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The urethane reaction of phenyl isocyanate and 1,2-propylene glycol was investigated with ferric acetylacetonate (Fe(acac)3) as catalyst. The effect of the catalytic properties of Fe(acac)3 on the formation of the urethane bond was evaluated with in situ FT-IR. The influence of the Fe(acac)3 concentration as well as the reaction temperature is discussed. It was observed that there was a turning point in the reaction rate when the temperature decreases, which remained unchanged with variation in Fe(acac)3 concentration. Arrhenius and Eyring parameters of the primary hydroxyl group were determined for the catalyzed reaction. The low-temperature and high-temperature values are surprisingly different. A reasonable reaction mechanism is proposed and the possible active species are discussed, followed by a kinetics and thermodynamics discussion.
Wang et al. (Mon,) studied this question.