in the laboratory from non-biological starting materials, thereby contradicting the widely held doctrine of vitalism, which stated that organic compounds could only be derived from living organisms.
The structure of the molecule of urea is O=C(−NH2)2. The urea molecule is planar when in a solid crystal because of sp2 hybridization of the N orbitals. It is non-planar with C2 symmetry when in the gas phase or in aqueous solution, with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°. In solid urea, the oxygen center is engaged in two N–H–O hydrogen bonds. The resulting hydrogen-bond network is probably established at the cost of efficient molecular packing: The structure is quite open, the ribbons forming tunnels with square cross-section. The carbon in urea is described as sp2 hybridized, the C-N bonds have significant double bond character, and the carbonyl oxygen is relatively basic. Urea's high aqueous solubility reflects its ability to engage in extensive hydrogen bonding with water.
By virtue of its tendency to form porous frameworks, urea has the ability to trap many organic compounds. In these so-called clathrates, the organic "guest" molecules are held in channels formed by interpenetrating helices composed of hydrogen-bonded urea molecules. In this way, urea-clathrates have been well investigated for separations.
Urea is a weak base, with a pKb of 13.9. When combined with strong acids, it undergoes protonation at oxygen to form uronium salts. It is also a Lewis base, forming metal complexes of the type [M(urea)6]n+.
Urea reacts with malonic esters to make barbituric acids.