1H NMR analysis of the tolylene-2,4-diisocyanate – methanol reaction

Tolylene-2,4-diisocyanate 1 reacts with methanol through two simultaneous paths in the polyurethane reaction, which involve two different intermediates – tolylene-4-carbamatic-2-isocyanate 2 and tolylene-2-carbamatic-4- isocyanate 3, and the final product is tolylene-2,4-dicarbamate 4. The –CH3 chemical shifts in benzene ring in compounds 1, 2, 3 and 4 can be easily tested and well distinguished, through which those four compounds are quantified and their kinetics are investigated. It shows that four rate constants for the tolylene-2,4-diisocyanate – methanol reaction in CCl4 at 50℃ are k1=9.6×10-2 h-2•mol-2•min-1, k2=1.4×10-2 h-2•mol-2•min-1, k3=4.0×10-3 h-2•mol-2•min-1, k4=1.4×10-3 h-2•mol-2•min-1. (k1 is the reaction rate constant from compound 1 to 2; k2 is the reaction rate constant from compound 1 to 3; k3 is the reaction rate constant from compound 3 to 4; k4 is the reaction rate constant from compound 2 to 4)