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Diazonium Salt
The Diazonium salts are an organic group that share the same functional group R−N2+X− where R denotes some organic residue (such as an aryl or alkyl group), and the X is an organic or inorganic anion (a halogen, for example). A key intermediate in the organic synthesis of azo dyes is diazonium salts containing an aryl group. An anion name like chloride or hydrogen sulphate is prefixed with the suffix “diazonium” before the parent hydrocarbon name. An N2+ ion known as diazonium is commonly used to refer to the entire diazonium family. It’s known as benzene-diazonium chloride, for example, C6H5N2+Cl–. Diazonium salts are colourless crystals that dissolve easily in water. When they are in a dry state, they decompose very quickly.
Between azo dyes and diazonium salts, there is a transition phase (or compounds are known to be popular colouring agents). Ionic salts, in which chloride molecules replace the nitrogen atom, are known as salts due to the presence of a second nitrogen atom (diazo). Diazonium salts can be made in a relatively straightforward manner. The following are the procedures to be followed for a diazonium salt reaction.
Step I: Start with an alkyl or a primary aryl amine as your starting point.
Step II: Nitrogen triple bonds are formed, and water is lost when sodium nitrite and hydrochloric acid come into contact.
Step III: Below or at room temperature, the gentle reaction process can take place.
Chemical Reactions of Diazonium Salts
Since the construction blocks for other organic reactions can be synthesised from diazonium salt reactions, so it is necessary to study these reactions. These reactions can be classified as either Sandmeyer reactions or as a result of the use of other mechanisms. Diazonium Salt reactions are as follows:
Type I: Sandmeyer Reaction
An aryl diazonium salt can be converted into an aryl halide by using the Sandmeyer reaction, a radical-nucleophilic aromatic substitution. The Sandmeyer reaction is responsible for many of Benzene’s transformations, including Benzene and halogenation. The nucleophile can be cyanide, thiols, or halide anions, and this method makes it easy to substitute an aromatic amine into copper(I) salts.
Starting with diazonium salts and copper compounds like copper (I) chloride is a good place to start in these reactions. It is known as the Sandmeyer reaction, when copper (I) chloride reacts with aryl chloride to form copper chloride. There’s a copper (I) chloride reagent discovered in 1884 by Swiss chemist Traugott Sandmeyer that causes a rapid loss of nitrogen from diazonium salts.
The reaction is made up of the following steps:
- To make an arylamine, you must start with its nitro compound, where the benzene ring is deactivated, and electrophilic replacements take place in multiple meta locations.
- Electrophilic substitution occurs at ortho and para locations when the amine’s nitro group is reduced, activating the aromatic ring.
- Aryl amines are converted into diazonium ions, which can then be used in the next-in-line reactions.
Some examples are as follows:
The aryl diazonium salts are converted to aryl chlorides, bromides, and cyanides using CuCl, CuBr, and CuCN.
Type II – Other Reactions
Schiemann Reaction
Aryl fluorides can be formed when the diazonium salt (X;) ion is substituted with the tetrafluoroborate (BF4– ) ion. With heat exposure, stable diazonium tetrafluoroborate salts may become nucleophiles and lose their nitrogen; to yield aryl fluoride and N2 as byproducts, as well as BF3 and BF4 ions. The chemical equation for the Schiemann reaction is shown in the figure below.
Phenol Synthesis
Aryl diazonium salt (aryl diazonium salt) is heated with water and acid to form hydroxyl groups (OH). In pharmaceuticals and drug development, these phenols are essential building blocks. The underlying chemistry is as follows:
Aryl Iodide
They also react with potassium iodide to produce aryl diazonium salts. The following is the chemical reaction that occurs during the process:
