SYNTHESIS OF 1,3-PYRAZOLE (ANTIPYRINE)#

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Aim: To prepare and submit Antipyrine from given quantity of Ethyl acetoacetate.
Apparatus: Round bottomed flask, Condenser, Water bath, Beaker, Funnel, Glass rod
Chemicals: Ethyl acetoacetate, Phenyl hydrazine, Diethyl ether.
Principle: The reaction principle involves condensation between phenyl hydrazine and ethyl aceto acetate at 1000C for 2 hours followed by cyclization and dehydration. Antipyrine reduces pain and fever in migraines and chronic rheumatism. Antipyrine is obtained upon methylation of 3-Methyl-1-phenyl-5-pyrazolone with dimethylsulphate in alkaline medium.

Reaction:
Procedure: 
Step-1 
A mixture of ethyl aceto acetate (4.9ml) and phenyl hydrazine (3.65ml) was heated in a 100 ml RBF for 2hrs with continuous stirring. The reaction mixture was allowed to cool and 20 ml of diethyl ether was added to it with continuous stirring. The separated product was washed with water and recrystallized using ethanol. Dry and collect the product.
 Step-2 
In a 250 ml three necked RBF fitted with a dropping funnel, a sealed stirrer unit and a double surfaced condenser, add 1 g of NaOH in small volume of water and also add 4.35 g of  3-Methyl-1-phenyl-5-pyrazolone in methanol. Warm the mixture in water bath and add 3.6 g of dimethyl sulphate. Reflux for 1 hour. Allow to cool. Pour in crushed ice-water mixture. Filter the product. Dry and recrystallize with hot water and decolorizing charcoal.
Precautions: Both vapour and liquid dimethyl sulphate are highly poisonous and should only be used in fume cupboard. Heating should be continued till a test portion solidifies.

Calculation:
 Molecular weight of Ethylacetoacetate = 130.14gm
Molecular weight of antipyrine  = 188.225gm/mol
130.14gm of ethylacetoacetate gives                        188.22gm of antipyrine            
4.99g (4.9ml)of ethylacetoacetate                 X g  antipyrine
X=4.99*188.225/130.14=7.21gm


Theoretical yield =7.21g
Practical yield=----------------- g
Percentage yield = practical yield/ theoretical yieldx100=------------------------------%w/w
Report:

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