Difference between revisions of "Urea" - New World Encyclopedia
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{| align="right" border="1" cellspacing="0" cellpadding="3" style="margin: 0 0 0 0.5em; background: #FFFFFF; border-collapse: collapse; border-color: #C0C090;" | {| align="right" border="1" cellspacing="0" cellpadding="3" style="margin: 0 0 0 0.5em; background: #FFFFFF; border-collapse: collapse; border-color: #C0C090;" | ||
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| [[Density]] and [[Phase (matter)|phase]] | | [[Density]] and [[Phase (matter)|phase]] | ||
| − | | 1. | + | | 1.33•10<sup>3</sup> kg/m<sup>3</sup> <ref>http://webmineral.com/data/Urea.shtml</ref>, solid |
|- | |- | ||
| [[Soluble|Solubility]] in [[Water (molecule)|water]] | | [[Soluble|Solubility]] in [[Water (molecule)|water]] | ||
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| n.a. | | n.a. | ||
|- | |- | ||
| − | | [[Acid dissociation constant|Acidity]] (p''K''<sub>a</sub>) <!-- omit if not an acid or a base. | + | | [[Acid dissociation constant|Acidity]] (p''K''<sub>a</sub>) <!-- omit if not an acid or a base. If several values, be clear —> |
| 0.18 | | 0.18 | ||
|- | |- | ||
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|- | |- | ||
| [[Critical relative humidity]] | | [[Critical relative humidity]] | ||
| − | | 81% ( | + | | 81% (20 °C)<br/>73% (30 °C) |
|- | |- | ||
| Heat of solution in water | | Heat of solution in water | ||
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|- | |- | ||
| − | ! {{chembox header}} | Hazards <!-- | + | ! {{chembox header}} | Hazards <!-- Summary only- MSDS entry provides more complete information —> |
|- | |- | ||
| [[Material safety data sheet|MSDS]] | | [[Material safety data sheet|MSDS]] | ||
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|- | |- | ||
| Related compounds | | Related compounds | ||
| − | <!-- A miscellaneous heading- use for covalent inorganics; | + | <!-- A miscellaneous heading- use for covalent inorganics; e.g. for PCl<sub>3</sub> you would list PCl<sub>5</sub>, POCl<sub>3</sub>, PF<sub>3</sub>, PBr<sub>3</sub>, NCl<sub>3</sub> and AsCl<sub>3</sub>. |
Please omit if not applicable —> | Please omit if not applicable —> | ||
| ? | | ? | ||
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'''Urea''' is an [[organic compound]] of [[carbon]], [[nitrogen]], [[oxygen]] and [[hydrogen]], with the [[chemical formula|formula]] CON<sub>2</sub>H<sub>4</sub> or (NH<sub>2</sub>)<sub>2</sub>CO or CN<sub>2</sub>H<sub>4</sub>O. | '''Urea''' is an [[organic compound]] of [[carbon]], [[nitrogen]], [[oxygen]] and [[hydrogen]], with the [[chemical formula|formula]] CON<sub>2</sub>H<sub>4</sub> or (NH<sub>2</sub>)<sub>2</sub>CO or CN<sub>2</sub>H<sub>4</sub>O. | ||
| Line 147: | Line 148: | ||
Urea was discovered by [[Hilaire Rouelle]] in 1773. It was the first organic compound to be artificially synthesized from inorganic starting materials, in 1828 by [[Friedrich Wöhler]], who prepared it by the reaction of [[potassium cyanate]] with [[ammonium sulfate]]. Although Wöhler was attempting to prepare ammonium cyanate, by forming urea, he inadvertently disproved [[vitalism]], the theory that the chemicals of living organisms are fundamentally different from inanimate matter, thus starting the discipline of [[organic chemistry]]. | Urea was discovered by [[Hilaire Rouelle]] in 1773. It was the first organic compound to be artificially synthesized from inorganic starting materials, in 1828 by [[Friedrich Wöhler]], who prepared it by the reaction of [[potassium cyanate]] with [[ammonium sulfate]]. Although Wöhler was attempting to prepare ammonium cyanate, by forming urea, he inadvertently disproved [[vitalism]], the theory that the chemicals of living organisms are fundamentally different from inanimate matter, thus starting the discipline of [[organic chemistry]]. | ||
