Isocyanate ($\mathrm{R}-\mathrm{N}=\mathrm{C}=\mathrm{O}$)

An isocyanate bears an $\mathrm{R}-\mathrm{N}=\mathrm{C}=\mathrm{O}$ group. A molecule bearing two such groups can react with a diol to form polyurethane connections.