[Chemistry Class Notes] on Urea Pdf for Exam

Urea ([CH_{4}N_{2}O]), also popularly known as Carbamide, is the diamide form of carbonic acid. Urea is widely used as a fertilizer, a feed supplement, and a starting material in the manufacture of drugs and plastics. It is a colorless substance existing in the crystalline form, which melts at 132.7°C (271° F) and decomposes even before the Urea boiling point. Urea is also the chief end product of the metabolic protein breakdown in all mammals and few fishes. It doesn’t just occur in the urine of the mammals but also in their milk, bile, blood, and perspiration. 

 

During the procedure of protein breakdown, all the amino groups ([NH_{2}]) are naturally removed from the amino acids which contain proteins. These groups are further converted into Ammonia ([NH_{3}]), which is toxic to the body. In order to protect the body from it, it is converted to urea by the human liver. The urea is further passed through the kidneys and is excreted in the form of urine. 

 

History and Synthesis of Urea

Urea was separated from urine by Hilaire Marin Rouelle, a French chemist, back in 1773.  Later in 1828, Friedrich Wohler, a German chemist, started its official preparation of Ammonium Cyanate. This process is accepted as a laboratory synthesis of this naturally existing organic compound from all the inorganic materials. Urea is then commercially prepared in larger amounts from both liquid carbon dioxide and liquid ammonia. These materials, when combined under elevated temperature and high pressure to form Ammonium Carbamate, decompose at lower pressure to give water and urea.

 

Urea Structure

Urea is a waste product in the body with no physiological function. It dissolves in the kidney and blood before it is excreted as urine. The organic compound of Urea has two different [NH_{2}] groups that are connected by the carbonyl functional group. Urea is non-toxic, which is why it dissolves in water. Apart from being colorless, it also has no smell.

 

In urea, the carbonyl group is attached to two amide groups. This is where it got the name carbamide, which is formed from carboxylic+amide. A carbonyl group is where a carbon atom is double-bonded to an oxygen atom. An amide group is where a nitrogen atom is attached to two different hydrogen atoms. When you put two such amide groups bonded with the carbonyl group, urea is formed. To write the formula, the atoms that urea contain are:

• 1 Carbon

• 1 Oxygen

• 2 Nitrogen

• 4 Hydrogen

 

Urea structural Formula

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How is Urea Produced?

The kidneys, lungs, and skin are the important excretory organs in the body. In other words, they are the only organs that can remove the toxins and toxic products from the body. The lungs are responsible for getting rid of excess carbon dioxide, while the skin removes excess salts and water. The kidneys, on the other hand, also remove excess salts, water, and Urea. The Urea, which is formed when the dietary proteins are turned into amino acids during digestion, are sent to the liver. The liver breaks down all the excess acids to ammonia and further converts it into urea, which is relatively less toxic.

 

Properties of Urea

Urea consists of Nitrogen, Carbon, and Oxygen. As mentioned, you can find it in the milk, blood, and sweat of mammals. When in concentrated form, it is turned into urine. Urea is basically a crystalline compound whose nitrogen content is around 46%, in the dry state. About 1 million pounds of urea is processed in the United States every year. Most of it is used in fertilizers to make their nitrogen content water-soluble. Urea is also used in plastics and glues, animal feedstock, expensive commercial products, and explosive components. 

 

Urea Uses – What is Urea Used For?

• It is mainly used as a nitrogen release fertilizer to make the product water-soluble.

• Urea is used as a stabilizer in most nitrocellulose explosive products.

• It is used in manufacturing high explosive materials like urea nitrate ([CH_{5}N_{3}O_{4}])

• It is used as an important reagent in lanthanide chemistry.

• It is used in creams/ointments that are used for rehydration.

• It is used in hair removal creams and dish soaps.

• It is used as a browning agent for pretzels.

• It is used in manufacturing melamine.

• It is used to detect the bacteria in the stomach through the urea breath test.

