ORGANIC cHEMISTRY - IV

Experiment 2

Aim of the Experiment:

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

Materials required:

Concentrated sulphuric acid , ethyl acetoacetate , Resorcinol

THEORY

Coumarin derivatives are prepared from Pechmann condensation of resorcinol and ethyl acetoacetate in presence of any acid. Coumarin derivatives are widely used as drugs, as fragrance ingredients and in cosmetic industries. In this condensation reaction concentrated sulphuric acid or poly phosphoric acid (PPA) is used

PROCEDURE

• Concentrated sulphuric acid(15 ml) taken in a 50 ml conical flask is cooled to 5 degree Celsius by external ice water cooling.

• Add 3.7g of powdered resorcinol to 4.5g (4.4ml) of ethyl acetoacetate in to a separate beaker. Stir the mixture until a complete solution is obtain.

• Now add this solution slowly to the sulphuric acid so that the temperature of the mixture does not rise above100 degree Celsius and continue stirring for 30 minutes.

• Pour the mixture into crushed ice (100g).

• When the coumarin separates, filter and dry.

• Recrystallise from ethanol.

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

• Density of ethyl acetoacetate = 1.012 g/cm3

OBSERVATION

Weight of 7- hydroxyl 4-methyl coumarin obtained =

Observed melting point =

CALCULATIONS

110 g of resorcinol = 176 g of 7-hydroxy 4 methyl coumarin 3.7 g of resorcinol

EQUATIONS

REACTION MECHANISM

CALCULATIONS

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

3.7 g of resorcinol =

RESULT

Weight of 7-hydroxy4-methyl coumarin =

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

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