| − | It is found in | + | It is found in [[mammal]]ian and [[amphibian]] urine as well as in some [[fish]]es. [[Bird]]s and [[reptile]]s excrete [[uric acid]], comprising a different form of nitrogen metabolism that requires less water. |
==Physiology== | ==Physiology== | ||
| − | The individual atoms that make up a urea molecule come from [[carbon dioxide]], water, [[aspartate]] and [[ammonia]] in a [[metabolic pathway]] known as the [[urea cycle]], an [[Anabolism|anabolic process]]. | + | The individual atoms that make up a urea molecule come from [[carbon dioxide]], water, [[aspartate]] and [[ammonia]] in a [[metabolic pathway]] known as the [[urea cycle]], an [[Anabolism|anabolic process]]. This expenditure of energy is necessary because ammonia, a common [[metabolism|metabolic]] waste product, is toxic and must be neutralized. Urea production occurs in the [[liver]] and is under the regulatory control of ''N''-acetylglutamate. |
| − | Most [[organism]]s have to deal with the excretion of nitrogen waste originating from [[protein]] and [[amino acid]] [[catabolism]]. In [[marine biology|aquatic]] organisms the ''most common'' form of nitrogen waste is ammonia, while land-dwelling organisms [[adaptation|developed]] ways to convert the toxic ammonia to either urea or [[uric acid]]. Generally, [[bird]]s and [[saurian]] [[reptile]]s excrete uric acid, while the remaining species, including [[mammal]]s, excrete urea. Remarkably, [[tadpole]]s excrete ammonia, and shift to urea production during [[ | + | Most [[organism]]s have to deal with the excretion of nitrogen waste originating from [[protein]] and [[amino acid]] [[catabolism]]. In [[marine biology|aquatic]] organisms the ''most common'' form of nitrogen waste is ammonia, while land-dwelling organisms [[adaptation|developed]] ways to convert the toxic ammonia to either urea or [[uric acid]]. Generally, [[bird]]s and [[saurian]] [[reptile]]s excrete uric acid, while the remaining species, including [[mammal]]s, excrete urea. Remarkably, [[tadpole]]s excrete ammonia, and shift to urea production during [[metamorphosis]]. In veterinary medicine, dalmatian breeds of dogs are different in that they excrete urea in the form of uric acid in the urine rather than in the urea form. This is due to a defect in one of the genes controlling expression of the conversion enzymes in the urea cycle. |
| − | The urea is formed in the livers of mammals in a cyclic pathway, from the break down of [[ammonia]], (a metabolic waste), which was initially named the Krebs-Henseleit cycle after its discoverers, and later became known simply as the [[urea cycle]]. This cycle was partially deduced by [[Krebs]] | + | The urea is formed in the livers of mammals in a cyclic pathway, from the break down of [[ammonia]], (a metabolic waste), which was initially named the Krebs-Henseleit cycle after its discoverers, and later became known simply as the [[urea cycle]]. This cycle was partially deduced by [[Hans Adolf Krebs]] and [[Kurt Henseleit]] in 1932 and was clarified in the 1940s as the roles of [[citrulline]] and [[argininosuccinate]] as intermediates were understood. |
In this cycle, [[amino]] groups donated by [[ammonia]] and L-[[aspartate]] are converted to urea, while L-[[ornithine]], citrulline, L-arginino-succinate, and L-[[arginine]] act as intermediates. | In this cycle, [[amino]] groups donated by [[ammonia]] and L-[[aspartate]] are converted to urea, while L-[[ornithine]], citrulline, L-arginino-succinate, and L-[[arginine]] act as intermediates. | ||
| Line 161: | Line 162: | ||
Despite the generalization above, the pathway has been documented not only in mammals and amphibians, but in many other organisms as well, including birds, [[invertebrate]]s, [[insect]]s, [[plant]]s, [[yeast]], [[fungi]], and even [[microorganism]]s. | Despite the generalization above, the pathway has been documented not only in mammals and amphibians, but in many other organisms as well, including birds, [[invertebrate]]s, [[insect]]s, [[plant]]s, [[yeast]], [[fungi]], and even [[microorganism]]s. | ||
