914934-29-5Relevant academic research and scientific papers
Thermally latent reaction of hemiacetal ester with epoxide controlled by Schiff-base-zinc chloride complexes with tunable catalytic activity
Komatsu, Hiroyuki,Ochiai, Bungo,Hino, Tetsuo,Endo, Takeshi
, p. 289 - 297 (2008/10/09)
Schiff-base-zinc chloride complexes (ZnCl2/1R) thermal-latently catalyze the reaction of glycidyl phenyl ether (2) and 1-propoxyethyl-2-ethylhexanate (3) that proceeds at appropriate temperatures for latent curing. This reaction proceeds via the nucleophilic addition of carboxylic acid generated from the thermal dissociation of 3 to 2, which takes place faster than the reaction without ZnCl2/1R. Catalytic activities of ZnCl2/1R, depending on the basicities of the α-diimine ligands controllable by the substituents on the aromatic rings, were evaluated by kinetic parameters; namely the reaction rate constants (k), the activation energies (Ea), and the frequency factors (A). ZnCl2/1Cl bearing the electron-withdrawing chlorine group initiates the reaction above 80 °C, whereas ZnCl2/1OMe bearing the electron-donating methoxy group initiates the reaction above 100 °C. The Ea values in the reactions with ZnCl2/1Cl and ZnCl2/1OMe were estimated to be 52.2 and 177 kJ mol-1, respectively, which agree with the latencies at ambient temperatures. The A values also differ with the catalysts (6.46 × 102 and 2.04 × 1019 L mol-1 s-1 for ZnCl2/1Cl and ZnCl2/1OMe, respectively). The very high A values for the catalysts with electron-donating groups manifest the very good latencies under ambient conditions, in spite of the high activities at elevated temperatures. The coordination behavior of ZnCl2/1R was evaluated by 1H NMR, 13C NMR, 15N NMR, and IR spectroscopies to understand the substituent effects.
