Urea

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Urea
Urea ball and stick.png
Names
IUPAC name
Urea
Systematic IUPAC name
Carbonic diamide
Other names
Carbamide
Carbonyl diamide
Carbonyldiamine
Diaminomethanal
Diaminomethanone
Properties
CH4N2O
(NH2)2CO
Molar mass 60.06 g/mol
Appearance White solid
Density 1.32 g/cm3
Melting point 133–135 °C (271–275 °F; 406–408 K)
Boiling point Decomposes
107.9 g/100 ml (20 °C)
167 g/100 ml (40 °C)
251 g/100 ml (60 °C)
400 g/100 ml (80 °C)
Solubility Soluble in glacial acetic acid
Insoluble in benzene, toluene, xylene
Solubility in acetonitrile 0.4 g/100 ml
Solubility in ethanol 5 g/100 ml
Solubility in glycerol 50 g/100 ml
Solubility in methanol 16.6 g/100 ml
Thermochemistry
-79.634 kcal/mol
Hazards
Safety data sheet Sigma-Aldrich
Lethal dose or concentration (LD, LC):
8500 mg/kg (oral, rat)
Related compounds
Related compounds
Biuret
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Urea or carbamide, is an organic compound commonly used as a fertilizer. It has the chemical formula (NH2)2CO. Urea was the first organic chemical produced from inorganic chemicals, a breakthrough in chemistry, which proved organic substances can be produced from inorganic substances, disproving the notion of vitalism.

Properties

Chemical

Thermal decomposition of urea produces ammonium isocyanate, who in turn yields isocyanuric acid.

NH2CONH2 → NH4NCO → HNCO + NH3

Urea is a weak organic base. It forms salts with strong acids.[1] Despite its two amino groups, it acts as a monoprotic base, only accepting one H+ cation. With diprotic acids such as sulfuric, urea forms two types of salts: monocarbamide dihydrosulfate (carbamonium bisulfate, analogous to inorganic bisulfates) and dicarbamide dihydrosulfate (carbamonium sulfate, analogous to inorganic sulfates).

A frequent contaminant of urea is biuret. A high concentration of biuret mitigates against using urea as a crop fertilizer, but makes it more valuable as an animal feed additive.

Physical

Urea is a white crystalline substance. Its melting point is between 133-135 °C. Urea is soluble in water (107.9 g/100 ml at 20 °C) and when dissolved, it is neutral on the pH scale. Urea is soluble in glycerol (500 g/L) and slightly less soluble in ethanol. Urea is soluble in dimethyl sulfoxide (40 g/100 ml at 20-30 °C, 110 g/100 ml at 90-100 °C). [2]

Availability

Urea is available as a fertilizer, either pure or mixed with other substances. It can be very cheaply purchased online, often at less than $5/kg. Most of the OTC urea is coated with a special coating which slows its release in the soil, to prevent fertilizer burn. Recrystallization is required to remove this coating.

ScienceCompany sells 500g of lab grade urea at 16.95 $.

Ebay has many listings for urea as a lab chemical and as fertilizer

Preparation

Urea was first synthesized by reacting silver cyanate with ammonium chloride.

AgNCO + NH4Cl → (NH2)2CO + AgCl

Industrially it is produced by the thermal decomposition of ammonium carbamate.

It can also be produced from the reaction of phosgene and ammonia

COCl2 + 4 NH3 → (NH2)2CO + 2 NH4Cl

Reactions

Urea forms many adducts with acids and other inorganic and organic compounds. It also acts as a source of ammonia in certain reactions, such as in the production of amides and citrazinic acid.

Projects

Handling

Safety

Urea is non-toxic, though is may cause irritations to sensitive tissues. It may corrode metallic surfaces, even the more resistant forms of stainless steel.

Storage

Urea doesn't require any special storage, and can be safely stored in glass, metal, plastic or ceramic containers.

Disposal

As urea is a good fertilizer, it can be safely dumped in the soil, although it's recommended to avoid dumping it in water reservoirs to prevent the growth on unwanted algae. It can also be used to as a nitrogen source for aerobic bacteria in the conversion of sawdust to compost.

References

  1. https://books.google.com/books?id=Y87aAAAAMAAJ&pg=PA12&lpg=PA12&dq=urea+tartrate&source=bl&ots=PYI2nVC-By&sig=7IbwzeNy5bCPdVWiKmzSzQzq7mw&hl=en&sa=X&sqi=2&ved=0ahUKEwimvPTNmKDLAhXCdx4KHaUGDfkQ6AEIMzAE#v=onepage&q=urea%20tartrate&f=false
  2. http://www.gaylordchemical.com/uploads/images/pdfs/literature/102B_english.pdf Gaylord Chemical Company
  3. Making Urea Nitrate without Nitric Acid
  4. http://link.springer.com/article/10.1007/s11167-005-0579-2#page-1

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