The reaction of o-hydroxybenzyl alcohol with phenyl isocyanate has been investigated in different polar solvents with in situ FT-IR. The rate constants for the reactions of the phenolic hydroxyl group and the aliphatic hydroxyl group were calculated as k 1 and k 2 , respectively. It is found that the phenolic hydroxyl group reacts more easily than the aliphatic hydroxyl group. It is also found that k 1 increases with increasing solvent polarity, while the trend of k 2 is the opposite. Moreover, the reaction kinetics is second-order with respect to toluene, butyl acetate, cyclohexanone and pyridine, but is first-order with respect to NMP and DMF without distinction for the two kinds of hydroxyl groups.
In-situ FT-IR technique is used to investigate the polymerization of propylene oxide with potassium t-butoxide as initiator. The epoxy absorbance at 828 cm-1 is the most useful peaks to monitor the reaction. The absorbance of C-O-C stretching vibration at 1107 cm-1 is very strong and also very useful. Yet, the absorbance of C-H stretching vibration in 3000~2800 cm-1 region is very weak and not reliable for In-situ FT-IR analysis. By monitoring the consumption of propylene oxide, the polymerization rate constant k at 33°C was calculated out and an interesting auto acceleration phenomenon was discovered. Moreover, the chain-transfer process was analyzed by measuring the formation of C=C double bonds, which clarified a former confusion about the course of propylene oxide rearrangement.
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