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A Practical Note Book
on
Medicinal Chemistry-III Lab
Course code: BPM00414
Submitted to:
Mr. Muhammad Rakib Al-Mamun
Senior Lecturer
Department of Pharmacy
Manarat International university
Submitted by:
Md.Saiful Islam
ID: 0915BPM00485
Department of pharmacy
Manarat International University
Submission date:
23.02.2013
signature:
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Index
Experiment No
01
Name of the Experiment
Synthesis of Methyl Salicylate
(Oil of wintergreen)
Page No
3-5
Date
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Experiment No: 01
Name of the Experiment: Synthesis of Methyl Salicylate (Oil of wintergreen).
Principle: The reaction of carboxylic acid and alcohol produces an ester and water.
The reaction is catalyzed with acid. Easter often have a fruity taste or odor. Here
methyl Salicylate, prepared using methanol as the alcohol, will give smell like
wintergreen.
Reaction:
+ CH3OH
Salicylic Acid
Methanol
+ H2 O
Methyl Salicylate
Reagents:
i.
ii.
iii.
iv.
v.
vi.
Dry salicylic acid.
Pure methanol.
Concentrated sulfuric acid.
Distilled water.
5% sodium bicarbonate.
Anhydrous calcium chloride.
Apparatus:
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
Round bottom flask.
Reflux condenser.
Separating funnel.
Stand.
Ice bath.
Measuring cylinder.
Electric balance.
Distillation apparatus.
Procedure:
i.
ii.
iii.
iv.
The reflux apparatus is set using a 250ml round bottom flask.
0.05mole i.e. 6.9gm of salicylic acid is taken in the round bottom flask and
30ml of methanol is added.
8ml of concentrated H2SO4 is added into it gently.
The flask is swirled gently to thoroughly mix the reactants.
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v.
vi.
vii.
viii.
ix.
x.
xi.
xii.
xiii.
xiv.
A reflux condenser is attached to the round bottomed flask and using a
heating mantel, the mixture is refluxed gently for two hours.
The reaction flask is cooled by immersing it in ice water bath.
The content of the flask is poured into 100ml of cold distilled water
contained in a 400ml beaker.
The reaction mixture is placed in a separating funnel, to determine the
aqueous layer 50% sodium bicarbonate solution is added.
The mixture is placed washed gently swirling. The aqueous layer is
discarded.
The organic layer is poured into an Erlenmeyer flask and dried with
anhydrous calcium chloride.
The ester is decanted and the mass of the product is recorded.
The ester is combined with other groups for distillation into a distillation
flask by filtering through a funnel with a small cotton plug. Methyl
Salicylate boils at 2220c. This is very high temperature to do a distillation;
in order to do this a low pressure distillation is set up by attaching a water
aspirator to the place on the apparatus.
The fraction between 110-1150c is collected in a separate flask.
Pure oil of wintergreen is obtained.
Calculation:
Molecular weight of salicylic acid = 138gm
Molecular weight of methyl Salicylate = 152 gm.
138gm of salicylic acids yields =152 gm of methyl Salicylate
6.9gm of salicylic acids yields = 152 ×
6.9
gm of methyl Salicylate
138
= 7.6 gm of methyl Salicylate.
From the experiment, we get 6.81 gm of methyl Salicylate from 6.9 gm
salicylic acid.
Percentage of yield product =
=
Practical Value
× 100
Theoritica l Value
6.81
× 100
7 .6
= 89.61%
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Result: Percentage of yielded methyl Salicylate is 89.61.
Precautions:
i.
ii.
iii.
iv.
v.
All of the apparatus should be handled carefully.
All of the chemicals should be handled carefully.
All of the measurement should be done carefully.
Product should not be adhered at the side of the flask.
Boiling stones should be used.