| − | Urea is essentially a waste product, although it is used by the body during times of volume reduction. | + | Urea is essentially a waste product, although it is used by the body during times of volume reduction. In the later portions of the [[kidney]] collecting tubule, urea is reintroduced into the kidney medulla to raise osmolarity. Afterwards, water flowing through the collecting tubule follows back into the body by [[osmosis]]. |
| − | Urea is dissolved in blood (in humans in a concentration of 2.5 | + | Urea is dissolved in blood (in humans in a concentration of 2.5–7.5 mmol/liter) and excreted by the kidney in the [[urine]]. |
In addition, a small amount of urea is excreted (along with [[sodium chloride]] and water) in human [[sweat]]. | In addition, a small amount of urea is excreted (along with [[sodium chloride]] and water) in human [[sweat]]. | ||
| Line 169: | Line 170: | ||
==Production== | ==Production== | ||
| − | Urea is a nitrogen-containing chemical product which is produced on a scale of some 100,000,000 | + | Urea is a nitrogen-containing chemical product which is produced on a scale of some 100,000,000 tons per year worldwide. |
Urea is produced commercially from synthetic [[ammonia]] and [[carbon dioxide]]. Urea can be produced as [[prill]]s, [[granules]], flakes, pellets, crystals and solutions. | Urea is produced commercially from synthetic [[ammonia]] and [[carbon dioxide]]. Urea can be produced as [[prill]]s, [[granules]], flakes, pellets, crystals and solutions. | ||
| − | More than 90 | + | More than 90 percent of world production is destined for use as a [[fertilizer]]. Urea has the highest [[nitrogen]] content of all solid nitrogenous fertilizers in common use (46.4 percent) It therefore has the lowest transportation costs per unit of nitrogen [[nutrient]]. |
Urea is highly soluble in water and is therefore also very suitable for use in fertilizer solutions (in combination with [[ammonium nitrate]]: [[UAN]]), e.g. in 'foliar feed' fertilizers. | Urea is highly soluble in water and is therefore also very suitable for use in fertilizer solutions (in combination with [[ammonium nitrate]]: [[UAN]]), e.g. in 'foliar feed' fertilizers. | ||
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===Commercial production=== | ===Commercial production=== | ||
| − | Urea is produced commercially from two raw materials | + | Urea is produced commercially from two raw materials: [[ammonia]] and [[carbon dioxide]]. Large quantities of carbon dioxide are produced during the manufacture of ammonia from coal or from [[hydrocarbon]]s such as [[natural gas]] and [[petroleum]] derived raw materials. This allows direct synthesis of urea from these raw materials. |
The production of urea from ammonia and carbon dioxide takes place in an equilibrium reaction, with incomplete conversion of the reactants. The various urea processes are characterized by the conditions under which urea formation takes place and the way in which unconverted reactants are further processed. | The production of urea from ammonia and carbon dioxide takes place in an equilibrium reaction, with incomplete conversion of the reactants. The various urea processes are characterized by the conditions under which urea formation takes place and the way in which unconverted reactants are further processed. | ||
| Line 188: | Line 189: | ||
Two principal reactions take place in the formation of urea from [[ammonia]] and [[carbon dioxide]]. The first reaction is exothermic: | Two principal reactions take place in the formation of urea from [[ammonia]] and [[carbon dioxide]]. The first reaction is exothermic: | ||
| − | :2NH<sub>3</sub> + CO<sub>2</sub> → H<sub>2</sub>N-COONH<sub>4</sub> ([[ammonium carbamate]]) | + | :2NH<sub>3</sub> + CO<sub>2</sub> → H<sub>2</sub>N-COONH<sub>4</sub> ([[ammonium carbamate]]) <br /> |
