Carbylamine test

Phenyhsonitrile has a powerful characteristic odor it is used as a qualitative test (the carbylamine test) for chloroform or primary aromatic amines. Chloroform reacts with phenols in alkaline solution to give hydroxyaromatic aldehydes in the Reimer-Tiemann reaction eg, phenol gives chiefly Nhydroxyben2aldehyde and some sahcylaldehyde (11) (see Hydroxybenzaldehydes). 

In the known absence of bromoform, iodoform, chloral, and other halogenated methanes, the formation of phenyhsonitrile with aniline provides a simple and faidy sensitive but nonspecific test for the presence of chloroform, the carbylamine test. Phenyhsonitrile formation is the identification test given in the British Pharmacopoeia. A small quantity of resorcinol and caustic soda solution (10% concentration) added to chloroform results in the appearance of a yellowish red color, fluorescing yeUow-green. When 0.5 mL of a 5% thymol solution is boiled with a drop of chloroform and a small quantity of potassium hydroxide solution, a yellow color with a reddish sheen develops the addition of sulfuric acid causes a change to brilliant violet, which, diluted with water, finally changes to blue (33). 

The idea that dichlorocarbene is an intermediate in the basic hydrolysis of chloroform is now one hundred years old. It was first suggested by Geuther in 1862 to explain the formation of carbon monoxide, in addition to formate ions, in the reaction of chloroform (and similarly, bromoform) with alkali. At the end of the last century Nef interpreted several well-known reactions involving chloroform and a base in terms of the intermediate formation of dichlorocarbene. These reactions included the ring expansion of pyrroles to pyridines and of indoles to quinolines, as well as the Hofmann carbylamine test for primary amines and the Reimer-Tiemann formylation of phenols. 

The product gives a negative carbylamine test and hence contains no significant amount of unchanged primary amine. 

Aminopyrazine undergoes the carbylamine test (397,1171). 2-Amino-3,5,6-trichloropyrazine refluxed with oxalyl chloride in benzene gave... 

Formerly, isonitriles were perhaps best known to many chemists through the indescribably vile odor of volatile members of the series encountered during the Hofmann carbylamine test for primary amines. Over recent years, however, isonitriles have come into their own as versatile synthetic reagents. Several reliable preparative methods now allow ready access to this family of substances and their remarkable chemistry. Biological pathways to isonitriles are also known, the first such substance isolated being the antibiotic xanthocillin (141), isolated from Penicillium notatumP Isonitrile compounds are also isolated fairly frequently from marine sources. ... 

It is often advisable to determine to which class an amine belongs. There are many ways of distinguishing between and separating primary, secondary, and tertiary amines. Only a few will be mentioned here. Acetyl chloride reacts at ordinary temperatures with primary and secondary amines. Heat is evolved, and in most cases solids are formed from liquid amines. Inactivity with this reagent indicates that the substance, previously shown to be an amine, is a tertiary amine. If an acetyl derivative is formed, the carbylamine test (206) is applied. Some of the original substance is warmed with chloroform and an alcoholic solution of potassium hydroxide. The production of the characteristic, disagreeable odor is evidence that the substance is a primary amine. 

Chlorc orm 61 1 446 1 489 Gives carbylamine test with primary amines... 

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