Effects of solvent polarity on the reaction of phenol with tolylene‐2,4‐diisocyanate

Abstract

AbstractUsing tolylene‐2,4‐diisocyanate as standard compound, the relationship between NCO absorbance and concentration was studied with in situ FTIR. The linear relationship appeared correct only for concentrations lower than 0.4 mol L−1. Then, the urethane reaction kinetics of phenol with tolylene‐2,4‐diisocyanate were investigated in different solvents, such as dimethyl sulfoxide, cyclohexanone, n‐butyl acetate, 1,4‐dioxane, and xylene. It showed that solvents largely affected reaction rates. The reaction was largely accelerated in polar solvents, following the order of dimethyl sulfoxide > cyclohexanone > n‐butyl acetate > 1,4‐dioxane > xylene. It was in contrast to the alcohol–diisocyanate reaction. Finally, an appropriate reaction mechanism was proposed. The HO bond in phenol was polarized under the influence of solvents, which made the combination of hydrogen to nitrogen and alkoxyl group to carbenium easier. After that the solvent was dissociated and the carbamate generated. The kinetic equation could be derived as v = k′K·[S:] [ROH]·[R′NCO]. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011