Phenyldiazonium nitrate

When nitrous gases (from arsenious oxide and nitric acid, d. 1 -35) are passed into a well-cooled suspension of aniline nitrate in water, and alcohol and ether are then added gradually, crystalline phenyldiazonium nitrate is obtained. At most only 2 g. of aniline are used, and of the diazonium salt only as much as covers well the tip of a knife-blade is dried on porous plate, after collecting at the pump and washing with alcohol-ether (1 1). 

The nitrate detonates on heating on a spatula or on being struck with a hammer. The chloride is less liable to explode, but it too must not be preserved in the dry state. In general, work with dry diazonium salts must be carried out cautiously. 

On account of their great lability the diazonium salts of the simple primary amines cannot be isolated from aqueous solution. On the other hand, they crystallise from alcohol when ether is added. Since the metallic salts of nitrous acid are insoluble in alcohol, its esters are used instead for diazotisation in alcohol. These esters are hydrolysed by acid with extraordinary rapidity and therefore behave almost like salts (see p. 147). 

The diazonium salts are colourless. Their aqueous solutions react neutral. If the acid is removed from the salts by means of alkali, very unstable diazonium hydroxides result, which can only be demonstrated in the solution during quite a short time. These hydroxides change by addition of alkali and elimination of water into salts of acid diazohydroxides, the so-called diazotates. 

the diazotate solution so obtained is re-acidified, the dia-zonium salt is re-formed  

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The benzene is initially converted to phenylmercuric nitrate which reacts with nitrogen dioxide to yield nitrosobenzene Each of these intermediates has been isolated from the reaction mixture. The nitrosobenzene can react in two wajrs. In nitric acid weaker than 50 per cent, it reacts with 2 moles of nitric oxide to form phenyldiazonium nitrate, a reaction first discovered by Bamberger. The diazonium salt is converted by water to phenol, which is nitrated in steps to the final products. In nitric acid of greater than 50 per cent concentration, the nitrosobenzene is converted directly to p-nitro-phenol without going through the diazonium compound. The p-nitro-phenol is then nitrated further to give the dinitrophenol and picric acid. 

The 5-position of 2-diethylamino-4-methylselenazole is very reactive. Thus it can undergo coupling with phenyldiazonium chloride or even nitration under mild conditions. 

Alkyl and aryl azides are prepared by the nucleophilic displacement by azide ion on halide, sulfate, phenyldiazonium, hydroxyl, nitrate, iodoxy, alkoxy, and tosylate groups [6]. Sodium azide is the most useful and practical reagent. The use of silver azide is not necessary in most cases. Some examples from the literature [8-33] employing these methods are shown in Table I. 

Hydroxypyrazines, or rather tautomeric 2(l//)-pyrazinones, undergo electrophilic substitution such as nitration and bromination ortho or para to the hydroxy or oxo substituent under mild conditions <53JA5517,56JA4071, 78JHC665). When phenyldiazonium chloride is added to 2(l//)-pyr-azinones in alkaline solution, phenylation of the nucleus takes place with evolution of nitrogen in the same substitution pattern as above. 

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