Hydroxytelechelic polybutadiene, 11. Kinetics of dibutyltin dilaurate‐catalyzed addition reaction between a hydroxytelechelic polybutadiene and propyl isocyanate

Complexations of 1‐octanol (O) and propyl isocyanate (PI) by dibutyltin dilaurate (DBSnDL) were examined by 350 MHz 1H NMR. Whereas the 1:1 O/DBSnDL complex was easily evidenced, the behaviour of the mixture (1 PI + 1 DBSnDL) suggested slow formation of (a) relatively stable coordination compounds(s). The three alcohol functions of the hydroxytelechelic polybutadiene Arco‐R45M® were found to be equally catalyzed by DBSnDL in the addition with PI in toluene and in the bulk. Linear relationships between initial reaction rates and catalyst concentrations were found only for mole ratios [DBSnDL]/[Arco‐R45M]® < 0,06 and 0,1 in dilute solution and in bulk, respectively. (Acro‐R45M® + PI) additions catalyzed by DBSnDL follow 3rd‐order kinetics. The activation enthalpies and entropies calculated from kinetic data show that, compared to spontaneous addition, catalyzed reaction rates are less sensitive to temperature. Negative activation entropies suggest the existence of relatively stable transition states.