Methyl isocyanate reactivity

The plant produced pesticides. An intermediate compound in this process is methyl isocyanate (MIC). MIC is an extremely dangerous compound. It is reactive, toxic, volatile, and flammable. The maximum exposure concentration of MIC for workers over an 8-hour period is 0.02 ppm (parts per million). Individuals exposed to concentrations of MIC vapors above 21 ppm experience severe irritation of the nose and throat. Death at large concentrations of vapor is due to respiratory distress. 

Methyl isocyanate (MIC) is a colorless liquid that must be stored in a cooled enclosure before it is subsequently used in the manufacture of carbamate, a common insecticide. MIC liquid is highly reactive in the presence of water and iron oxide, and it generates heat. In sufficient quantities, this heat may generate vapor, which, as explained previously, is highly toxic. Three adjacent bunkers were used for MIC storage. These were mounted in a berm and a refrigeration coil was used to ensure that the temperature did not exceed 5°C. A vent gas scrubber was used to prevent vapor escape, and despite a low operating pressure, a closed relief... 

Scheme 3.3 Methyl isocyanate, a highly reactive electrophile.

Methyl isocyanate and all isocyanic acid esters are an interesting and highly reactive class of organic compounds, since the isocyanate group (-NC0) reacts readily with a wide variety of compounds as well as with itself to form dimers, trimers, ureas, and carbodi-imides. Methyl isocyanate (MIC) is an intermediate in the preparation of carbamate pesticides and conceivably could be applied to the production of special heterocyclic polymers and derivatives. 

Methyl isocyanate (MIC) is the smallest member of the isocyanate family and the most reactive and toxic of all. MIC was almost unheard of until the fateful night December 3, 1984, when nearly 30 metric tons of this poisonous chemical spewed out of the Union Carbide India Ltd (UCIL) pesticide plant within a period of 45-60 min (Jayaraman, 1984). Bhopal turned into a city of death , wrote the fortnightly India Today (December 30, 1984). The journal Nature (Opinion, 1984) vented its anger thus ... the anguish vividly carried round the world by the television cameras seems not to have matured into the anger, even hysteria, there would have been had the [Bhopal] accident occurred on the edge of a European city - or in Connecticut (the headquarters of Union Carbide was in Danbury, Connecticut, USA). 

By taking apart the cell wall of a modified wood specimen and separating the cell wall components from one another, it is possible to determine the distribution of bonded chemicals in the cell wall polymer. It is more difficult to delignify modified wood than unmodified wood, which means that the lignin has been substituted 122, 127, 128). This is true for wood reacted with both acetic anhydride and methyl isocyanate. Table IX shows that the lignin component is always more substituted than the holocellulose components 128). This would indicate that the lignin is either more accessible for reaction than holocellulose or that it is more reactive than holocellulose. Lignin was found to be more reactive than cellulose toward acetylation 129). 

Pearson PG, Slatter JG, Rashed MS, et al. (1990) S-(N-methylcarbamoyhglutathione A reactive S-linked metabolite of methyl isocyanate. Biochemical and Biophysical Research Communications 166 245-250. 

Regiospecific opening of the epoxide was also achieved by intramolecular delivery of the nucleophile. The alcohol 52 was converted into the reactive intermediate 53 with methyl isocyanate. Cyclisation can occur only to the nearer end of the epoxide (5-exo-tet) to give 54. The stereochemistry is already correct for the SN2 inversion on the epoxide 53. The free OH group is turned into a good leaving group by mesylation without isolation of 54. 

Very recently a rapid method for the preparation of effective polymer-supported isocyanate resins has been reported [31]. Gel-type isocyanate resins tvere generated from aminomethyl resins and inexpensive substrates as alternatives to the commercially available, expensive macroporous polystyrene isocyanate supports. Several isocyanates have been investigated phenyl diisocyanate (PDI) tvas found to be the most efficient. Aminomethyl resin was pre-swollen in NMP, mixed with 2 equiv. PDI, and irradiated at 100 °C for 5 min (Scheme 16.7). Filtration, washing with NMP and DCM and drying under vacuum furnished the corresponding isocyanate resin. The reactivity of this novel gel-type resin was better than that of commercially available methyl isocyanate resins and it was successfully used for purification of a small amide library [31]. 

Methyl isocyanate (MIC), CH3NCO, is a colorless liquid. It is water-reactive, with a specific gravity of 0.96, which is lighter than water. This is the chemical that was released in Bhopal, India, that killed over 3000 people in 1984. Methyl isocyanate is toxic by skin absorption and a strong irritant. The TLV is 0.02 ppm in air. 

Owing to the highly unsaturated isocyanate functional group, methyl isocyanate exhibits high reactivity. It decomposes with water and reacts vigorously with acids, bases, amines, and metals and their salts. 

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