Misplaced Pages

#994005

57-638: The parent compound can be prepared by heating urea at 150 °C for ~6 hours until it gets slightly cloudy, then recrystallizing from water . After that, it can be recrystallized repeatedly from 2% sodium hydroxide solution and water to finally get base-free crystalline needles of the monohydrate which are free of cyanuric acid . While heating, a lot of ammonia is expelled: Under related conditions, pyrolysis of urea affords triuret O=C(−N(H)−C(=O)−NH 2 ) 2 . In general, organic biurets (those with alkyl or aryl groups in place of one or more H atoms) are prepared by trimerization of isocyanates . For example,

114-426: A carbon dioxide ( CO 2 ) 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, which was an important conceptual milestone in chemistry. This showed for the first time that a substance previously known only as

171-488: A class of chemical compounds that share the same functional group, a carbonyl group attached to two organic amine residues: R R N−C(=O)−NR R , where R , R , R and R groups are hydrogen (–H), organyl or other groups. Examples include carbamide peroxide , allantoin , and hydantoin . Ureas are closely related to biurets and related in structure to amides , carbamates , carbodiimides , and thiocarbamides . More than 90% of world industrial production of urea

228-410: A byproduct of life could be synthesized in the laboratory without biological starting materials, thereby contradicting the widely held doctrine of vitalism , which stated that only living organisms could produce the chemicals of life. The structure of the molecule of urea is O=C(−NH 2 ) 2 . The urea molecule is planar when in a solid crystal because of sp hybridization of the N orbitals. It

285-561: A lack of raw materials as a reason for their supply chain issues. Forecasting for 2023, 50% of respondents expect a reduced availability of raw materials in the US to drive supply chain disruptions. Raw materials markets are affected by consumer behavior, supply chain uncertainty, manufacturing disruptions, and regulations, amongst other factors. This results in volatile raw materials markets that are difficult to optimize and manage. Companies can struggle when faced with raw material volatility due to

342-459: A lack of understanding of market demands, poor or no visibility into the indirect supply chain, and the time lag of raw materials price changes. Volatility in the raw materials markets can also be driven by natural disasters and geopolitcal conflict. The COVID-19 pandemic disrupted the steel industry, and once demand rebounded, prices increased 250% in the US . The Russian invasion of Ukraine caused

399-412: A muscle loss of 0.67 gram. In aquatic organisms the most common form of nitrogen waste is ammonia, whereas land-dwelling organisms convert the toxic ammonia to either urea or uric acid . Urea is found in the urine of mammals and amphibians , as well as some fish. Birds and saurian reptiles have a different form of nitrogen metabolism that requires less water, and leads to nitrogen excretion in

456-541: A range of condensation products , including cyanuric acid (CNOH) 3 , guanidine HNC(NH 2 ) 2 , and melamine . In aqueous solution, urea slowly equilibrates with ammonium cyanate. This elimination reaction cogenerates isocyanic acid , which can carbamylate proteins, in particular the N-terminal amino group, the side chain amino of lysine , and to a lesser extent the side chains of arginine and cysteine . Each carbamylation event adds 43 daltons to

513-456: A reaction that produces ammonia from urea. This increases the pH (reduces the acidity) of the stomach environment around the bacteria. Similar bacteria species to H. pylori can be identified by the same test in animals such as apes , dogs , and cats (including big cats ). Amino acids from ingested food (or produced from catabolism of muscle protein) that are used for the synthesis of proteins and other biological substances can be oxidized by

570-565: A reaction with nitric acid to make urea nitrate , a high explosive that is used industrially and as part of some improvised explosive devices . Urea is used in Selective Non-Catalytic Reduction (SNCR) and Selective Catalytic Reduction (SCR) reactions to reduce the NO x pollutants in exhaust gases from combustion from diesel , dual fuel, and lean-burn natural gas engines. The BlueTec system, for example, injects

627-410: A solid highly soluble in water (545 g/L at 25 °C), urea is much easier and safer to handle and store than the more irritant , caustic and hazardous ammonia ( NH 3 ), so it is the reactant of choice. Trucks and cars using these catalytic converters need to carry a supply of diesel exhaust fluid , also sold as AdBlue , a solution of urea in water. Urea in concentrations up to 10  M