While the second reaction is endothermic: | While the second reaction is endothermic: | ||
:H<sub>2</sub>N-COONH<sub>4</sub> → (NH<sub>2</sub>)<sub>2</sub>CO + H<sub>2</sub>O | :H<sub>2</sub>N-COONH<sub>4</sub> → (NH<sub>2</sub>)<sub>2</sub>CO + H<sub>2</sub>O | ||
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*As a component of [[fertilizer]] and [[animal feed]], providing a relatively cheap source of [[Nitrogen fixation|fixed nitrogen]] to promote growth. | *As a component of [[fertilizer]] and [[animal feed]], providing a relatively cheap source of [[Nitrogen fixation|fixed nitrogen]] to promote growth. | ||
*As an alternative to rock salt in the deicing of roadways and runways. It does not promote metal corrosion to the extent that salt does. | *As an alternative to rock salt in the deicing of roadways and runways. It does not promote metal corrosion to the extent that salt does. | ||
| − | *As an additive ingredient in [[cigarette]]s, designed to enhance [[ | + | *As an additive ingredient in [[cigarette]]s, designed to enhance [[flavor]]. |
| − | *Sometimes used as a browning agent in factory-produced [[ | + | *Sometimes used as a browning agent in factory-produced [[pretzel]]s. |
*As an ingredient in some hair conditioners, facial cleansers, bath oils and lotions. | *As an ingredient in some hair conditioners, facial cleansers, bath oils and lotions. | ||
*It is also used as a [[reactant]] in some ready-to-use cold compresses for first-aid use, due to the [[endothermic]] reaction it creates when mixed with [[water]]. | *It is also used as a [[reactant]] in some ready-to-use cold compresses for first-aid use, due to the [[endothermic]] reaction it creates when mixed with [[water]]. | ||
| − | *Active ingredient for diesel engine exhaust treatment | + | *Active ingredient for diesel-engine exhaust treatment AdBlue and some other SCR systems. |
*Used, along with salts, as a [[cloud seeding]] agent to expedite the condensation of water in clouds, producing precipitation. | *Used, along with salts, as a [[cloud seeding]] agent to expedite the condensation of water in clouds, producing precipitation. | ||
*The ability of urea to form [[clathrates]] (also called host-guest complexes, inclusion compounds, and adducts) was used in the past to separate paraffins. | *The ability of urea to form [[clathrates]] (also called host-guest complexes, inclusion compounds, and adducts) was used in the past to separate paraffins. | ||
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===Laboratory use=== | ===Laboratory use=== | ||
| − | * Urea is a powerful [[protein]] [[denaturation (biochemistry)|denaturant]]. | + | * Urea is a powerful [[protein]] [[denaturation (biochemistry)|denaturant]]. This property can be exploited to increase the solubility of some proteins. For this application it is used in concentrations up to 10 [[Molar volume|M]]. |
* Urea is used to effectively disrupt the noncovalent bonds in proteins. | * Urea is used to effectively disrupt the noncovalent bonds in proteins. | ||
* Urea is an ingredient in the synthesis of [[urea nitrate]]. | * Urea is an ingredient in the synthesis of [[urea nitrate]]. | ||
| Line 222: | Line 223: | ||
;Drug use | ;Drug use | ||
| − | Urea is used in topical [[Dermatology|dermatological]] products to promote [[rehydration]] of the [[skin]]. | + | Urea is used in topical [[Dermatology|dermatological]] products to promote [[rehydration]] of the [[skin]]. If covered by an [[occlusive dressing]], 40 percent urea preparations may also be used for nonsurgical [[debridement]] of [[Nail (anatomy)|nails]]. |
;Clinical diagnosis | ;Clinical diagnosis | ||
| Line 228: | Line 229: | ||
;Other diagnostic use | ;Other diagnostic use | ||
