Diazonium Salts


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diazonium salts

[‚dī·ə′zō·nē·əm ′sȯls]
(organic chemistry)
Compounds of the type R·X·N:N, where R represents an alkyl or aryl group and X represents an anion such as a halide.

Diazonium Salts

 

organic nitrogenous compounds of the general formula Diazonium Salts (where Ar is an aromatic or heterocyclic radical; X is the residue of a strong acid such as HSO4-, Cl-, or BF4-). Diazonium salts are usually produced by the diazotization reaction: NaNO2 acts on aromatic amines in an excess of strong acid, for example,

Almost all diazonium salts are solids; they are colorless or yellowish and readily soluble in water. They are highly reactive and therefore cannot be stored for long periods in aqueous solutions or as solids. In an acidic medium, diazonium salts break down (slowly in the cold and rapidly upon heating) into oxy compounds, nitrogen, and acid:

In solid form diazonium salts are explosive; they are usually processed in solution or suspension without isolation. Stable diazonium boron fluorides, Diazonium Salts, which are produced by the interaction of an alcohol solution of aromatic amine and fluoboric acid with nitrous acid esters (such as amyl nitrite), are an exception. Stable dry diazonium salts can be produced in the form of double salts (diazoles).

Nitrogen coupling, which is used to produce azo dyes, is the most important reaction of diazonium salts. Other reactions of diazonium salts, such as replacement of the diazo group with hydrogen, halogens, and other substances, are used in technology.

REFERENCES

Vorozhtsov, N. N. Osnovy sinteza promezhutochnykh produktov i krasitelei, 4th ed. Moscow, 1955.
Zollinger, H. Khimiia azokrasitelei. Leningrad, 1960. (Translated from German.)

E. S. LISITSYNA

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The first step in the synthesis of azo dyes is the conversion of amine compounds into diazonium salts.
Here, chemists and related scientists begin to fill that gap by exploring such aspects as attaching organic layers to material surfaces by reducing diazonium salts, analytical methods for characterizing aryl layers, electrografting conductive oligomers and polymers, electronic properties of silicon surfaces modified by aryl diazonium compounds, and various electrochemical strategies for grafting electronic functional molecules to silicon.
It provides guidance on selecting the appropriate aminating agent--whether haloamines, hydroxylamines, diazonium salts, azo compounds, or azides--for different types of carbon nucleophile.