synopsisA study has been conducted of the kinetics of the reactions of primary and secondary alcohols with phenyl isocyanate in the presence of metal catalysts. It has been determined that the type and concentration of metal catalyst, the structure of the alcohols, and the type of solvent play an important role in the reaction rates and ratios of rate constants. Catalysis by lead naphthenate increased the reaction rates of 2-methoxy-lpropanol and 1-methoxy-2propanol more than 3-methoxy-1-propanol, whereas catalysis by dibutyltin dilaurate enhanced the reaction rates of 3-methoxy-1-propanol more than those of 2-methoxy-1-propanol and of 1-methoxy-2-propanol. Dibutyltin dilaurate has been found to impart a high ratio of Kprimsry/Kseoondary, where the primary alcohol was bmethoxy-1-propanol and the secondary alcohol was 1-methoxy-2-propanol. Determinations of mixtures in toluene solutions containing up to 757, of 3-methoxy-1-propanol were made with good accurecy.

synopsisAs part of an investigation for evidence of isocyanate-catalyst and alcohol-catalyst complex formations, determinations of molecular weights were made by means of the freezing point depression of benzene solutions. Mixtures of 1-methoxy-2propanol and dibutyltin dilaurate and mixtures of 1-methoxy-%propano1 and triethylamine both gave strong evidence of the formation of complexes. Complex formations were also detected when the alcohol was replaced by phenyl isocyanate. Significantly larger concentrations of the catalyst were involved in isocyanate complexes than were shown to be the case with the alcohol complexes. These results appear to be experimental evidence for the previously proposed ternary complex as an intermediate in the metal-catalyzed formation of urethanes. 2883

SynopsisThe mechanism of the catalyzed reaction between alcohols and isocyanates was investigated by means of NMR, infrared, and ultraviolet spectroscopy. The shift of the --OH proton resonance in the N M R spectra indicated the existence of a 1: 1 complex in the system dibutyltin dilaurate (DBTDLp1-methoxy-Zpropanol. Complex formation was also observed when lead naphthenate or triethylamine (TEA) were substituted for the DBTDL. Mixtures of the DBTDLTEA catalysts caused a shift of the -OH proton resonance greater than that observed for either catalyst done. This correlates with the synergistic effect noted when preparing urethanes with a mixture of these catalysts. No direct evidence of alcohol-catalyst complex formation could be obtained by infrared spectroscopy. Efforts were also made to detect complex formation in mixtures of phenyl isocyanate and catalysts. These complexes could not be detected by NMR, infrared, or ultraviolet spectroscopy. Katalysator allein beobachtet wurde. Daa entspricht dem bei der Darstellung vonUrethanen mit einer Katalysatormischung festgestellten synergistischen Effekt. Infrarotspektroskopisch konnte keine direkte Evidens fur Komplexbildung aus Alkohol mid Katalysator erhalten werden. Schliesslich wurde versucht eine Komplexbildung in PhenylisocyanabKatalysatormischungen aufzudecken; es konnten aber weder durch NMR-, noch durch Infrarob, noch durch Ultraviolettspektroskopie Komplexe fesb gestellt werden. Received March 1, 1966 Prod. No. 5181A

SynopsisAlkaline hydrolysis of model carbamates, polyurethanes, and poly(urethane-ureas) has been iuvestigated. The model carbamates were based upon phenyl, benzyl, and cyclohexyl isocyanates. The polyurethanes and poly(urethane-ureas) were prepared from tolylene diisocyanate (TDI ), xylylene diisocyanate (XDI), and 4,4'-dicyclohexylmethane diisocyanate (H,,MDI) and a poly(oxyethy1ene) glycol of 6000 molecular weight. Pseudo-first-order rate constants of hydrolysis were obtained in aqueous pyridine solution a t llO"C, and second-order rate constants were obtained in aqueous KOH solution for the model biscarbamates. Pseudo-first-order rate constants of hydrolysis were obtained in alcoholic KOH solution for the polyurethanes and poly(urethane-ureas). The hydrolysis of the model carbamates showed that the stability increased in the following manner: phenyl < benzyl < cyclohexyl. The pseudo-first-order rate constants were dependent upon the PKb of the corresponding amines. The hydrolysis of the polyurethanes and poly(urethane-ureas) showed that the stability increased in the following manner: aromatic < aralkyl < cycloaliphatic. It was shown that polyurethanes are more susceptible to alkaline hydrolysis than to acidic hydrolysis. INTRODUCTlONThe hydrolytic decomposition of urethanes has been investigated by several According t o the findings of all these authors, the N,Ndisubstituted carbamates were more stable toward alkaline hydrolysis than the singly substituted carbamates. Dittert? carried out a kinetic and mechanistic investigation of the alkaline hydrolysis of some organic carbamates. He found that the aromatic unsubstituted and singly N-substituted carbamates decomposed at a much higher rate than the aliphatic and the N,N-disubstituted aromatic carbamates. For the hydrolysis of the former he proposed an isocyanate intermediate, while for the latter he proposed a carbamic acid intermediate.Wagner and Mennickens compared the stability of aromatic and aliphatic urethanes as well as some allophanates and biurets in aqueous pyridine a t

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