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Isocyanate

Isocyanate is the functional group Functional group

In organic chemistry [i] functional groups are specific groups of atom [i]s within molecule [i]s, that ... 

 of atoms –N=C=O , not to be confused with the cyanate functional group which is arranged as –O–C=N. Any organic compound Organic compound

An organic compound is any member of a large class of chemical compound [i]s whose molecule [i]s contain ... 

 which contains an isocyanate group may also be referred to in brief as an isocyanate. An isocyanate may have more than one isocyanate group. An isocyanate that has two isocyanate groups is known as a diisocyanate. Diisocyanates are manufactured for reaction with polyols in the production of polyurethane Polyurethane

A polyurethane is any polymer [i] consisting of a chain of organic [i] units joined by ... 

s.

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Encyclopedia


Isocyanate is the functional group Functional group

In organic chemistry [i] functional groups are specific groups of atom [i]s within molecule [i]s, that ... 

 of atoms –N=C=O , not to be confused with the cyanate functional group which is arranged as –O–C=N. Any organic compound Organic compound

An organic compound is any member of a large class of chemical compound [i]s whose molecule [i]s contain ... 

 which contains an isocyanate group may also be referred to in brief as an isocyanate. An isocyanate may have more than one isocyanate group. An isocyanate that has two isocyanate groups is known as a diisocyanate. Diisocyanates are manufactured for reaction with polyols in the production of polyurethane Polyurethane

A polyurethane is any polymer [i] consisting of a chain of organic [i] units joined by ... 

s.

Synthesis

The normal industrial route to the manufacture of diisocyanates, is to synthesise the desired molecular structure with amine Amine

Amines are organic compound [i]s and a type of functional group [i] that contain nitrogen [i] as the key ... 

 functional groups at the positions to be occupied by the isocyanate groups. Reaction with phosgene Phosgene

Phosgene is the chemical compound [i] with the formula COCl2. ... 

 replaces the amine groups with isocyanate groups.

Common methods for the synthesis of isocyanates in the laboratory are the Curtius rearrangement Curtius rearrangement

The Curtius rearrangement, as first defined by Theodor Curtius [i], is a chemical reaction [i] that invo ... 

 of acyl azides and the Lossen rearrangement Lossen rearrangement

The Lossen rearrangement [i] is the chemical reaction [i] of a hydroxamic acid [i] 1 with a dehydration ... 

 of hydroxamic acids.

Chemistry

The isocyanate group reacts with the hydroxyl functional group to form a urethane Carbamate

Carbamates or urethane [i]s are a group of organic compound [i]s sharing a common functional group [i] w ... 

 linkage. If a diisocyanate is reacted with a compound containing two or more hydroxyl groups , long polymer chains are formed, known as polyurethanes.

The isocyanate group also reacts with the amine functional group. Reaction between a diisocyanate and a compound containing two or more amine groups, produces long polymer chains known as polyurea Polyurea

A polyurea is an elastomer [i] created by the chemical reaction [i] between an isocyanate [i] and an amine [i]... 

s.

The isocyanate group can react with itself. Aliphatic diisocyanates can form trimers, known as biuret Biuret

Biuret is a a condensation compound of urea [i], equivalent to two molecules of urea less one of ammonia ... 

s.

Common compounds


A monofunctional isocyanate of industrial significance is methyl isocyanate Methyl isocyanate

Methyl isocyanate is an organic compound with the molecular formula C2H3NO, arranged as H3C-N=C=O.... 

 , which is used in the manufacture of pesticides.

The global market for diisocyanates in the year 2000 was 4.4 million tonnes, of which 61.3 % was methylene diphenyl diisocyanate Methylene diphenyl diisocyanate

Methylene diphenyl diisocyanate, most often abbreviated as MDI, is an aromatic [i] diisocyanate [i] ... 

 , 34.1 % was toluene diisocyanate Toluene diisocyanate

Toluene diisocyanate is an aromatic [i] diisocyanate [i]. ... 

 , 3.4 % was the total for hexamethylene diisocyanate Hexamethylene diisocyanate

Hexamethylene diisocyanate is an organic compound in the class known as isocyanate [i]s.... 

  and isophorone diisocyanate Isophorone diisocyanate

Isophorone diisocyanate is an organic compound in the class known as isocyanate [i]s. ... 

 , and 1.2 % was the total for various others.zards


The reactivity of isocyanates makes them harmful to living tissue. They are toxic Toxicity

Toxicity is a measure to the degree to which something is toxic or poison [i]ous. ... 

 and are known to cause asthma Asthma

Asthma is a disease [i] of the respiratory system [i] in which the airways [i] constrict, become in ... 

 in humans, both through inhalation exposure and dermal contact. Exposure to isocyanates and their vapors should be avoided.

See also


  • Isothiocyanate Isothiocyanate

    Isothiocyanate is the chemical [i] group -N [i]=C [i]=S [i], formed by substitut... 




References




External links


  • , from the website of the National Institute for Occupational Safety and Health