CSUS - CH6B
Synthesize of Aspirin
Instructor: J.T.,
P: 1
The theoretical yield of a reaction:
The amount of product that would be formed if the reaction went to completion.
A
+
→
B
C
1 mol
1 mol
n gram
?
(if it is balanced!)
You can convert "n, gram" to mol or moles to grams to have same units, using the relationship:
(
mole =
mass
MW
)
Next find the % of yield as:
% Yield =
mass of actual yied
× 100
mass of theoretical yield
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(1)
Physical properties:
Can be observed or measured without
changing the composition of matter.
For instance: Melting point.
(2)
The melting point of a solid is the temperature at which it changes state from solid to
liquid.
(3)
Application: melting point (m.P.) provided crucial information on the purity and identity
of solid organic compounds.
(4)
Impurities lower the melting point.
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The active extract of the bark, called salicin, after the Latin name for the White willow
(Salix Alba), Salicylic acid
CSUS - CH6B
Notes:
Synthesize of Aspirin
Instructor: J.T.,
P: 2
Use Phosphoric acid (H3PO4) and Heat.
The presence of water can lead to hydrolysis of the aspirin. Thus, an anhydrous
(“without water”) reagent could lead to better yields of product. This reagent is
acetic anhydride.
Salicylic acid + Acetic anhydride → Acetylsalicylic acid (Aspirin) + Acetic Acid
M.W.
m.p. C°
Salicylic acid
138.12
159
Acetic Anhydride
102.09
140
Aspirin
180.15
128 ~ 137
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(1)
In chemistry, recrystallization is a procedure for purifying
compounds.
(2)
The principle behind recrystallization is that the amount of solute that can be
dissolved by a solvent increases with temperature. (This is how rock candy is
made.)
(3)
The recrystallization process:
(a)
(b)
(c)
Dissolving the solute in the (right) solvent.
Collecting the solute crystals by vacuum filtration.
Drying the resulting crystal.
A Buchner funnel in a filter flask, with rubber tubing connected to an aspirator.
CSUS - CH6B
Synthesize of Aspirin
Note 1:
Acetyl Chloride:
Instructor: J.T.,
P: 3
O
H3C
C
Cl
Note 2:
Many organic acids are insoluble in water.
Example:
Benzoic acid: C6H5COOH
Low solubility in water: 0.29 g/100 mL (20 C°)
An "insoluble organic acid" will dissolve when the base neutralizes the acid.
C6H5COOH(s) + NaOH (aq) → C6H5COO-(aq) + Na+ (aq) + H2O (l)
Formation of salt: Sodium benzoate, a soluble compound in water.
Note 3:
An analgesic (a-nəl - ˈjē-zik), (colloquially known as a painkiller) is any member of the
diverse group of drugs used to relieve pain.
Note 3:
Antipyretics (an-tī -pī-ˈre-tik) are drugs that prevent or reduce fever by lowering the body
temperature from a raised state. However, they will not affect the normal body
temperature if one does not have fever.