SECTION 10

#1732868827995

684-406: A stronger odor than fresh urine. The cycling of and excretion of urea by the kidneys is a vital part of mammalian metabolism. Besides its role as carrier of waste nitrogen, urea also plays a role in the countercurrent exchange system of the nephrons , that allows for reabsorption of water and critical ions from the excreted urine . Urea is reabsorbed in the inner medullary collecting ducts of

741-453: A usable state. Metallic ores are first processed through a combination of crushing, roasting, magnetic separation, flotation, and leaching to make them suitable for use in a foundry . Foundries then smelt the ore into usable metal that may be alloyed with other materials to improve certain properties. One metallic raw material that is commonly found across the world is iron , and combined with nickel , this material makes up over 35% of

798-464: A water-based urea solution into the exhaust system. Ammonia ( NH 3 ) produced by the hydrolysis of urea reacts with nitrogen oxides ( NO x ) and is converted into nitrogen gas ( N 2 ) and water within the catalytic converter. The conversion of noxious NO x to innocuous N 2 is described by the following simplified global equation: When urea is used, a pre-reaction (hydrolysis) occurs to first convert it to ammonia: Being

855-449: Is a common byproduct of the metabolism of nitrogenous compounds. Ammonia is smaller, more volatile, and more mobile than urea. If allowed to accumulate, ammonia would raise the pH in cells to toxic levels. Therefore, many organisms convert ammonia to urea, even though this synthesis has a net energy cost. Being practically neutral and highly soluble in water, urea is a safe vehicle for the body to transport and excrete excess nitrogen. Urea

912-415: Is a diamide of carbonic acid ), is an organic compound with chemical formula CO(NH 2 ) 2 . This amide has two amino groups (– NH 2 ) 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

969-813: Is a powerful protein denaturant as it disrupts the noncovalent bonds in the proteins. This property can be exploited to increase the solubility of some proteins. A mixture of urea and choline chloride is used as a deep eutectic solvent (DES), a substance similar to ionic liquid . When used in a deep eutectic solvent, urea gradually denatures the proteins that are solubilized. Urea in concentrations up to 8 M can be used to make fixed brain tissue transparent to visible light while still preserving fluorescent signals from labeled cells. This allows for much deeper imaging of neuronal processes than previously obtainable using conventional one photon or two photon confocal microscopes. Urea-containing creams are used as topical dermatological products to promote rehydration of

1026-694: Is a recommended preparation procedure. However, cyanate will build back up to significant levels within a few days. Alternatively, adding 25–50 mM ammonium chloride to a concentrated urea solution decreases formation of cyanate because of the common ion effect . Urea is readily quantified by a number of different methods, such as the diacetyl monoxime colorimetric method, and the Berthelot reaction (after initial conversion of urea to ammonia via urease). These methods are amenable to high throughput instrumentation, such as automated flow injection analyzers and 96-well micro-plate spectrophotometers. Ureas describes

1083-400: Is also used as a non-protein nitrogen source in ruminant feed, where it is converted into protein by gut microorganisms. It is less favored than urea, due to its higher cost and lower digestibility but the latter characteristic also slows down its digestion and so decreases the risk of ammonia toxicity. The biuret test is a chemical test for proteins and polypeptides . It is based on

1140-414: Is controlled by the antidiuretic hormone , to create hyperosmotic urine — i.e., urine with a higher concentration of dissolved substances than the blood plasma . This mechanism is important to prevent the loss of water, maintain blood pressure , and maintain a suitable concentration of sodium ions in the blood plasma. The equivalent nitrogen content (in grams ) of urea (in mmol ) can be estimated by

1197-409: Is destined for use as a nitrogen-release fertilizer . Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has a low transportation cost per unit of nitrogen nutrient . The most common impurity of synthetic urea is biuret , which impairs plant growth. Urea breaks down in the soil to give ammonium ions ( NH + 4 ). The ammonium is taken up by

SECTION 20

#1732868827995

1254-657: Is no longer in widespread use. The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. It is used as a marker of renal function , though it is inferior to other markers such as creatinine because blood urea levels are influenced by other factors such as diet, dehydration, and liver function. Urea has also been studied as an excipient in Drug-coated Balloon (DCB) coating formulation to enhance local drug delivery to stenotic blood vessels. Urea, when used as an excipient in small doses (~3 μg/mm ) to coat DCB surface

