The condensation reaction of α-naphthylisocyanate with n-butanol has been studied in toluene and in bis(2-methoxyethyl) ether (diglyme) by IR spectroscopy at different temperatures (20–60°C). A kinetic study shows that it is first order with respect to each reactant even when the reaction is catalyzed by tin octoate. A general mathematical treatment indicates that secondary reactions may occur in some conditions of temperature, solvent and catalyst, but do not take place in our system. The activation enthalpy and entropy have been determined.