This document describes the synthesis of 7-hydroxy-4-methyl coumarin via the Pechmann reaction. The Pechmann reaction involves the condensation of resorcinol with ethyl acetoacetate in concentrated sulfuric acid. The reaction mechanism proceeds through the initial formation of a β-hydroxy ester intermediate, which then cyclizes and dehydrates to form the coumarin product. Following the described procedure yields 4.3g of a pale yellow solid product, which is 49% of the theoretical yield. Characterization by TLC shows the product has a different Rf value than the starting materials, indicating formation of 7-hydroxy-4-methyl coumarin.

1. MEDICINAL CHEMISTRY III PRACTICAL'S
EXPERIMENT NO.- 2
SYNTHESIS OF 7-HYDROXY- 4-METHLY
COUMARIN
Mrs. Pradnya Mane
Assistant Professor,
Sarojini College of Pharmacy,
Kolhapur.

2. Aim: To synthesize 7-hyroxy-4-methyl coumarin
Requirements:
Chemicals:
Conc. Sulphuric acid, resorcinol, ethyl acetoacetate, ice,
methanol(95%)
Apparatus:
beaker, measuring cylinder, buchner funnel, filter paper

3. Principle:
A general principal of coumarin involves the interaction of a
phenol with a ß- ketoester in presence of an acid condensing
agent (Pechmann reaction). Conc. Sulphuric acid is usually used
as the condensing agent for simple monohydric phenols and ß-
ketoesters, although phenol itself reacts better in the presence of
aluminium chloride. The mechanism of the reaction is thought
to involve the initial formation of a ß-hydroxy ester, which then
cyclises and dehydrates to yield the coumarin. Polyhydric
phenols, particularly here the two hydroxy groups are meta
oriented react with greater ease and sulphuric acid is used as
the condensing agent with careful temperature control to ensure
a good yield.

4. REACTION

5. MECHANISM OF REACTION

6. PROCEDURE
 In 100 ml conical flask put 5.5 gm of resorcinol
(0.05M ) and 6.4 ml of ethyl acetoacetate then
add 50 ml of H2SO4to conical flask.
 Heat a mixture on the water bath for 30 minutes.
 Cool the resulting solution and stir into crushed
ice 250 gm.
 Filter the product and wash with 100 ml H2O
then weight this product.
 Crystallization of the coumarin carried out by
methanol and then measure the product

7. CALCULATION
 Molecular formula of resorcinol = C6H6O2
 Molecular formula of 7-hydroxy-4-methyl
coumarin = C10H8O3
 Molecular weight of resorcinol = 110 g/mole
 Molecular weight of 7-hydroxy-4-methyl
coumarin = 176 g/mole

8.  Therotical yield:
110 g of resorcinol forms 176 g of 7-hydroxy-4-methyl
coumarin
Therefore, 5.5 g of resorcinol will form ….. (X) g of 7-
hydroxy-4-methyl coumarin
Therotical yield = 5.5 × 176/110
= 8.8 g
 Practical yield:
Practical yield:
Practical yield =…4.3….. g
(weight of product obtained after synthesis)

9. (Practical Yield)
% Practical Yield = ---------------------- × 100
( Therotical Yield)
= 4.3 / 8.8 × 100
= 49 %

10.  Result:
 Therotical yield = 8.8 gm
 Practical yield = 4.3 gm
 % practical yield = 49 %
 Melting point =188-189°C

11. CHARACTERIZATION
 The product was obtained in a pale-yellow color and odorless solid
resembling flake.
 TLC identification showed a new spot different from its precursors
in n-hexane: ethyl acetate (3:2 v/v) with Rf of resorcinol, ethyl
acetoacetate, and product were 0.52, 0.80, and 0.46, respectively
 Because the product had a different Rf value than the starting
product, the 7-hydroxy-4-methyl coumarin is obviously not still
resorcinol. Also, as the dots were fairly distinct, it seems to lead to
the conclusion that there is no evidence that there is presence of
the starting material in the reaction product.