Aim: Preparation of 7-acetoxy 4-methyl coumarin from resorcinol

Requirements:

  • Resorcinol = 5.0 g.
  • Ethyl acetoacetate = 5.9 mL
  • sulphuric acid = 22.0 mL + 5.0 mL
  • Acetic anhydride = 10.0 mL

Procedure:

Step 1: 7-hydroxy 4-methyl coumarin from resorcinol

            To a solution of 5.0 g of resorcinol in 5.9 mL of ethyl acetoacetate contained in a 150 mL conical flask add 22.0 mL sulphuric acid or polyphosphoric acid stir the mixture with thermometer and heat on water bath 75-80 °C for 20 minutes pour in to excess of ice water collect the pale-yellow solid by suction filtration wash with cold water and dry at 60 °C. recrystallize from ethanol m.p. = 185 °C.

Step 2: 7-acetoxy 4-methyl coumarin from 7-hydroxy 4-methyl coumarin

A mixture of 7-hydroxy 4-methyl coumarin acetic anhydride and concentrated sulphuric acid is shaken in a conical flask heated on a water bath at 60-70 °C for 1 hr. with occasional stirring. The reaction mixture is cooled dilute with water and filter the product dry it. Recrystallized from ethanol m.p. = 150-153 °C.

Results:

Step 1.

  • Theoretical Yield: ______________g.
  • Practical Yield: ________________g.
  • % Yield of the product: _____________%.
  • M.P of 7-hydroxy 4-methyl coumarin (recrystallize): ___________°C

Step 2.

  • Theoretical Yield: ______________g.
  • Practical Yield: ________________g.
  • % Yield of the product: _____________%.
  • M.P of 7-acetoxy 4-methyl coumarin (recrystallize): ___________°C

Chemical Reaction:

Mechanism:

Calculation:

Step 1.

  • Theoretical Yield

Resorcinol: C6H5O2 (110.0 g.) 7-hydroxy 4-methyl coumarin: C10H8O3 (174.0 g.)

From Chemical Reaction

110.0 g. Resorcinol               =                      174.0 g. 7-hydroxy 4-methyl coumarin

∴ 5.0 g. Resorcinol                =                      (?) g. 7-hydroxy 4-methyl coumarin

                        = \frac{5.0 \times 174.0}{110.0}     

                        = 7.90 g.

  • Practical Yield:

Actual weight of the dried product = ________________g.

  • % of Yield =\frac{\text { Practical Yield } \times 100}{\text { Theoretical Yield }}

                             = _______________%

Step 2.

  • Theoretical Yield

7-hydroxy 4-methyl coumarin: C10H8O3 (174.0 g.)

7-acetoxy 4-methyl coumarin: C12H10O4 (218.0 g.)

From Chemical Reaction

174.0 g. 7-hydroxy 4-methyl coumarin     =          218.0 g. 7-acetoxy 4-methyl coumarin

∴ 5.0 g. 7-hydroxy 4-methyl coumarin     =          (?) g. 7-acetoxy 4-methyl coumarin

                        =\frac{5.0 \times 218.0}{174.0}        

                        = 6.26 g.

  • Practical Yield:

Actual weight of the dried product = ________________g.

  • % of Yield =\frac{\text { Practical Yield } \times 100}{\text { Theoretical Yield }}

                             = _______________%