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The diazonium salts stands for “di” means two, “azo” means nitrogen, ”ium” means cation or diazonium compounds, are
the class of organic compounds with general formula R−N2+X− where X is an organic or inorganic anion (for example, Cl–, Br–, BF4–, etc.) and R is an alkyl or aryl group.
Hence, it has two nitrogen atoms with one being positively charged. benzene diazonium hydrogen sulphate (C6H5N2+HSO4–), Benzene diazonium chloride (C6H5N2+Cl–),etc. are some notable examples of the diazonium salt.
Diazonium salts are one of the most versatile combinations of organic and inorganic components. Its general way of representation is R−N2+X−. The R stands for an organic group, more often an aryl group while X stands for ion.
Generally, diazonium salts have Cl–, Br–, BF4−, as X. The name of these salts is based on the presence of diazonium group or the N2+group.
The naming of these salts is done by adding the suffix diazonium to the parent hydrocarbon from which they are derived and then it is followed by the anion X such as bromide.
The importance of these compounds is situated in their application and uses.
Diazonium Salts Preparation
The process of converting an organic compound, more commonly primary aromatic amines, into diazonium salts is called dissociation or diazotization.
It has been seen that under normal conditions, the diazonium group is highly unstable and therefore, it is not generally preserved, it is generally used just after it is prepared.
One of the most common methods of preparation of diazonium salt is by reacting aromatic amines with nitrous acid. The reaction of with nitrous acid with aniline results in the diazonium salt formation which is named as benzene diazonium chloride.
Nitrous acid is a highly poisonous gas and hence it is generally prepared during the reaction itself by reacting mineral acid with NaNO2.
Another important factor that determines the product formation during the preparation of these salts is temperature; most diazonium salts are stable below the temperature of 5o C.
It is, hence, necessary to keep the reaction parameters below 5oC or otherwise the diazonium group will decompose into nitrogen as soon as it is made.
The reaction of aniline with hydrochloric acid and NaNO2, the product which is formed is benzene diazonium chloride.
C6H5NH2+NaNO2+2HClC6H5N2+Cl–+NaCl+2H2O
The diazonium group finds application in many ways. From synthesis of various organic compounds to dyes and pigment industry, this combination of organic and inorganic components has been a blessing for the scientists in these respective industries.
Properties of Diazonium Salts
They are ionic in nature.
They are water-soluble.
Aryl diazonium salts are colourless crystalline solids.
Benzenediazonium chloride is soluble in water but it only reacts with water when it is warmed.
Benzenediazonium fluoroborate is not soluble in water. It is very stable at room temperature.
Importance of Diazonium Salts
They find application in the dye and pigment industries and are very useful in producing dyed fabrics.
Due to their property of breaking down near the ultraviolet light, they are used in document reproduction
They are useful in the synthesis of a large variety of organic compounds, especially aryl derivatives.
Direct halogenation is not a very suitable way for preparing aryl iodides and fluorides. Nucleophilic substitution of chlorine in chlorobenzene by a cyano group is not possible. However, diazonium salts can easily be used to produce cyanobenzene.
It is not possible to prepare substituted aromatic compounds by direct substitution in benzene. For these compounds, we use the exchange of the diazo group in diazonium salts.
They are used as in-between for introducing –OH ,–I,–Br,–F, –Cl, –NO2, and –CN groups into the aromatic ring.
Conclusion: –
Diazonium salts are very important in the industry, it is a very important part in dye and pigment industries and it is also used in manufacturing of large organic compounds.
