isocyanatryhmä

The isocyanatryhmä, or isocyanate group, is an organic functional group represented by the structural motif –N=C=O. It consists of a carbon atom double‑bonded to a nitrogen atom and single‑bonded to an oxygen atom, with the carbon atom attached to the rest of the molecule. The group can be derived from the corresponding isocyanic acid, HNCO, by substitution of the hydrogen atom with an organic moiety. Isocyanate groups are often found in molecules such as phosgene, phenyl isocyanate, and various polymer precursors.

Chemically, isocyanates are highly reactive electrophiles. They readily undergo nucleophilic addition reactions, particularly with amines and alcohols, to form ureas and carbamates, respectively. These addition reactions are the basis for the industrial production of polyurethanes, where diisocyanates react with polyols. The reactivity also makes isocyanates useful intermediates in the synthesis of heterocyclic compounds and pharmaceuticals.

Isocyanates are hazardous. Many are lachrymatory and irritant, and exposure can lead to respiratory sensitization. The European Union classifies many diisocyanates and related compounds as sensitizers (Category 9). Protective measures in handling isocyanates include the use of well‑ventilated work areas, personal protective equipment such as gloves, goggles, and full‑sleeved clothing, and, where possible, the substitution of less hazardous reagents. Regulatory limits for occupational exposure vary by region but generally involve very low permissible exposure limits due to their irritant and sensitizing properties.