Iso nitriles

The iso-nitrile may be removed by the following procedure. Shake the crude (undistilled) n-butyl cyanide twice with about half its volume of concentrated hydrochloric acid and separate carefully after each washing then wash successively with water, saturated sodium bicarbonate solution and water. Dry with anhydrous calcium chloride or anhydrous calcium sulphate, and distil. Collect the pure n-butyl cyanide at 139-141°. If a fraction of low boiling point is obtained (because of incomplete drying), dry it again with anhydrous calcium sulphate and redistil. The yield is 95 g. 

It is important to mix the mandelonitrile with hydrochloric acid immediately it has been separated from the water. Standing results in rapid conversion to the acetal of benzaldehyde and mandelonitrile C(H,CH[OCH(CN)C H,] and/or the iso-nitrile the yield of mandelic acid will, in consequence, be reduced. 

With tertiary phosphines, phosphites and iso-nitriles, the substitution of the carbonyl groups in Co4(CO)i2 and Rh4(CO)i2 occurs very easily up to the tri-substituted complex. It is sufficient to add slowly at room temperature a solution of the ligand to a solution of the dodecacarbonyl ... 

DMF at room temperature. Solid-phase-mediated iso nitrile synthesis under microwave irradiation led to much faster reactions and in many cases improved yields therefore, allowing rapid access to this important class of compounds, amenable for a broad range of subsequent synthesis. 

Cavell investigated the reactivity of 132 and 133 towards a wide range of substrates including THF, nitriles, iso-nitriles, amines, alcohols, alkyl halides, carbon dioxide, isocyanates, and carbodiimides. Three classes of reactivity emerged (i) base adduct formation (ii) 1,2-addition across the M=C bond (iii) [2 + 2] cycloadditions across the M=C double bond.62,63... 

HFA and cyanotrimethylsilane react stoichiometrically with formation of the substituted cyanhydrin 9 (775). Increasing the molar ratio of the reactants to 4 1 yields, in addition to 9, compound 10, with nitrile-isonitrile equilibrium competing with direct attack of HFA (242). The five-membered ring is also formed in the reaction of organic iso-nitriles with HFA (188). The same structural feature in addition to insertion has been found when triethylamine is present as a catalyst, as well as minor amounts of 9 (83, 242). 

Hofmann s Iso-cyanide or Iso-nitrile Reaction.— As the iso-cyanides have a very characteristic odor, their formation is easily detected and the reaction is used as a test for primary amines. 

It was discovered by Hofmann and is therefore known as the Hofmann iso-cyanide or iso-nitrile reaction. In this connection the other tests for primary, secondary and tertiary amines should be recalled (pp. S9-6i). 

Iso-nitriles, Carbylamines.— The alkyl cyanides because of tlieir relations to acids are known as acid nitriles methyl cyanide by hydrolysis yields acetic acid and it is thus known also as acetic nitrile. The iso-cyanides being isomeric with the nitriles are also termed isonitriles. Another name is sometimes used because of. their amine relationship, viz., carbyl-amine methyl iso-cyanide, CH3—NC, being methyl carbylamine. The lower alkyl-iso-cyanides are liquids with a very strong disagreeable odor. They are readily hydrolized by water but form salts with hydrochloric acid and also with silver cyanide. 

The isomerism existing in the case of cyanides or nitriles and isocyanides or iso-nitriles, which we have just discussed, is found also, in part, in their oxidation products the iso-cyanates and in analogous sulphur compounds the thio-cyanates and iso-thio-cyanates. We have referred to the fact that hydrocyanic acid like hydrochloric acid yields an oxygen acid which though unknown itself is represented by well known salts. 

In this reaction the nitrogen changes from tri-valent to penta-valent, or according to the other view in regard to the constitution of iso-cyanides (p. 71), the carbon changes from tetravalent to bivalent. It will be recalled that this reaction has been met with before (p. 70), and is known, as Hofmann s iso-nitrile reaction. It is a test for primary amines as it is necessary for the amine to have two hydrogen atoms in order to withdraw two chlorine atoms from the chloroform. The characteristic odor of the iso-nitrile makes the reaction a distinctive test, for either a primary amine or for chloroform. 

From Ammonia.—A third method for the synthesis of hydrocyanic acid supports the constitution of an iso-cyanide with the linkage of hydrogen to nitrogen. The Hofmann iso-nitrile reaction (p. 71) consists in the formation of iso-cyanides (iso-nitriles) by the reaction between chloroform and primary amines in the presence of an alkali. 

Nitriles from Iso-thio-cyanates.— The nitriles may also be made from iso-thio-cyanates (p. 73). When these are heated with copper the sulphur is eliminated and the iso-cyanides ox iso-nitriles are obtained and these iso-cyanides are transformed into the cyanide or nitrile. 

In the aromatic series the direct conversion of acid amides into acid nitriles does not take place readily but the acid itself is made from the acid amide by the reverse process as indicated above, viz., by hydration to the ammonium salt of the acid, which then yields the acid. A related method, however, is used for preparing acids from anilides of formic acid. Aniline being an ammonia compound yields acid-amidelike products with aliphatic acids, e.g. acet anilide, CH3—CO—NH— CeHs (p. 556). Such a compound can not, however, lose water in the same way as the acid amide in the above reaction for the ammonia residue in an anilide contains only one hydrogen. Nevertheless anilides lose water but in a different way. In the case of the anilide of formic acid, i.e. formanilide, H—CO—NH—CeHs, the loss of water results in a compound in which the carbon and nitrogen remain linked to the benzene ring and an iso-cyanide or iso-nitrile is formed. The isonitrile is readily converted into the nitrile and the acid may then be obtained from that. 

Loss of PhH by reductive elimination, binding of substrate via the iso-nitrile C, cyclometallation of the ArCH3 group, migratory insertion involving the isonitrile, isomerization and reductive elimination of the product. 

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