In Situ FT-IR Studies of the Zirconium (IV) Acetylacetonate Catalyzed Urethane Reaction of Butanediols

A comparative kinetic study of the urethane reactions of phenyl isocyanate and 1,2-, 1,3-, and 1,4-butanediol was carried out in dichloromethane solution with zirconium (IV) acetylacetonate as catalyst. In situ FT-IR was used to follow the kinetics of the reactions at a constant temperature of 15°–30°C. The rate constants for the reaction of the primary hydroxyl group and the secondary hydroxyl group were calculated as k _prim and k _sec, respectively. Analysis of the second-order rate constants of these systems indicated that k _prim follows 1,2-butanediol >1,3-butanediol >1,4-butanediol. The ratio of k _prim/k _sec in 1,2-butanediol was the highest and the order followed was the same as with the reaction rate. Activation energies and Eyring parameters were also determined for the urethane reaction of butanediols.