Methyl Isocyanate - Reactions

Reactions

Methyl isocyanate reacts readily with many substances that contain N-H or O-H groups. With water, it forms 1,3-dimethylurea and carbon dioxide with the evolution of heat (325 calories per gram of MIC):

At 25 °C, in excess water, half of the MIC is consumed in 9 min.; if the heat is not efficiently removed from the mixture, the rate of the reaction will increase and rapidly cause the MIC to boil. If MIC is in excess, 1,3,5-trimethylbiuret is formed along with carbon dioxide. Alcohols and phenols, which contain an O-H group, react slowly with MIC, but the reaction can be catalyzed by trialkylamines or dialkyltin dicarboxylate.Oximes, hydroxylamines, and enols also react with MIC to form methylcarbamates. These reactions produce the products described below (Uses).

Ammonia, primary, and secondary amines rapidly react with MIC to form substituted ureas. Other N-H compounds, such as amides and ureas, react much more slowly with MIC.

It also reacts with itself to form a trimer or higher molecular weight polymers. In the presence of catalysts, MIC reacts with itself to form a solid trimer, trimethyl isocyanurate, or a higher molecular weight polymer:

Sodium methoxide, triethyl phosphine, ferric chloride and certain other metal compounds catalyze the formation of the MIC-trimer, while the high-molecular-weight polymer formation is catalyzed by certain trialkylamines. Since the formation of the MIC trimer is exothermic (298 calories per gram of MIC), the reaction can lead to violent boiling of the MIC. The high-molecular-weight polymer hydrolyzes in hot water to form the trimethyl isocyanurate. Since catalytic metal salts can be formed from impurities in commercial grade MIC and steel, this product must not be stored in steel drums or tanks.