Studies in the formation of poly(oxazolidones). II. Selectivity of catalysts and kinetics in the synthesis of 2-oxazolidone from butyl isocyanate and phenylglycidyl ether

The reaction of butyl isocyanate with phenylglycidyl ether was selected as a model reaction for the synthesis of aliphatic isocyanate-based poly(2-oxazolidones). The selectivity of different metal halides and aluminum trichloride/triphenylphosphine oxide (AlCl₃ TPPO) and aluminum hexamethylphosphoramide (AlCl₃ HMPA) complexes were investigated for oxazolidone formation. Both FTIR and mass spectrographic methods were employed for characterization of the reaction products. The kinetics of the model reaction was studied using AlCl₃ TPPO in o-dichlorobenzene at 120 and 140°C.     

Cyclotrimerization of butyl and cyclohexyl isocyanate—catalysis and kinetics

The cyclotrimerization of model aliphatic and cycloaliphatic isocyanates (butyl and cyclohexyl isocyanate) was carried out using an ammonium carboxylate and a salicylaldehyde-potassium complex as catalysts. The kinetics of the cyclotrimerization of butyl isocyanate in both 2-ethoxyethyl acetate and dimethylformamide (DMF) using the 2-ethylhexanoate salt of trimethylaminopropanol-2 was found to be of first order with respect to the isocyanate and also of first order with respect to the catalyst. The reaction rate in DMF was considerably greater than in 2-ethoxyethyl acetate, as could be expected. Employing the salicylaldehyde-potassium catalyst, the cyclotrimerization of butyl isocyanate followed second-order kinetics with respect to the isocyanate and first order with regard to the catalyst. Due to the fact that the cyclotrimerization of cyclohexyl isocyanate was found to be slower than that of butyl isocyanate, the cyclotrimerization of this isocyanate was carried out only in DMF using the 2-ethylhexanoate salt of trimethylaminopropanol-2 as the catalyst. The kinetics of this reaction was found to follow second order with respect to the isocyanate and first order with regard to the catalyst. The products of the reactions were identified by IR, ¹H-NMR, and mass spectrometry.