ORGANIC cHEMISTRY - II

Experiment 4

Aim of the Experiment

Synthesis of 7- acetoxy -4-methyl coumarin from resorcinol via 7-hydroxy-4-methyl coumarin (pechmann condensation )

Materials required:

Resorcinol, ethyl acetoacetate , concentrated sulphuric acid, acetic anhydride

Procedure

PART 1

SYNTHESIS OF 7-HYDROXY-4-METHYL COUMARIN FROM RESORCINOL

• Take 3g of resorcinol (0.0273 moles ) and 3.6g of ethyl acetoacetate in a dry round bottom flask in 100 ml capacity, fitted with the water condenser and the guard tube .

• Add slowly 1 ml of concentrated sulphuric acid dropwise and heat it in the water bath for 2 hours . Pour the reaction mixture in 150 ml of ice water to separate the products .

• Break the lumps and filter , dry and recrystallize from aqueous ethanol around 70 percent

• Reported melting point – 184 degree Celsius – 185 degree Celsius

• Density of ethyl acetoacetate = 1.012 g/cm3

PART 2

PREPARATION OF 7- ACETOXY 4- METHYL COUMARIN FROM 7- HYDROXY 4- METHYL COUMARIN

• Take 2-3 g of 7- hydroxyl – 4 methyl coumarin in a dry round bottom flask fitted with the water condenser and guard tube.

• Add 5-6 ml of acetic anhydride and place the flask in water bath.

• Add 2-3 drops of concentrated sulphuric acid and shake well .

• Solid product will start to separate.

• Heat the content of flask on water bath for 20-30 minutes to cool the flask.

• Pour the reaction mixture in 150 ml of water .

• Filter the precipitated product and recrystallize from aqueous alcohol.

• Reported melting point = 151 degree Celsius

EQUATIONS(PART 1)

OBSERVATIONS PART 1

Weight of 7- hydroxyl 4-methyl coumarin obtained =

Observed melting point =

CALCULATIONS(PART 1 )

110 g of resorcinol = 176 g of 7-hydroxy 4 methyl coumarin

3 g of resorcinol =

OBSERVATIONS(PART 2)

Weight of 7-acetoxy-4 methyl coumarin =

Observed melting point =

CALCULATIONS(PART 2 )

176 g of 7-hydroxy 4 – methyl coumarin = 218 g of 7-acetoxy 4- methyl coumarin

RESULT

PART 1

Weight of 7-hydroxy4-methyl coumarin =

Percent yield of 7-hydroxy-4-methyl coumarin =

Melting point of 7-hydroxy-4-methyl coumarin =

PART 2

Weight of 7-acetoxy-4-methyl-coumarin =

Percent yield of 7-acetoxy-4-methyl-coumarin=

Melting point of 7-acetoxy-4-methyl-coumarin=