1311-413: Is non-planar with C 2 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

1368-502: Is often attributed to the French chemist Hilaire Rouelle as well as William Cruickshank . Boerhaave used the following steps to isolate urea: In 1828, the German chemist Friedrich Wöhler obtained urea artificially by treating silver cyanate with ammonium chloride . This was the first time an organic compound was artificially synthesized from inorganic starting materials, without

1425-510: Is quite open, the ribbons forming tunnels with square cross-section. The carbon in urea is described as sp 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 ,

1482-420: Is synthesized in the body of many organisms as part of the urea cycle , either from the oxidation of amino acids or from ammonia . In this cycle, amino groups donated by ammonia and L - aspartate are converted to urea, while L - ornithine , citrulline , L - argininosuccinate , and L - arginine act as intermediates. Urea production occurs in the liver and is regulated by N -acetylglutamate . Urea

1539-437: Is then dissolved into the blood (in the reference range of 2.5 to 6.7 mmol/L) and further transported and excreted by the kidney as a component of urine . In addition, a small amount of urea is excreted (along with sodium chloride and water) in sweat . In water, the amine groups undergo slow displacement by water molecules, producing ammonia, ammonium ions , and bicarbonate ions . For this reason, old, stale urine has

1596-405: Is then evaporated and anhydrous alcohol added to extract the urea. This solution is drained off and evaporated, leaving pure urea. Ureas in the more general sense can be accessed in the laboratory by reaction of phosgene with primary or secondary amines : Raw material A raw material , also known as a feedstock , unprocessed material , or primary commodity , is a basic material that

1653-618: Is used to produce goods , finished goods , energy, or intermediate materials that are feedstock for future finished products. As feedstock, the term connotes these materials are bottleneck assets and are required to produce other products. The term raw material denotes materials in unprocessed or minimally processed states such as raw latex , crude oil , cotton , coal , raw biomass , iron ore , plastic , air , logs , and water . The term secondary raw material denotes waste material which has been recycled and injected back into use as productive material. Supply chains typically begin with

1710-593: The biuret reagent , a blue solution that turns violet upon contact with proteins, or any substance with peptide bonds . The test and reagent do not actually contain biuret; they are so named because both biuret and proteins have the same response to the test. Biuret was first prepared and studied by Gustav Heinrich Wiedemann (1826–1899) for his doctoral dissertation, which was submitted in 1847. His findings were reported in several articles. Urea   50 g/L ethanol   ~4 g/L acetonitrile Urea , also called carbamide (because it

1767-432: The skin . Urea 40% is indicated for psoriasis , xerosis , onychomycosis , ichthyosis , eczema , keratosis , keratoderma , corns, and calluses . If covered by an occlusive dressing , 40% urea preparations may also be used for nonsurgical debridement of nails . Urea 40% "dissolves the intercellular matrix" of the nail plate. Only diseased or dystrophic nails are removed, as there is no effect on healthy portions of

Biuret - Misplaced Pages Continue

1824-532: 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 ( LD 50 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 ( NH 3 ) with

1881-613: The water to create very stable and hard materials. Without the presence of clay on the riverbanks of the Tigris and Euphrates in the Fertile Crescent, such kilns would have been impossible for people in the region to have produced. Using these kilns, the process of metallurgy was possible once the Bronze and Iron Ages came upon the people that lived there. Many raw metallic materials used in industrial purposes must first be processed into

1938-569: The acquisition or extraction of raw materials. For example, the European Commission notes that food supply chains commence in the agricultural phase of food production. A 2022 report on changes affecting international trade noted that improving sourcing of raw materials has become one of the main objectives of companies reconfiguring their supply chains. In a 2022 survey conducted by SAP , wherein 400 US-based leaders in logistics and supply chain were interviewed, 44% of respondents cited

1995-444: The advent of dialysis . It is the classical pre-dialysis era description of crystallized urea deposits over the skin of patients with prolonged kidney failure and severe uremia. Urea was first noticed by Herman Boerhaave in the early 18th century from evaporates of urine. In 1773, Hilaire Rouelle obtained crystals containing urea from human urine by evaporating it and treating it with alcohol in successive filtrations. This method

