Studies in the formation of poly(oxazolidones) I. Kinetics and mechanism of the model oxazolidone formation from phenyl isocyanate and phenylglycidyl ether. Selectivity of catalysts

The reaction of phenyl isocyanate with phenylglycidyl ether in the presence of various catalysts served as a model reaction for the preparation of poly(oxazolidones). The type of catalyst used determines the mechanism of the oxazolidone synthesis. In addition to the basic product, oxazolidone, side products may be formed, the most frequent of which is the formation of isocyanurates, which depends upon the temperature and the type of catalyst. The most effective epoxide-soluble catalysts evaluated so far in the preparation of oxazolidones were the complex catalyst AlCl₃-triphenylphosphine oxide and AlCl₃-hexamethylphosphoric triamide. The kinetic study of the oxazolidone formation was carried out by means of HPLC, and the isocyanate and epoxide were separately determined by means of the di-n-butylamine and the perchloric acid methods, respectively. The HPLC method also clearly demonstrated the presence of two isomers, 3-phenyl-5-phenoxymethyloxazolidone-2 and 3-phenyl-4-phenoxymethyloxazolidone-2. The distribution of these isomers, previously reported in the literature, was found to depend upon the temperature and the type of catalyst used.