| − | Isotopically-labeled urea ([[carbon-14|carbon 14]] - radioactive, or [[Carbon-13|carbon 13]] - stable isotope) is used in the [[Urea breath test]], which is used to detect the presence of ''[[Helicobacter pylori]]'' (''H. pylori'', a bacterium) in the stomach and duodenum of humans. | + | Isotopically-labeled urea ([[carbon-14|carbon 14]]-radioactive, or [[Carbon-13|carbon 13]]-stable isotope) is used in the [[Urea breath test]], which is used to detect the presence of ''[[Helicobacter pylori]]'' (''H. pylori'', a bacterium) in the stomach and duodenum of humans. The test detects the characteristic enzyme urease, produced by ''H. pylori'', by a reaction that produces ammonia from urea. This increases the pH (reduces acidity) of the stomach environment around the bacteria. |
| − | Similar bacteria species to ''H. pylori'' can be identified by the same test in animals (apes, dogs, | + | Similar bacteria species to ''H. pylori'' can be identified by the same test in animals (apes, dogs and cats, including big cats). |
===Textile use=== | ===Textile use=== | ||
| Line 248: | Line 249: | ||
== Notes == | == Notes == | ||
<references/> | <references/> | ||
| − | |||
| − | |||
| − | |||
==External links== | ==External links== | ||
| + | All links retrieved June 15, 2007. | ||
* [http://www.jtbaker.com/msds/englishhtml/U4725.htm MSDS sheet on urea] | * [http://www.jtbaker.com/msds/englishhtml/U4725.htm MSDS sheet on urea] | ||
* [http://www.pburch.net/dyeing/FAQ/urea.shtml Use of urea in hand dyeing] | * [http://www.pburch.net/dyeing/FAQ/urea.shtml Use of urea in hand dyeing] | ||
* [http://www.globalcheminfo.com/chemicals/details/41837 Urea: synonymes, CAS, formula] | * [http://www.globalcheminfo.com/chemicals/details/41837 Urea: synonymes, CAS, formula] | ||
| − | * [http://www.u3kenergy.com U3K Energy | + | * [http://www.u3kenergy.com U3K Energy] – Patented technology for use of urea as fuel (not SCR additive) for internal combustion engines and fuel cells] |
[[Category:Physical sciences]] | [[Category:Physical sciences]] | ||
Revision as of 20:46, 15 June 2007
| Urea | |
|---|---|
 
| |
| General | |
| Systematic name | Diaminomethanal |
| Other names | carbamide |
| Molecular formula | (NH2)2CO |
| SMILES | NC(=O)N |
| Molar mass | 60.07 g/mol |
| Appearance | white odourless solid |
| CAS number | [57-13-6] |
| Properties | |
| Density and phase | 1.33•103 kg/m3 [1], solid |
| Solubility in water | 108 g/100 ml (20 °C) 167 g/100 ml (40 °C) 251 g/100 ml (60 °C) 400 g/100 ml (80 °C) 733 g/100 ml (100 °C) |
| Melting point | 132.7 °C (406 K) decomposes |
| Boiling point | n.a. |
| Acidity (pKa) | 0.18 |
| Basicity (pKb) | 13.82 |
| Chiral rotation [α]D | Not chiral |
| Viscosity | ? cP at ? °C |
| Critical relative humidity | 81% (20 °C) 73% (30 °C) |
| Heat of solution in water | -57,8 cal/g (endothermic) |
| Nitrogen content | 46,6 %N |
| Structure | |
| Molecular shape | ? |
| Coordination geometry | trigonal planar |
| Crystal structure | tetragonal |
| Dipole moment | 4.56 p/D |
| Hazards | |
| MSDS | J.T. Baker |
| Main hazards | Toxic |
| Flash point | ? °C |
| R/S statement | R: ? S: ? |
| RTECS number | ? |
| NFPA 704 |
0
1
0
|
| Supplementary data page | |
| Structure & properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | ? |
| Other cations | ? |
| Related ? | biuret triuret thiourea |
| Related compounds | ? |
| Except where noted otherwise, data are given for materials in their standard state (at 26°C, 100 kPa) Infobox disclaimer and references | |
Urea is an organic compound of carbon, nitrogen, oxygen and hydrogen, with the formula CON2H4 or (NH2)2CO or CN2H4O.
Urea is also known as carbamide, especially in the recommended International Nonproprietary Names (rINN) in use in Europe. For example, the medicinal compound hydroxyurea (old British Approved Name) is now hydroxycarbamide. Other names include carbamide resin, isourea, carbonyl diamide, and carbonyldiamine.
It was the first organic compound to be artificially synthesized from inorganic starting materials, thus dispelling the concept of vitalism.
