Isocyanate

Synthesis

The normal industrial route to the manufacture of diisocyanates, is to synthesise the desired molecular structure with phosgene replaces the amine groups with isocyanate groups.^[1]

Common methods for the synthesis of isocyanates in the laboratory are the Curtius rearrangement of acyl azides and the Lossen rearrangement of hydroxamic acids.

Chemistry

The isocyanate group reacts with the hydroxyl functional group to form a 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 polyureas.

The isocyanate group can react with itself. biurets.

Common compounds

  A monofunctional isocyanate of industrial significance is methyl isocyanate (MIC), 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 isophorone diisocyanate (IPDI), and 1.2% was the total for various others.^[1]

Hazards

The reactivity of isocyanates makes them harmful to living tissue. They are toxic and are known to cause asthma in humans, both through inhalation exposure and dermal contact. Exposure to isocyanates and their vapors should be avoided.

See also

• Isothiocyanate

References

1. ^ ^{a b} Randall, D (2002). The Polyurethanes Book. Wiley. ISBN 0-470-85041-8. 

• Health and Safety Executive, website of the UK Health and Safety Executive, useful search terms on this site - isocyanates, MVR, asthma