Catalysis in competing isocyanate reactions. II. Competing phenyl isocyanate reactions catalyzed with N,N′,N″‐pentamethyldipropylenetriamine

Abstract

AbstractThe kinetics of the N,N′,N″‐pentamethyl dipropylene triamine (PMPT)‐catalyzed reaction of phenyl isocyanate with n‐butanol was studied in acetonitrile between 26.5 and 50°C by measuring the NCO disappearance as well as the formation of the various reaction products by means of the standard dibutylamine back‐titration method and the high‐performance liquid chromatography (HPLC) method. The resulting products from the phenyl isocyanate and n‐butanol reaction were found to be N‐butyl phenylcarbamate, N‐butyl‐α,γ‐diphenylallophanate, and triphenylisocyanurate. Trimer formed at the expense of carbamate formation even at a high OH/NCO ratio. Allophanate appeared to be an intermediate in the formation of trimer. PMPT was found to be a urethane and trimerization catalyst for the model reaction of phenyl isocyanate with n‐butanol in acetonitrile. The PMPT‐catalyzed reaction of phenyl isocyanate with n‐butanol in the presence of water in acetonitrile at 50°C was also investigated. The resulting reaction products consisted of n‐butyl phenylcarbamate, n‐butyl‐β,γ‐diphenylallophanate, triphenylisocyanurate, sym‐triphenylbiuret, and N,N′‐diphenylurea. The presence of water retarded the disappearance of NCO groups as well as the trimer formation. Aniline (the product of phenyl isocyanate and water) was detected in the reaction of equivalent amounts of phenyl isocyanate and water in acetonitrile.