Question

Which of the following is not a Karl Fischer reagent

• A. Iodine
• B. Pyridine
• C. Pyrimidine
• D. Sulphur dioxide

Hint:

Remember: Karl Fischer reagent = Iodine + SO$_2$ + Base (e.g., Pyridine) + Alcohol (e.g., Methanol)

Answer 1

The Correct Option is C

Karl Fischer titration is a widely used analytical technique for the determination of water content in pharmaceutical substances. The classical Karl Fischer reagent consists of: - Iodine (I$_2$): Acts as an oxidizing agent.
- Sulphur dioxide (SO$_2$): Serves as a reducing agent.
- Pyridine: Functions as a base to neutralize the acid formed during the reaction and to stabilize the intermediate complex.
- Methanol or other alcohols are used as solvents.
Pyrimidine, on the other hand, is a heterocyclic compound and is not a component of the Karl Fischer reagent. It is not involved in the reaction mechanism or stabilization of the intermediates in water determination, and hence, is not part of the reagent composition.