The amount effect of catalyst on the urethane reaction of o-hydroxybenzyl alcohol

The urethane reaction of o-hydroxybenzyl alcohol with phenyl isocyanate was monitored with in situ FT-IR. Dibutyltin dilaurate was used as catalyst and its amount effect was investigated. It was found that there was an obvious induction period before reaction began. It was interesting that the time of induction period climbed up and then declined with the increase of dibutyltin dilaurate. When the concentration of dibutyltin dilaurate reached 9.58 × 10−5 mol/L, the induction period disappeared completely and hereafter did not appear any more. Furthermore, the urethane reaction kinetics was studied. When the concentration of dibutyltin dilaurate increased, the reaction rate of phenolic group (k1) increased sharply, but the reaction rate of alcoholic group (k2) appeared of little change on the whole. k1 increased about 20-fold, yet k2 increased about 2-fold when the concentration of dibutyltin dilaurate varied from 9.58 × 10−6 mol/L to 1.92 × 10−4 mol/L, which made the value of k1/k2 enlarge.