Synthesis of Phenothiazine

1.   Objective

To synthesize Phenothiazine from Diphenyl amine and calculate its practical yield and percentage yield.

2.   References

Furniss, B. S., Hannaford, A. J., Rogers, V., Smith, P. W. G., & Tatchell, A. R. (1978). Vogel’s Textbook of Practical Organic Chemistry, Including Qualitative Organic Analysis. ELBS.

3.   Materials required

Diphenyl amine, Sulphur, Iodine, Ethanol, Activated charcoal, RBF, Reflux condenser, Oil bath, porcelain dish, Heating mantle, Thermometer, Magnetic stirrer.

4.   Theory

Diphenyl amine when treated with sulphur undergoes fusion reaction in the presence of iodine to give phenothiazine, a tricyclic compound with rapid evolution of hydrogen sulphide.

phenothiazine synthesis

5.   Procedure

In a round bottom flask fitted with reflux condenser, place 16.8 g of diphenylamine, 6.4 g of sulphur and 300 mg of iodine. Reflux the mixture on an oil bath at 190-200°C for 30-40 minutes with the rapid evolution of hydrogen sulphide. By lowering the temperature, a few degrees the reaction can be slackened. Cool and grind the residue mass, in which 5 ml of ethanol and pinch of animal charcoal is added and heat it until solid mass dissolves. Filter the solution while hot and cool in ice bath. The residue consists of almost pure phenothiazine. It can be recrystallised from alcohol. The melting point of the yellow crystals of phenothiazine is 184-185°C.

6.   Observation

Melting point –

7.   Calculation

Theoretical Yield –

Practical Yield –

Percentage yield =

8.   Results

The Phenothiazine was synthesized from Diphenyl amine. The practical yield and percentage yield was found to be …… and ……. respectively. The melting point was found to be ….. °C.

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