 

Synthetic Urea Definition – How is Urea Formed – Preparation of Urea

In 1828, Urea was first artificially synthesized through a scientific breakthrough from inorganic compounds. The chemical compound urea is made by combining ammonia and carbon dioxide (Ammonium Carbamide)  in high pressure and high-temperature reactor.  

[2NH_{3} + CO_{2} leftrightharpoons  NH_{2}COONH_{4} (ammonium~carbamate)]

[NH_{2}COONH_{4} leftrightharpoons H_{2}O + NH_{2}CONH_{2}~(urea)]

 

The heat then further dehydrates the compound to form Urea, a crystalline compound.

 

Urea is one of the most concentrated nitrogenous fertilizers because of its high nitrogen content and ease of conversion to ammonia in the soil. It’s a low-cost substance that’s used in mixed fertilizers as well as applied directly to the soil or sprayed on foliage. It produces methylene–urea fertilizers with formaldehyde, which release nitrogen slowly, continuously, and consistently, allowing for a full year’s supply to be applied at once. Although urea nitrogen is in a nonprotein form, it can be used by ruminant animals (cattle, sheep), and it can be used to meet a considerable portion of these animals’ protein requirements. The use of urea to create urea-formaldehyde resin is second only to its use as a fertilizer in terms of importance. Barbiturates are also synthesized with large concentrations of urea.

Why is Urea Produced in Large Quantities?

The global urea manufacturing capacity is estimated to be at 220 million tons/year. Why is there such a significant amount of urea produced? The reason is that, aside from ammonia, urea is th
e industrial chemical with the highest nitrogen content and is in high demand as a fertilizer. It decomposes into ammonia (really ammonium ions) and carbon dioxide in the soil. Nitrogen-fixing bacteria convert ammonium to nitrate, which is easily absorbed by plant roots. Aside from its high nitrogen concentration, urea is particularly beneficial because it can be applied as a solid in the form of pellets and because of its very high water solubility, which allows it to be mixed with other plant nutrients in solutions.

Agriculture consumes more than 90% of urea output. The remaining 20 million t is used in animal feed (cattle, for example, can convert it to protein), urea-formaldehyde resins, skincare emollients, and barbituric acid production. Instant-cold packs, in which plastic pouches hold urea and water in separate compartments, are based on urea’s significantly negative heat of solution in water. Intermixing produces short-term cooling for painful joints and muscles when the seal between them is disrupted.

Applications  of Urea

1. Urea is a chemical raw ingredient used to make a variety of products, including polymers, urea-formaldehyde resins, and adhesives.It is also used to make feedstock, glue, fertilizer, commercial products, and resin.

2. Urea can be applied dry to the soil or dissolved and applied through irrigation water for irrigated crops. Urea dissolves in water in its own weight, but as the concentration rises, it becomes more difficult to dissolve. When urea dissolves in water, it becomes endothermic, lowering the temperature of the solution.

3. Urea is a raw material used to make a variety of essential compounds, including:

• Several plastics, particularly urea-formaldehyde resins

• Various adhesives used in marine plywood, such as urea-formaldehyde or urea-melamine-formaldehyde

• Another industrial feedstock is potassium cyanate.

• The explosive urea nitrate.

4. Urea is used in topical dermatological products to help the skin rehydrate. 40 percent urea preparations can also be utilized for non-surgical nail debridement if they are protected by an occlusive bandage. This medication is also used to remove earwax.

5. De-icing using urea is a safe, non-corrosive fertilizer solution. The chemical is simple to apply to runways and walkways, as well as landing gear and other critical sections of an aircraft’s undercarriage that must be corrosion-free at all times. In many regions where extremely corrosive chloride salts cannot be used for de-icing operations, urea is the favored choice.

6. Physicians discovered that urea levels can be used to detect kidney diseases and disorders such acute kidney failure and end-stage renal disease (ESRD). The blood urea nitrogen (BUN) and urine urea nitrogen (UUN) tests, which measure urea nitrogen levels in the blood and urine, are frequently used to evaluate a patient’s kidney function. Increased or decreased urea levels, on the other hand, aren’t always indicative of kidney disease; they could be due to dehydration or an increase in protein consumption.