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Isocyanic acid

 

 
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Isocyanic acid
 
 
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Isocyanic acid is an inorganic compound
Inorganic compound

Traditionally, inorganic compounds are considered to be of a mineral, not biological, origin. Complementarily, most organic compounds are traditionally viewed as being of biological origin....
 with the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 HNCO, discovered in 1830 by Liebig and Wöhler
Friedrich Wöhler

Friedrich W?hler was a Germany chemist, best-known for his synthesis of urea, but also the first to isolate several chemical elements....
. This colourless substance is volatile and poisonous, with a boiling point
Boiling point

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
 of 23.5 °C. Isocyanic acid is the simplest stable chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 that contains carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
, hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
, nitrogen
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
, and oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
, the four most commonly-found elements in organic chemistry
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 and biology.

>

HNCO also can be made by the high-temperature thermal decomposition of cyanuric acid
Cyanuric acid

Cyanuric acid or 1,3,5-triazine-2,4,6-triol is a chemical compound with the chemical formula 3. Like many industrially useful chemicals, this triazine has many synonyms....
, a trimer.

Isocyanic acid hydrolyses
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
 to carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 and ammonia
Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
:

HNCO + H2O ? CO2 + NH3


At sufficiently high concentrations, isocyanic acid oligomerizes to give cyanuric acid and cyamelide
Cyamelide

Cyamelide is an amorphous white solid x and is the polymerisation product of cyanic acid together with its cyclic trimer cyanuric acid. It is a porcelain-like white substance which is absolutely insoluble in water....
, a polymer.






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Encyclopedia


Isocyanic acid is an inorganic compound
Inorganic compound

Traditionally, inorganic compounds are considered to be of a mineral, not biological, origin. Complementarily, most organic compounds are traditionally viewed as being of biological origin....
 with the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 HNCO, discovered in 1830 by Liebig and Wöhler
Friedrich Wöhler

Friedrich W?hler was a Germany chemist, best-known for his synthesis of urea, but also the first to isolate several chemical elements....
. This colourless substance is volatile and poisonous, with a boiling point
Boiling point

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
 of 23.5 °C. Isocyanic acid is the simplest stable chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 that contains carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
, hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
, nitrogen
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
, and oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
, the four most commonly-found elements in organic chemistry
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 and biology.

Preparation and reactions


Isocyanic acid can be made by protonation of the cyanate anion, such as from salts like potassium cyanate
Potassium cyanate

Potassium cyanate is an inorganic compound with the chemical formula KOCN. It is the conjugate base of cyanic acid, HOCN. This reagent is used to prepare herbicide....
, by either gaseous hydrogen chloride
Hydrogen chloride

The Chemical compound hydrogen chloride has the chemical formula HydrogenChlorine. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity....
 or acids such as oxalic acid
Oxalic acid

Oxalic acid is the chemical compound with the chemical formula H2C2O4. This dicarboxylic acid is better described with the formula HOOCCOOH....
.

H+ + NCO- ? HNCO


HNCO also can be made by the high-temperature thermal decomposition of cyanuric acid
Cyanuric acid

Cyanuric acid or 1,3,5-triazine-2,4,6-triol is a chemical compound with the chemical formula 3. Like many industrially useful chemicals, this triazine has many synonyms....
, a trimer.

Isocyanic acid hydrolyses
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
 to carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 and ammonia
Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
:

HNCO + H2O ? CO2 + NH3


At sufficiently high concentrations, isocyanic acid oligomerizes to give cyanuric acid and cyamelide
Cyamelide

Cyamelide is an amorphous white solid x and is the polymerisation product of cyanic acid together with its cyclic trimer cyanuric acid. It is a porcelain-like white substance which is absolutely insoluble in water....
, a polymer. These species usually are easily separated from liquid- or gas-phase reaction products. Dilute solutions of isocyanic acid are stable in inert solvents, e.g. ether and chlorinated hydrocarbons.

Isocyanic acid reacts with amine
Amine

Amines are organic compounds and functional groups that contain a base nitrogen atom with a lone pair. Amines are derivative s of ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups....
s to give urea
Urea

Urea is an organic compound with the chemical formula 2carbonoxygen.Urea is also known by the International Nonproprietary Name carbamide, as established by the World Health Organization....
s:
HNCO + RNH2 ? RNHC(O)NH2.


HNCO adds across electron-rich double bonds, such as vinylethers, to give the corresponding isocyanates.

Isomers


Low-temperature photolysis of solids containing HNCO has been shown to make H-O-CN, cyanic acid, which is a tautomer
Tautomer

Tautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. Commonly this reaction results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond....
 of isocyanic acid. Pure cyanic acid has not been isolated, and isocyanic acid is the predominant form in all solvents. Note that sometimes information presented for cyanic acid in reference books is actually for isocyanic acid.

Cyanic and isocyanic acids are isomer
Isomer

In chemistry, isomers are compounds with the same molecular formula but different structural formulae. Isomers do not necessarily share similar properties unless they also have the same functional groups....
s of fulminic acid
Fulminic acid

Fulminic acid is a compound with a molecular formula HCNO. This substance was discovered in 1824 by Justus von Liebig. It is an organic acid and an isomer of isocyanic acid, discovered one year later by Friedrich Woehler....
 (H-C=N-O), an unstable compound.

See also

  • Cyanate
    Cyanate

    The cyanate ion is an anion consisting of one oxygen atom, one carbon atom, and one nitrogen atom, [OCN]-, in that order, and possesses 1 unit of negative electric charge, borne mainly by the nitrogen atom....


Further reading


  • Handbook of Chemistry and Physics, 65th. Edition, CRC Press (1984)


External links

  • from NIST Chemistry WebBook (accessed 2006-09-09)