Isocyantes

The reaction with iodine isocyante (INCO) produced a mixture of 2-iodoallylic iso-cyantes 23 and 24 [18]. The ratio of 23 and 24 depends on the reaction temperature and the structures of allenes. In the case of 1,1-dimethylallene, the reaction affords preferentially the diiodination product of the unsubstituted C=C bond. 

Reinhard H. Richter, Dow Chemical USA. Freeport. TX. http //www.dow com, Isocyantes, Organic... 

When a toluene solution of a mixture of cyclotrisilane 34 and cyclohexyl isocyanate (or f-butyl isocyante) was heated at 70 °C, cyclic di- and trisiloxanes 37 and 38, i.e. the cyclic dimer and trimer of the silanone 36, were obtained together with the corresponding isonitrile RN=C. The formation of 37 as well as 38 was completely suppressed in the presence of hexamethylcyclotrisiloxane (19 D3) instead, quantitative conversion of 35 into 39, the formal insertion product of the silanone 36 into the Si—O bond of D3, occurred (Scheme 14). Since neither cyclodisiloxane 37 nor cyclotrisiloxane 38 reacted with D3 under the reaction conditions, the possibility that 37 or 38 is the precursor of 39 was ruled out. Whereas the oxidation of 35 with cyclohexyl and t-butyl isocyanates proceeded with exclusive formation of 37 and 38 (as the silicon-containing compounds) the reaction of 35 with phenyl isocyanate resulted in the formation of 37 in low yield. Furthermore, in this case the presence of D3 did not totally suppress the formation of 37. According to the authors, these results indicate that the oxidation of 35 with cyclohexyl and f-butyl isocyanates appears to use other reaction channels than that with phenyl isocyanate. 

TABLE 1. Polymer properties from four 50 minute anionic polymerization reactions using n-hexyl isocyante in THE with sodium A-phenyl benzyl amine as initiator and then quenching for 10 minntes using methacryloyl chloride dissolved in pyridine. 

Varma, D.R., Mulay, S. (2006). The Bhopal accident and methyl isocyante toxicity. In Toxicology of Organophosphate and Carbamate Compounds (R.C. Gupta, ed.), pp. 79-88. Elsevier Academic Press, New York. 

This dimer was thermically (170°C) or catalytically decomposed to 100% methyl isocyante as shown in scheme 221. 

ASTM D 4889-88 Standard Test Method for Polyurethane Raw Materials Determination of Viscosity of Crue or Modified Isocyantes, 2 pp (Conun D-20)... 

Combustible liquid (flashpoint 124°F/52°C Fire Rating 2). Violent reaction with strong oxidizers epoxides, isocyantes. Mixtures with strong reducing agents, including metal... 

Isocyantes and their rimple reaction products have been known since 1849 when Wurtz synthesized the first isocyanate. The great reactivity of the isocyanate was recognized when the correspcmding ureas were formed by reaction with amines. 

Alkyl-, vinyl-, and aryl-substituted acyl azides undergo thermal 1,2-carbon-to-nitrogen migration with extrusion of dinitrogen — the Curtius rearrangement — producing isocyantes. Reaction of the isocyanate products with nucleophiles, often in situ, provides carbamates, ureas, and other A-acyl derivatives. Alternatively, hydrolysis of the isocyanates leads to primary amines. 

Synthetic polymeric adsorbants. D.H. Clarke details the use of polyurethane based forms which can absorb and subsequently desorb a range of volatile organic solvents such as chlorinated and aromatic hydrocarbons, or aliphatic ketones [20]. The precise composition of polyurethane foam has a profound effect on absorption performance. However providing the correct reaction and balance between specific isocyante... 

Alternatively, other methods use a di-isocyante, such as MDI, to react with the diacid-dimide [16]. This defined architecture allows microstruc-tured polymers to be synthesized which can be useful in membrane and other specialty applications. 

Intensification, or minimization (principle 1 listed above), consists of reducing the quantities of hazardous chemicals in the plant or combining unit operations (also known as telescoping operations). "What you don t have can t leak" is the bus word. Reduced inventory of methyl isocyante at the Bhopal Union Carbide plant could have reduced the intensity of the accident. 

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