Complex formation between catalysts, alcohols, and isocyanates in the preparation of urethanes

Abstract

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

Fluoropolyethers end-capped by polar functional groups. I. Kinetic approach to the reaction of hydroxy-terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

“…In order to describe our experimental data we considered valid, at first approximation, the mechanism proposed by Frish et al 39,40 and Entelis 41,42 :…”

Kinetic study of the urethane and urea reactions of isophorone diisocyanate

“…Although polyurethane reactions have been subjected to a great number of studies that have suggested various mechanisms for urethane or urea formation, very little attention has been paid to the mechanistic aspects of the autocatalytic effects themselves. 7 In particular, no previously proposed mechanism provides a satisfactory interpretation of the experimental results mentioned previously. In this article, a kinetic study, using quantitative Fourier transform infrared (FTIR) spectroscopy, is performed to gain insight into the mechanism of the autocatalytic effect of the reactions of urethane and urea in the bulk state.…”

Kinetics and mechanisms of catalyzed and noncatalyzed reactions of OH and NCO in acrylic polyol–1,6‐hexamethylene diisocyanate (HDI) polyurethanes. VI

“…For four series of reactions with different reagent concentrations, we have log R 04 ϭ log k ϩ nЈ log͓NCO͔ 04 ϩ hЈ log͓OH͔ 04 ϩ d log͓DBTDL͔ 04 (19) log R 05 ϭ log k ϩ nЈ log͓NCO͔ 05 ϩ hЈ log͓OH͔ 05 ϩ d log͓DBTDL͔ 05 (20) log R 06 ϭ log k ϩ nЈ log͓NCO͔ 06 ϩ hЈ log͓OH͔ 06 ϩ d log͓DBTDL͔ 06 (21) log R 07 ϭ log k ϩ nЈ log͓NCO͔ 07 ϩ hЈ log͓OH͔ 07 ϩ d log͓DBTDL͔ 07 (22) In this experiment, four series of reaction conditions, as shown in (k ϭ 1, 2) are known, after determining the initial reaction rates R 01 , R 02 , and R 03 , and R 04 , reaction orders h', n', and d can be computed. Following the same method as that developed for the study of a noncatalyzed system, the NCO concentration changes as a function of reaction time for each reaction system was measured, and [NCO] as a function of time (Figure 4) was determined.…”