Learn the principle, theory, types, and applications of diazotization titration, which involves the conversion of an aromatic amine into diazonium compounds.
Titration is a method of chemical qualitative analysis used to determine the unknown concentration of an analyte. It is also known as titrimetry and volumetric analysis, in which an endpoint is determined by adding a known concentration of titrant to an unknown amount of analyte. Titration can be classified based on its procedures and goals, such as acid-base titration, precipitation titration, complexometric titration, and redox titration.
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What is diazotization titration?
In pharmaceutical analysis, diazotization titration is a type of titration that involves the conversion of the primary aromatic amines into particular diazonium compounds. The reaction mechanism for diazotization titration was first discovered in 1853 by Peter Griessin.
According to his reactions, a diazonium compound or salt will be formed when the primary aromatic group reacts with sodium nitrite (NaNO2). Furthermore, the medium of this reaction is acidic.
Principle of diazotization titrations:
The basic principle behind diazotization titration is that, in the presence of an acid, the given sample of a primary aromatic amine will react with sodium nitrite (NaNO2) to yield a diazonium salt (for example, hydrochloric acid).
The chemical reaction of this process is as follows:
R-NH2+ NaNO2+ HCl→ R-N+≡ N-Cl–+ NaCl + H2O
Theory:
You will use sodium nitrite for the direct diazotization method in an acidic medium. it will release HNO2, and by measuring the volume of NaNO2 in the solution, we can easily analyze the number of primary amine groups that have free -NH2 groups.
The chemical reaction of this process is as follows:
NaNO2 + HCl →HONO + NaCl
ArNH2 + HONO + HCl →ArN2Cl + 2H2O
Using the starch paper test or an indicator, you can find the excess NaNO2 that is still present in the solution. Excess sodium nitrite (NaNO2) indicates that the reaction has reached its endpoint. The starch and I2 that are released at the end will react to produce a blue color. It is significant to note that it will only occur when an inorganic acid is present. Therefore, the following chemical reaction occurs to test it with starch iodide paper or solution:
KI + HCl →HI+ KCl
2HI +2HONO→ I2 +2NO +2H2O (excess)
I2 + Solution of paste of starch→ blue color (endpoint)
Types of diazotization titrations:
There are three different types of diazotization titration: direct method, indirect method, and other methods.
Direct Method:
The process consists of treating an amino group with an acidic solution, to yield the diazonium salts of the diazonium compounds. This solution will be stored in ice water to keep the temperature between 0 to 5°C. Then, titrate it with sodium nitrate and observe the endpoint.
Indirect method:
The indirect method of titration applies to insoluble diazonium salts. In this technique, you will need to add the excess nitrous acid into the sample titration solution. You need to titrate it against some other since it is an insoluble diazonium salt.
Other methods:
The other method consists of conversion into diazo oxides, which are typically more stable than diazo compounds.
Factors affecting diazotization titrations:
The following are some of the factors that affect diazotization titration:
- The acid concentration used in titration
- Time taken by the reaction
- The efficiency of the attached diazotized group (rapid or slow)
- The pH of sodium nitrite
- Reaction temperature
Application of diazotization titrations:
- The analysis of sulfonamides is the basic application of diazotization titration in pharmaceuticals.
- It is used to determine the primary aromatic amine compound.
- Diazotization titration is also used to determine the chlorophenol, alpha drug, procaine, etc.
- It is commonly used in the dye and pigment industries.
Commonly asked questions on diazotization titrations are as follows.
What are the conditions required for diazotization titrations?
Maintaining the temperature of the reaction and rate of titration are the conditions required for diazotization titrations.
What indicator is used in diazotization titration?
Starch iodide paper is used as an indicator to indicate the endpoint of a reaction in diazotization titrations.
Why is HCl used in diazotization?
The diazotization reaction is conducted in the presence of excess HCl to avoid azo coupling.
What is the other name for diazotization titration?
Diazotization titration is also known as nitrite titration which is used in the analysis of aromatic compounds containing an amino group in the molecules.
What are the examples of slow and fast diazotized groups?
Nitrogen oxide, carboxylic groups, and sulpha, are examples of slow diazotized groups, and anilide, toluidine, and aminophenol are examples of fast diazotized groups.
Keaywords:
Applications, examples, principle, advantages and disadvantages
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