Discovery
Urea was discovered by Hilaire Rouelle in 1773. It was the first organic compound to be artificially synthesized from inorganic starting materials, in 1828 by Friedrich Wöhler, who prepared it by the reaction of potassium cyanate with ammonium sulfate. Although Wöhler was attempting to prepare ammonium cyanate, by forming urea, he inadvertently disproved vitalism, the theory that the chemicals of living organisms are fundamentally different from inanimate matter, thus starting the discipline of organic chemistry.
It is found in mammalian and amphibian urine as well as in some fishes. Birds and reptiles excrete uric acid, comprising a different form of nitrogen metabolism that requires less water.
Physiology
The individual atoms that make up a urea molecule come from carbon dioxide, water, aspartate and ammonia in a metabolic pathway known as the urea cycle, an anabolic process. This expenditure of energy is necessary because ammonia, a common metabolic waste product, is toxic and must be neutralized. Urea production occurs in the liver and is under the regulatory control of N-acetylglutamate.
Most organisms have to deal with the excretion of nitrogen waste originating from protein and amino acid catabolism. In aquatic organisms the most common form of nitrogen waste is ammonia, while land-dwelling organisms developed ways to convert the toxic ammonia to either urea or uric acid. Generally, birds and saurian reptiles excrete uric acid, while the remaining species, including mammals, excrete urea. Remarkably, tadpoles excrete ammonia, and shift to urea production during metamorphosis. In veterinary medicine, dalmatian breeds of dogs are different in that they excrete urea in the form of uric acid in the urine rather than in the urea form. This is due to a defect in one of the genes controlling expression of the conversion enzymes in the urea cycle.
The urea is formed in the livers of mammals in a cyclic pathway, from the break down of ammonia, (a metabolic waste), which was initially named the Krebs-Henseleit cycle after its discoverers, and later became known simply as the urea cycle. This cycle was partially deduced by Hans Adolf Krebs and Kurt Henseleit in 1932 and was clarified in the 1940s as the roles of citrulline and argininosuccinate as intermediates were understood.
In this cycle, amino groups donated by ammonia and L-aspartate are converted to urea, while L-ornithine, citrulline, L-arginino-succinate, and L-arginine act as intermediates.
Despite the generalization above, the pathway has been documented not only in mammals and amphibians, but in many other organisms as well, including birds, invertebrates, insects, plants, yeast, fungi, and even microorganisms.
Urea is essentially a waste product, although it is used by the body during times of volume reduction. In the later portions of the kidney collecting tubule, urea is reintroduced into the kidney medulla to raise osmolarity. Afterwards, water flowing through the collecting tubule follows back into the body by osmosis.
Urea is dissolved in blood (in humans in a concentration of 2.5–7.5 mmol/liter) and excreted by the kidney in the urine.
In addition, a small amount of urea is excreted (along with sodium chloride and water) in human sweat.
Production
Urea is a nitrogen-containing chemical product which is produced on a scale of some 100,000,000 tons per year worldwide.
Urea is produced commercially from synthetic ammonia and carbon dioxide. Urea can be produced as prills, granules, flakes, pellets, crystals and solutions.
More than 90 percent of world production is destined for use as a fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use (46.4 percent) It therefore has the lowest transportation costs per unit of nitrogen nutrient.
Urea is highly soluble in water and is therefore also very suitable for use in fertilizer solutions (in combination with ammonium nitrate: UAN), e.g. in 'foliar feed' fertilizers.
Solid urea is marketed as prills or granules. The advantage of prills is that in general they can be produced more cheaply than granules which, because of their narrower particle size distribution have an advantage over prills if applied mechanically to the soil. Properties such as impact strength, crushing strength and free-flowing behaviour are particularly important in product handling, storage and bulk transportation.
Commercial production
Urea is produced commercially from two raw materials: ammonia and carbon dioxide. Large quantities of carbon dioxide are produced during the manufacture of ammonia from coal or from hydrocarbons such as natural gas and petroleum derived raw materials. This allows direct synthesis of urea from these raw materials.
