Isophorone diisocyanate (IPDI) is an organic compound in the class known as
isocyanateIsocyanate is the functional group of atoms –N=C=O , not to be confused with the cyanate functional group which is arranged as –O–C≡N. Any organic compound which contains an isocyanate group may also be referred to in brief as an isocyanate. An isocyanate may have more than one isocyanate...
s. More specifically, it is an
aliphaticIn organic chemistry, compounds composed of carbon and hydrogen are divided into two classes: aromatic compounds, which contain benzene rings or similar rings of atoms, and aliphatic compounds , which do not contain aromatic rings.
Aliphatic compounds can be cyclic, like cyclohexane, or...
diisocyanate. It is produced in relatively small quantities, accounting for (with
hexamethylene diisocyanateHexamethylene diisocyanate is an organic compound in the class known as isocyanates. More specifically, it is an aliphatic diisocyanate. It is produced in relatively small quantities, accounting for only 3.4% of the global diisocyanate market in the year 2000...
) only 3.4% of the global diisocyanate market in the year 2000. Aliphatic diisocyanates are used, not in the production of
polyurethaneA polyurethane, IUPAC abbreviation PUR, but commonly abbreviated PU, is any polymer consisting of a chain of organic units joined by urethane links...
foam, but in special applications, such as enamel coatings which are resistant to abrasion and degradation from ultraviolet light.
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Isophorone diisocyanate (IPDI) is an organic compound in the class known as
isocyanateIsocyanate is the functional group of atoms –N=C=O , not to be confused with the cyanate functional group which is arranged as –O–C≡N. Any organic compound which contains an isocyanate group may also be referred to in brief as an isocyanate. An isocyanate may have more than one isocyanate...
s. More specifically, it is an
aliphaticIn organic chemistry, compounds composed of carbon and hydrogen are divided into two classes: aromatic compounds, which contain benzene rings or similar rings of atoms, and aliphatic compounds , which do not contain aromatic rings.
Aliphatic compounds can be cyclic, like cyclohexane, or...
diisocyanate. It is produced in relatively small quantities, accounting for (with
hexamethylene diisocyanateHexamethylene diisocyanate is an organic compound in the class known as isocyanates. More specifically, it is an aliphatic diisocyanate. It is produced in relatively small quantities, accounting for only 3.4% of the global diisocyanate market in the year 2000...
) only 3.4% of the global diisocyanate market in the year 2000. Aliphatic diisocyanates are used, not in the production of
polyurethaneA polyurethane, IUPAC abbreviation PUR, but commonly abbreviated PU, is any polymer consisting of a chain of organic units joined by urethane links...
foam, but in special applications, such as enamel coatings which are resistant to abrasion and degradation from ultraviolet light. These properties are particularly desirable in, for instance, the exterior paint applied to aircraft.
Synthesis
There are five steps to the synthesis of pure IPDI:
- Condensation: Conversion of acetone
Acetone is the organic compound with the formula OC2. This colorless, mobile, flammable liquid is the simplest example of the ketones. Owing to the fact that acetone is miscible with water it serves as an important solvent in its own right, typically as the solvent of choice for...
with a catalyst to produce isophorone
- Hydrocyanation: Reaction of the isophorone with hydrogen cyanide
Hydrogen cyanide is a chemical compound with chemical formula HCN. A solution of hydrogen cyanide in water is called hydrocyanic acid. Hydrogen cyanide is a colorless, extremely poisonous, and highly volatile liquid that boils slightly above room temperature at 26 °C...
to form isophorone nitrile
- Reductive amination: Reaction of the isophorone nitrile with ammonia, hydrogen and a catalyst, to form a mixture of isophorone diamine conformers (25/75 cis/trans)
- Phosgenation: Reaction of the isophorone diamine with phosgene
Phosgene is the chemical compound with the formula COCl2. This colorless gas gained infamy as a chemical weapon during World War I, and is also a valued industrial reagent and building block in organic synthesis. In low concentrations, its odor resembles freshly cut hay or grass. Some...
to form a crude mixture containing IPDI conformers (25/75 cis/trans)
- Purification: Distillation of the crude IPDI to extract pure IPDI
Chemistry
IPDI exists in two conformers, cis and trans. Their reactivities are similar. Each conformer is an asymmetrical molecule, and thus has isocyanate groups with different reactivities. The secondary isocyanate group is more reactive than the primary isocyanate group.
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