Tolylene-2,4-diisocyanate(2,4-TDI) 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-CH_3 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 CCl_4 at 50℃are k_1=9.6×10^(-2)h^(-2)mol^(-2)min^(-1), k_2=1.4×10^(-2)h^(-2)mol^(-2)min^(-1),k_3=4.0×10^(-3)h^(-2)mol^(-2)min^(-1),k_4=1.4×10^(-3)h^(-2)mol^(-2)min^(-1).(k_1 is the reaction rate constant from compounds 1 to 2;k_2 is the reaction rate constant from compounds 1 to 3;k_3 is the reaction rate constant from compounds 3 to 4;k_4 is the reaction rate constant from compounds 2 to 4).
A series of polydimethylsiloxanes containing two primary hydroxyl groups at one single chain end were synthesized by five-step reactions which included esterification,hydroxyl protection,anionic ring-opening polymerization,hydrosilylation and deprotection. The prepared compounds in each step were characterized.The results showed that each step synthesis was successfully carried out and objective products could be achieved.
Meng ZhangJun Ying LiGUO Wei ZhouYuan Juan WuYong Mei XiaTian Duo Li
