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The isocyanate functional group. In organic chemistry, isocyanate is the functional group with the formula R−N=C=O. Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate.
In this context, the reaction is also known as Saytzeff's isocyanide test. [2] In this reaction, the analyte is heated with alcoholic potassium hydroxide and chloroform. If a primary amine is present, the isocyanide (carbylamine) is formed, as indicated by a foul odour.
In a similar fashion, the intermediate isocyanate can be trapped by tert-butyl alcohol, yielding the tert-butoxycarbonyl (Boc)-protected amine. The Hofmann Rearrangement also can be used to yield carbamates from α,β - unsaturated or α- hydroxy amides [ 2 ] [ 8 ] or nitriles from α,β- acetylenic amides [ 2 ] [ 9 ] in good yields (≈70%).
Isocyanides have also been shown to be a useful reagent in palladium catalysed reactions with a wide variety of compounds being formed using this method. [21] The α position of isocyanides have substantial acidity. For example, benzyl isocyanide has a pK a of 27.4. In comparison, benzyl cyanide has a pK a of 21.9. [22]
Methylene diphenyl diisocyanate (MDI) is an aromatic diisocyanate. Three isomers are common, varying by the positions of the isocyanate groups around the rings: 2,2′-MDI, 2,4′-MDI, and 4,4′-MDI. The 4,4′ isomer is most widely used, and is also known as 4,4′-diphenylmethane diisocyanate. [3] This isomer is also known as Pure MDI.
In nucleophilic substitution reactions cyanate usually forms an isocyanate. Isocyanates are widely used in the manufacture of polyurethane [ 17 ] products and pesticides ; methyl isocyanate , used to make pesticides, was a major factor in the Bhopal disaster .
Cobalt(II) cyanate is the hypothetical inorganic compound with the formula Co(OCN) 2.. The simple cobalt(II) cyanate has not been proven to be made. However, the tetraisocyanatocobalt(II) ion (Co(NCO) 4 2-) is known and its blue color and is used as a qualitative test for cobalt(II) ions.
The activated isocyanate then quickly reacts with the indole ring in an electrophilic aromatic substitution reaction to give the amide in 94% yield, and subsequent steps give dievodamine. [ 29 ] The Curtius rearrangement in the total synthesis of Dievodiamine