Reactions of 2,6-Toluene Diisocyanate with Alcohols: Kinetic Studies in the Absence and Presence of Catalysts

The kinetics of the reaction between 2,6-toluene diisocyanate (2,6-TDI) and alcohols with varying carbon chain lengths and a primary or secondary hydroxyl group in the absence and presence of tin(II) 2-ethylhexanoate (TEH) as a catalyst were studied. The alcohols were applied in high molar excess relative to 2,6-TDI to obtain a pseudo-first-order dependence on 2,6-TDI. Based on the kinetic results, it was found that (i) 2,6-TDI reacts faster with alcohols with longer carbon chains than those with shorter ones, (ii) secondary alcohols are approximately 3 times less reactive towards 2,6-TDI than primary ones, and (iii) after the first isocyanate group has been reacted, the reactivity of the remaining isocyanate group decreases. Furthermore, the rate constants were found to depend linearly on catalyst concentration.