What is Diazonium Salt?
Diazonium salt is also known as the diazonium compound. This word is derived from ‘di,’ which means two, ‘azo’ that is used to indicate nitrogen, and ‘ium,’ which is used to imply that these compounds are cationic.
This means that whenever someone asks you the question what is diazonium salt, then you can reply that diazonium salts are a class of organic compounds that have a general formula of R-N2+X-. In this general formula, X is an organic or inorganic anion, like Cl-, Br-, and BF4- while R is an alkyl or aryl group.
From this description, you must also be able to deduce that diazonium salts often have two nitrogen atoms, with one of those atoms being charged. Some examples of diazonium compounds include benzene diazonium chloride (C6H5N2+Cl-) and benzene diazonium hydrogen sulfate (C6H5N2+HSO4-). Both of these compounds also fall under the category of the benzene diazonium salt.
It is important for students to remember that diazonium salts are one of the most versatile combinations of organic and inorganic compounds. Because of this, the diazonium salt formula can also be repressed by R-N+2X- in a general manner. In this representation, R is an organic group, which is usually an aryl group, and X represents an ion.
Diazonium salts are one of the most versatile combinations of organic and inorganic components. Its general way of representation is R−N+2X−. The R is an organic group, generally an aryl group, while X represents ion.
Also, in most cases, diazonium salts have Cl-, Br-, and BF-4 as X. This must also give a general idea as to the most common diazonium salt formula that can come in exams. The name of the benzene diazonium salt is also based on the presence of the N+2 group.
According to the diazonium salt Class 12 chapter, the naming of these salts can be done by adding the suffix diazonium to the parent hydrocarbon from which the compound is derived. After that, the name is followed by the anion X like chloride and bromide. These compounds are very important in terms of their application and use in the general world.
Preparation of Diazonium Salt
In the diazonium salt Class 12 chapter, a large section of the chapter is devoted to the preparation of diazonium salt. This goes to show the importance of learning diazonium salt synthesis. In this section, you can learn just what the process of diazonium salt synthesis entails.
The first thing that one needs to learn about the synthesis of diazonium salts is the definition. According to experts, the process of converting an organic compound like primary aromatic amines into some sort of diazonium salt is called diazotization or dissociation.
It has also been observed that the diazonium group as a whole is very unstable under normal conditions. This means that it is not usually stored but is instead used right after its preparation.
And one of the most common methods that one can use for this preparation is by reacting nitrous acid with aromatic amines. This reaction of aromatic amine or aniline with nitrous acid will result in the formation of benzene diazonium chloride. This compound will have a diazonium salt structure.
Further, it is important to note that nitrous acid is a very toxic gas. This is why this gas must be prepared during the reaction itself. This can be done by reacting NaNO2 with a mineral acid. Apart from all these considerations, another important factor that one should keep in mind while preparing diazonium compounds is temperature.
Most diazonium salts are stable below the temperature of 50C. Hence, it is vital to keep the entire reaction below 50C. If these conditions are not met, then the diazonium group will completely decompose to give N2 as soon as it is formed.
To further get a clearer idea about the formation of diazonium compounds, let's look at the reaction of aniline with NaNO2 and hydrochloric acid.
C6H5NH2 + NaNO2 + 2HCL -----> (Temperature 0 - 50 C) C6H5N+ - Cl + NaCl + 2H20
In this reaction, the final product is benzene diazonium chloride. There are many synthetic uses of aryl diazonium salts. We shall be looking at what those uses are soon.
Properties of Diazonium Salt
Let’s now move on to discuss some properties of the diazonium salt. A list has been prepared of those properties, and that list is mentioned below.
Diazonium salts are ionic
These salts are soluble in water
Aryl diazonium salts are also colourless crystalline solids
Benzenediazonium chloride is soluble in water. But it will react with water when the temperature is raised
Benzenediazonium fluoroborate is not soluble in water. It is also quite stable at room temperature
These are some of the most important properties of diazonium salts.
Uses of Diazonium Salt
Have you ever wondered about the uses of diazonium salt? If yes, then today is your lucky day, as in this section, we are going to look at some of the most important uses of diazonium salts. We will also discuss synthetic uses of aryl diazonium salts.
According to various sources, the first use of diazonium salts was to produce water-fast dyed fabrics. This was done by immersing the fabric in an aqueous solution of the diazonium compound. After that, the item was immersed in a solution of the coupler. The coupler is an electron-rich ring that goes under electrophilic substitution.
Most other applications of diazonium compounds are also related to the dye and pigment industry. Other uses of diazonium compounds include using these compounds as standard reagents for the synthesis of different organic compounds like aryl derivatives.
Diazonium salts are also very light sensitive. These compounds break down under violet light or UV light. Because of this property, these compounds are used in document reproduction. In this process, the film or paper is coated with a diazonium salt.
After the initial contact exposure under light, the residual diazo is converted to a stable azo dye. This is done with the help of a coupler and ac acid to inhibit coupling. The acid is used after the exposure when the image is developed by a vapour mixture of ammonia and water. This forces coupling.
Fun Facts about Diazonium Salt
Did you know that direct halogenations is not a suitable method for preparing fluorides and aryl iodides? Because of this, the nucleophilic substitution of chlorine in chlorobenzene by a cyano group is not possible. But diazonium salts can easily produce cyanobenzene.
It is also not possible to prepare substituted aromatic compounds with direct substitution in benzene. Hence, for these compounds, the replacement of the diazo group in diazonium salts is done.
FAQs on Diazonium Salts Application
1. Can you define Diazonium salts?
Answer: Diazonium salts can be defined as a group of organic compounds that share one common R-N+2X- group of functions. In this formula, R is an organic group like alkyl or aryl. Further, azo compounds can be formed by carrying out a reaction with other aromatic compounds by diazonium salts.
2. How can one form Diazonium salts?
Answer: Diazonium salts are produced in the presence of hydrochloric acid. These salts are produced by taking an aryl or alkyl primary amine and adding that with sodium nitrite. An example that involves diazonium salts is the Sandmeyer reaction. This reaction includes the synthesis of an aryl chloride through the action of copper (I) chloride.
3. Why are Diazonium salts important?
Answer: Diazonium salts are used as standard reagents in the synthesis of organic compounds like aryl derivatives. These salts are sensitive to light and will break down under UV light. Due to this, these salts are used in the copying of paper. In this process, a diazonium salt is used to paint on paper or film.