The production of urea from ammonia and carbon dioxide takes place in an equilibrium reaction, with incomplete conversion of the reactants. The various urea processes are characterized by the conditions under which urea formation takes place and the way in which unconverted reactants are further processed.
Unconverted reactants can be used for the manufacture of other products, for example ammonium nitrate or sulphate, or they can be recycled for complete conversion to urea in a total-recycle process.
Two principal reactions take place in the formation of urea from ammonia and carbon dioxide. The first reaction is exothermic:
- 2NH3 + CO2 → H2N-COONH4 (ammonium carbamate)
While the second reaction is endothermic:
- H2N-COONH4 → (NH2)2CO + H2O
Both reactions combined are exothermic.
Uses
Commercial uses
- As a raw material for the manufacture of plastics specifically, urea-formaldehyde resin.
- As a raw material for the manufacture of various glues (urea-formaldehyde or urea-melamine-formaldehyde). The latter is waterproof and is used for marine plywood.
- As a component of fertilizer and animal feed, providing a relatively cheap source of fixed nitrogen to promote growth.
- As an alternative to rock salt in the deicing of roadways and runways. It does not promote metal corrosion to the extent that salt does.
- As an additive ingredient in cigarettes, designed to enhance flavor.
- Sometimes used as a browning agent in factory-produced pretzels.
- As an ingredient in some hair conditioners, facial cleansers, bath oils and lotions.
- It is also used as a reactant in some ready-to-use cold compresses for first-aid use, due to the endothermic reaction it creates when mixed with water.
- Active ingredient for diesel-engine exhaust treatment AdBlue and some other SCR systems.
- Used, along with salts, as a cloud seeding agent to expedite the condensation of water in clouds, producing precipitation.
- The ability of urea to form clathrates (also called host-guest complexes, inclusion compounds, and adducts) was used in the past to separate paraffins.
- As a flame-proofing agent.
- As a clean burning fuel for motor vehicles and stationary engines.
- As a NOx-reducing reactant in combustion exhaust streams, especially diesel.
- As an ingredient in many tooth whitening products.
- Used in coal fired power plants to reduce NO emissions.
Laboratory use
- Urea is a powerful protein denaturant. This property can be exploited to increase the solubility of some proteins. For this application it is used in concentrations up to 10 M.
- Urea is used to effectively disrupt the noncovalent bonds in proteins.
- Urea is an ingredient in the synthesis of urea nitrate.
Medical uses
- Drug use
Urea is used in topical dermatological products to promote rehydration of the skin. If covered by an occlusive dressing, 40 percent urea preparations may also be used for nonsurgical debridement of nails.
- Clinical diagnosis
See blood urea nitrogen ("BUN") for a commonly performed urea test, and marker of renal function.
- Other diagnostic use
Isotopically-labeled urea (carbon 14-radioactive, or carbon 13-stable isotope) is used in the Urea breath test, which is used to detect the presence of Helicobacter pylori (H. pylori, a bacterium) in the stomach and duodenum of humans. The test detects the characteristic enzyme urease, produced by H. pylori, by a reaction that produces ammonia from urea. This increases the pH (reduces acidity) of the stomach environment around the bacteria.
Similar bacteria species to H. pylori can be identified by the same test in animals (apes, dogs and cats, including big cats).
Textile use
Urea in textile laboratories are frequently used both in dyeing and printing as an important auxiliary which provides solubility to the bath and retains some moisture which is required for the dyeing or printing process.
Ureas
Ureas or carbamides are a class of chemical compounds sharing the same functional group RR'N-CO-NRR' based on a carbonyl group flanked by two organic amine residues. They can be accessed in the laboratory by reaction of phosgene with primary or secondary amines. Example of ureas are the compounds carbamide peroxide, allantoin and Hydantoin. Ureas are closely related to biurets and structurally related to amides, carbamates, diimides, carbodiimides and thiocarbamides.
See also
Notes
External links
All links retrieved June 15, 2007.
- MSDS sheet on urea
- Use of urea in hand dyeing
- Urea: synonymes, CAS, formula
- U3K Energy – Patented technology for use of urea as fuel (not SCR additive) for internal combustion engines and fuel cells]
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