Methyl isocyanate reactions with water

The reactions with l-Iithio-2-butyI- and l-Iithio-2-phenyI-l,2-dihydro-pyridines have. been described with several other reagents including isocyanates, esters, and diethyl chlorophosphate.147 A less familiar adduct from 10-methyl-10//-pyrido[3,2-ft][l,4]benzothiazine and butyllithium has also been tested for reaction with water, deuterium oxide, and diethyl chlorophosphate.148... 

A 15.7 g (0.1 mol) of 2,6-dihydroxy methylpy rid in e hydrochloride are suspended in 176 ml of acetonitrile, and 20fi ml (0.15 mol) of triethylamine are added to the suspension. Thereafter 13 ml (0.22 mol) of methyl isocyanate are added dropwise to the reaction mixture at 20°C to 25°C. The reaction mixture is stirred at 20°C to 30°C for one hour, thereafter boiled for 3 hours, and finally the solvent is evaporated under reduced pressure. 35 to 40 g of a greyish, crystalline residue are obtained, which Is a mixture of 2,6-dihydroxymethylpyridine-bis-(N-methylcarbamate) and triethylamine hydrochloride. The obtained residue is dissolved in 80 ml of hot water, decolorized with 2 g of activated carbon when hot, and filtered after 30 minutes of stirring. The filtrate is cooled, the resulting crystal suspension is stirred at 0°C to 5°C for 3 hours, the solids are filtered off, and dried at 50°C to 60°C. 

Several unsuccessful attempts were made to analyze the fluorophor produced by the reaction of MIC with diacetylmonoxime using HPLC and a multiwavelength fluoroescence detector. Because of a series of analytical problems, a search was initiated for a method that would lend itself to liquid chromatographic analysis more readily. Since methyl isocyanate probably reacts with water according to the following equation ... 

Physicochemical Reactions with MIC MIC can interact with a large number of molecules as well as with itself Indeed, 21 identified (Varadarajan et al., 1985) and almost ten unidentified chemicals (Sriramachari, 2004) were detected in the culprit MIC Tank E-610. An MIC trimer as well as other metabolites of MIC such as dimethyl isocyanurate and 2,4-dione of methyl isocyanate were identified in autopsy samples from Bhopal victims (Chandra et al, 1991, 1994 Saraf et al, 1995). Reaction of MIC with water is important because this will occur whenever MIC comes into contact with a body or environment, as happened in Bhopal. It is important to note that while excess water can neutralize MIC, a small quantity of water is sufficient to generate heat during the reaction, which would lead to vaporization of MIC, as actually happened in Bhopal. Some important interactions of MIC are enumerated below ... 

Poly-AMMO is synthesized via cationic polymerisation from the monomer 3-azidomethyl-methyl-oxetane (AMMO). The polymerisation reaction is quenched with water to get polymer chains with hydroxyl endgroups which enable to react these pre-polymers later with isocyanate for curing reaction. Poly-AMMO is suggested as - energetic binder component in -< composite propellants and is in the scope of actual research. 

In 1984, one of the most notable process incidents occurred in Bhopal, India, at a plant owned by Union Carbide. On December 3, 1984, methyl isocyanate (MIC) was vented to the atmosphere from a vent gas scrubber after a run away reaction overwhelmed the scrubber. It is reported that more than 2500 people died and 20,000 people were injured as a result of exposure to MIC. The subsequent investigation showed that the run away reaction occurred in the MIC tanks after water was reportedly intentionally added to the tank. The safety systems, a pressure relief valve, a vent gas scrubber, and a flare were reportedly poorly maintained. The relief valve worked to vent the pressure, but the scrubber was overwhelmed, and the flare was down for maintenance. This incident highlighted several loss prevention areas that needed improvement. The first was mechanical integrity. No strong preventive maintenance effort appeared to be in place. The second was emergency preparedness and response. It appears that while the plant was built 1.5 miles away from the community, zoning problems allowed the community to expand to the plant limits. It does not appear that much effort was made to work with the community on commimication/notification or evacuation needs. ... 

Figure 1.4 shows a simplified flow chart of the process. An intermediate in the processes is methyl isocyanate (MIC), which was stored in a series of tanks partially underground and equipped with cooling systems and a series of safety control devices (Figure 1.5). In fact, MIC is a highly toxic (maximum exposure TLV-TWA, during an 8-hour period is 20 parts per billion), flammable gas that has a boiling point near to ambient temperature and gives a runaway reaction vdth water unless chilled below 11 °C. Table 1.4 gives the list of MIC safeguards.

Evidence that chemical reaction has taken place with wood cell wall hydroxyl groups is evident from the infrared (IR) spectra of methyl isocyanate-modified southern pine (Figure 3). All samples run in the IR were first milled to pass a 40-mesh screen and extracted first with benzene/ethanol (2/1, v/v) followed by water in a Soxhlet extractor. Any unreacted reagent and isocyanate homopolymer formed during the reaction with wood would be removed by this extraction procedure. The spectrum for unreacted... 

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