Catalytic Kinetics and Mechanism Transformation of Fe(acac)₃ on the Urethane Reaction of 1,2‐Propanediol with Phenyl Isocyanate

Abstract

The urethane reaction of 1,2-propanediol with phenyl isocyanate was investigated with ferric acetylacetonate (Fe(acac) 3 ) as a catalyst. In situ Fourier transform infrared spectroscopy was used to monitor the reaction, and catalytic kinetics of Fe(acac) 3 was studied. The reaction rates of both hydroxyl groups were described with a second-order equation, from which the influence of the Fe(acac) 3 concentration and reaction temperature was discussed. It was very surprising that the relationship between 1/C and t became constant when reaction temperature increased, which indicated that there was no reactive distinction between the two hydroxyl groups. Although the phenomenon differed with the variation of temperature, it was unaffected by the Fe(acac) 3 concentration. It was attributed to the transformation of the reaction mechanism with the increase in temperature. Furthermore, activation energy (E a ), enthalpy ( H*), and entropy ( S*) for the catalyzed reaction were determined from Arrhenius and Eyring equations, which testified to the transformation of the reaction mechanism. C 2013

Kinetic Investigation of Polyurethane Rubber Formation from CO2‐Containing Polyols

“…1) First, the polyol has both primary and secondary OH functionalities, which can have different kinetic behavior due to steric hindrance. While the reactivity of OH groups with isocyanates is reported to generally decrease in the order primary > secondary > tertiary , differences are not observed in fast reactions, e.g., demonstrated for shorter diols in , . For the examined polyols, no detailed composition data are given.…”

“…The model applied in the previous section includes an overall reaction order but does not distinguish between concentration influences of OH and NCO groups. To gain insights in the contributions of the functional groups to the overall reaction order, the kinetic behavior with varying 3670 -3260 ν(-NH, urethane) [21][22][23][24][25][26][27][28][29][30] 3500 -3190 ν(-OH, polyol) [25,27] 2973 νas(-C-H, methylene) [31,32] 2932 νas(-C-H, methylene) [23,25,33,34] 2894 νs(-C-H, methylene) [34] 2872 νs(-C-H, methylene) [34] 2273 ν(-NCO) [35][36][37] 1738 ν(-C=O, carbonate) [23,24,28] 1720* ν(-C=O, urethane) [26,28,29,35] 1643 ν(-C=O, urea) [26,33,35] 1616* ν(C-N, urea) [30] 1579* ν(N-H, urea) [22,26] 1523* ν(N-H, urethane) [22,24,29] Figure 3. IR spectra of unreacted PU system and reacted PU rubber, isocyanate peak magnified, with vibration assignments, marked (*) wavenumbers are applicable only for the reacted PU rubber system.…”