2052-528: The body as an alternative source of energy, yielding urea and carbon dioxide . The oxidation pathway starts with the removal of the amino group by a transaminase ; the amino group is then fed into the urea cycle . The first step in the conversion of amino acids into metabolic waste in the liver is removal of the alpha-amino nitrogen, which produces ammonia . Because ammonia is toxic, it is excreted immediately by fish, converted into uric acid by birds, and converted into urea by mammals. Ammonia ( NH 3 )

2109-428: The chemical composition of the pure substance. In the evolved procedure, urea was precipitated as urea nitrate by adding strong nitric acid to urine. To purify the resulting crystals, they were dissolved in boiling water with charcoal and filtered. After cooling, pure crystals of urea nitrate form. To reconstitute the urea from the nitrate, the crystals are dissolved in warm water, and barium carbonate added. The water

2166-407: The conversion factor 0.028 g/mmol. Furthermore, 1 gram of nitrogen is roughly equivalent to 6.25 grams of protein , and 1 gram of protein is roughly equivalent to 5 grams of muscle tissue. In situations such as muscle wasting , 1 mmol of excessive urea in the urine (as measured by urine volume in litres multiplied by urea concentration in mmol/L) roughly corresponds to

2223-430: The first sources of iron ore is bog iron . Bog iron takes the form of pea-sized nodules that are created under peat bogs at the base of mountains. Places with plentiful raw materials and little economic development often show a phenomenon known as " Dutch disease " or the " resource curse ", which occurs when the economy of a country is mainly based upon its exports because of its method of governance. An example of this

2280-473: The form of uric acid. Tadpoles excrete ammonia, but shift to urea production during metamorphosis . Despite the generalization above, the urea 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 can be irritating to skin, eyes, and the respiratory tract. Repeated or prolonged contact with urea in fertilizer form on

2337-570: The humans of that time period were able to excavate. The nickel content of the meteoric iron made it not necessary to be heated up, and instead, it was hammered and shaped into tools and weapons. Iron ore can be found in a multitude of forms and sources. The primary forms of iron ore today are Hematite and Magnetite . While iron ore can be found throughout the world, only the deposits in the order of millions of tonnes are processed for industrial purposes. The top five exporters of Iron ore are Australia, Brazil, South Africa, Canada, and Ukraine. One of

Biuret - Misplaced Pages Continue

2394-519: The involvement of living organisms. The results of this experiment implicitly discredited vitalism , the theory that the chemicals of living organisms are fundamentally different from those of inanimate matter. This insight was important for the development of organic chemistry . His discovery prompted Wöhler to write triumphantly to Jöns Jakob Berzelius : In fact, his second sentence was incorrect. Ammonium cyanate [NH 4 ] [OCN] and urea CO(NH 2 ) 2 are two different chemicals with

2451-408: The mass of the protein, which can be observed in protein mass spectrometery . For this reason, pure urea solutions should be freshly prepared and used, as aged solutions may develop a significant concentration of cyanate (20 mM in 8 M urea). Dissolving urea in ultrapure water followed by removing ions (i.e. cyanate) with a mixed-bed ion-exchange resin and storing that solution at 4 °C

2508-494: The material in the Earth's inner and outer core . The iron that was initially used as early as 4000 BC was called meteoric iron and was found on the surface of the Earth. This type of iron came from the meteorites that struck the Earth before humans appeared, and was in very limited supply. This type is unlike most of the iron in the Earth, as the iron in the Earth was much deeper than

2565-409: The nail. This drug (as carbamide peroxide ) is also used as an earwax removal aid. Urea has also been studied as a diuretic . It was first used by Dr. W. Friedrich in 1892. In a 2010 study of ICU patients, urea was used to treat euvolemic hyponatremia and was found safe, inexpensive, and simple. Like saline , urea has been injected into the uterus to induce abortion , although this method

