Chlorosulfonyl Isocyanate

[1189-71-5]CClNO3S 141.53 (most chemically reactive isocyanate;1 CSI can undergo two types of nucleophilic addition, namely to the carbonyl carbon and to the sulfur of the sulfonyl chloride; the isocyanate portion can undergo formal cycloaddition) Alternate Name: CSI. Physical Data: mp −44 to −43 °C; bp 107–108 °C/760 mmHg, 38 °C/50 mmHg; d420 = 1.626 g cm−3; nD27 = 1.4435. Solubility: soluble in most organic solvents; reacts violently with water. Form Supplied in: colorless liquid; widely available. Handling, Storage, and Precautions: reacts explosively with water to form sulfamic acid, hydrogen chloride, and carbon dioxide; fumes slightly in air, has a choking smell, and undergoes thermal decomposition only above about 300 °C. Glass stoppers of bottles used for storage of CSI stick fast after a short time, even when covered with silicone grease, so that polyethylene bottles with screw caps are best for longer storage times (a few weeks); can be kept indefinitely in sealed glass ampules. Suitable solvents include saturated aliphatic hydrocarbons (more or less limited solubility below 0 °C), aromatic hydrocarbons such as benzene and toluene, chlorinated hydrocarbons such as CH2Cl2, CHCl3, CCl4, and chlorobenzene, diethyl ether, diisopropyl ether, and acetonitrile. Liquid sulfur dioxide is particularly favorable, since it increases the reactivity of CSI still further. Solvents such as acetone and ethyl acetate can be used to a limited extent, but only at low temperatures.