2622-402: The nephrons, thus raising the osmolarity in the medullary interstitium surrounding the thin descending limb of the loop of Henle , which makes the water reabsorb. By action of the urea transporter 2 , some of this reabsorbed urea eventually flows back into the thin descending limb of the tubule, through the collecting ducts, and into the excreted urine. The body uses this mechanism, which

2679-404: 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 p K b 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

2736-412: The plant through its roots. In some soils, the ammonium is oxidized by bacteria to give nitrate ( NO − 3 ), which is also a nitrogen-rich plant nutrient. The loss of nitrogenous compounds to the atmosphere and runoff is wasteful and environmentally damaging so urea is sometimes modified to enhance the efficiency of its agricultural use. Techniques to make controlled-release fertilizers that slow

2793-529: The price of natural gas to increase by 50% in 2022. While pottery originated in many different points around the world, it is certain that it was brought to light mostly through the Neolithic Revolution . That is important because it was a way for the first agrarians to store and carry a surplus of supplies. While most jars and pots were fire-clay ceramics , Neolithic communities also created kilns that were able to fire such materials to remove most of

2850-462: The release of nitrogen include the encapsulation of urea in an inert sealant, and conversion of urea into derivatives such as urea-formaldehyde compounds, which degrade into ammonia at a pace matching plants' nutritional requirements. Urea is a raw material for the manufacture of formaldehyde based resins , such as UF, MUF, and MUPF, used mainly in wood-based panels, for instance, particleboard , fiberboard , OSB, and plywood . Urea can be used in

2907-455: The runoff from fertilized land may play a role in the increase of toxic blooms. The substance decomposes on heating above melting point, producing toxic gases, and reacts violently with strong oxidants, nitrites, inorganic chlorides, chlorites and perchlorates, causing fire and explosion. Urea was first discovered in urine in 1727 by the Dutch scientist Herman Boerhaave , although this discovery

SECTION 50

#1732868827995

2964-436: The same empirical formula CON 2 H 4 , which are in chemical equilibrium heavily favoring urea under standard conditions . Regardless, with his discovery, Wöhler secured a place among the pioneers of organic chemistry. Uremic frost was first described in 1865 by Harald Hirschsprung , the first Danish pediatrician in 1870 who also described the disease that carries his name in 1886. Uremic frost has become rare since

3021-469: The skin may cause dermatitis . High concentrations in the blood can be damaging. Ingestion of low concentrations of urea, such as are found in typical human urine , are not dangerous with additional water ingestion within a reasonable time-frame. Many animals (e.g. camels , rodents or dogs) have a much more concentrated urine which may contain a higher urea amount than normal human urine. Urea can cause algal blooms to produce toxins, and its presence in

3078-415: The trimer of 1,6-hexamethylene diisocyanate is also known as HDI-biuret. In the anhydrous form, the molecule is planar and unsymmetrical in the solid state owing to intramolecular hydrogen bonding. The terminal C–N distances of 1.327 and 1.334 Å are shorter than the internal C–N distances of 1.379 and 1.391 Å. The C=O bond distances 1.247 and 1.237 Å. It crystallizes from water as the monohydrate. Biuret

3135-417: The type [M(urea) 6 ] . Urea reacts with malonic esters to make barbituric acids . Molten urea decomposes into ammonium cyanate at about 152 °C, and into ammonia and isocyanic acid above 160 °C: Heating above 160 °C yields biuret NH 2 CONHCONH 2 and triuret NH 2 CONHCONHCONH 2 via reaction with isocyanic acid: At higher temperatures it converts to

3192-439: Was aided by Carl Wilhelm Scheele 's discovery that urine treated by concentrated nitric acid precipitated crystals. Antoine François, comte de Fourcroy and Louis Nicolas Vauquelin discovered in 1799 that the nitrated crystals were identical to Rouelle's substance and invented the term "urea." Berzelius made further improvements to its purification and finally William Prout , in 1817, succeeded in obtaining and determining

3249-449: Was found to form crystals that increase drug transfer without adverse toxic effects on vascular endothelial cells . Urea labeled with carbon-14 or carbon-13 is used in the urea breath test , which is used to detect the presence of the bacterium Helicobacter pylori ( H. pylori ) in the stomach and duodenum of humans, associated with peptic ulcers . The test detects the characteristic enzyme urease , produced by H. pylori , by

#994005