Chemistry XXI
Lab Session 12
How do we synthesize
new substances?
(Two-Week Experiment)
The End is Near(ing)
9
10
11
12
13
VTs Day
Make up
19
20
Chemistry XXI
VTs Day
No classes
16
CHEM 151
Exam 3
17
23
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24
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30
1
December
Lab Finals
Week
Lab Finals
Week
7
CHEM 151
Exam 4
18
25
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26
27
Thanksgiving No classes
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2
Lab Finals
Week
8
4
Lab Finals
Week
9
Last Day
3
10
DEAD DAY
No Classes
11
Finals
Begin
What have we done?
Until now we have been focused on
Chemical Analysis.
Central Goals and Questions
Chemistry XXI
Detection:
Does the sample contain
substance X?
Identification:
What is the identity of the
substance in this sample?
Separation:
How can the substances
present in the sample be
separated?
Quantitation:
How much of substance X
is in the sample?
Where are we going?
Analysis
What is this?
Synthesis
How do I make it?
Chemistry XXI
Transformation
How do I change it?
Modeling
How do I explain it?
We will now start to explore the ideas and
techniques used to “synthesize” new substances.
Chemistry XXI
Chemical Synthesis
Chemical synthesis
has given us,
among other things,
many of the
medicinal drugs
that have
dramatically
increased life
quality and span in
the past 100 years.
Aspirin - 1880s
Heroin – 1890’s
Sulfa drugs – 1940’s
Statins – 1980’s
Viagra – Y2K
Personalized drugs –
Soon (perhaps)
Your Challenge
Imagine that you work for a drug company
interested in testing a new procedure to
synthesize aspirin.
Chemistry XXI
You have been asked to evaluate whether the
procedure is feasible and marketable.
What do you have to do to complete your task?
Initial Ideas
Discuss in your groups what types of tests you
have to do and what type of information you need
to evaluate the feasibility and marketability of
this procedure.
C7H6O3
Chemistry XXI
Salicylic
acid
+
C4H6O3 
Acetic
anhydride
C9H8O4 + C2H4O2
Acetyl
salicylic
acid
(Aspirin)
Acetic
acid
 Cost of Ingredients and manufacture;
 Safety issues;
Reaction yield.
Costs
We need to find out the cost of the reactants.
C7H6O3
+
Chemistry XXI
Salicylic
acid
Chemical
C4H6O3 
Acetic
anhydride
Cost
C9H8O4 + C2H4O2
Acetyl
salycilic
acid
(Aspirin)
Amount
http://www.fishersci.com/
Acetic
acid
Other Costs
Make a list of other costs that would have to be
determined. Make an estimate for each.
 People to perform the reaction;
Chemistry XXI
 Packaging;
 Marketing;
 Management.
Safety
Chemistry XXI
While we’re looking up chemicals,
let’s also look at the best source of
information regarding the dangers of
chemicals –
The Material Safety Data Sheet.
http://www.fishersci.com/
Safety
Chemistry XXI
As you can see, the
reagents used in this
reaction have the potential
to cause chemical burns
and possibly allergic
reactions.
To protect yourself from
inadvertent contact with
these chemicals you must
wear gloves while
performing the experiment.
Reaction Analysis
Acid
Catalyst
Chemistry XXI
It is proposed to use 2.0 g of C7H6O3 with
9 mL of C4H6O3 (r = 1.082 g/mL ) to do the reaction.
The Acetic anhydride is added in excess. Thus, the
maximum amount of aspirin that can be synthesized
is determined by the initial amount of Salicylic acid.
How many moles of C7H6O3 will you use?
Theoretical Yield
Chemistry XXI
Acid
Catalyst
Calculate the maximum amount of Aspirin, in
grams, that you will be able to synthesize?
This amount is called the
“Theoretical Yield.”
Why should you expect a lower yield than this?
Actual or Percent Yield
How are you going to
calculate the actual yield of
your reaction?
Chemistry XXI
What measurements and
calculation do you need to
make?
[Actual Mass of Product]
Percent Yield 
x 100
[Theoretic al Mass of Product]
Your Challenge
Following the procedure given in your lab
manual, manufacture some aspirin.
Available resources:
You have 90
minutes
Chemistry XXI
 Salicylic acid and acetic
anhydride.
 Balances (TC 4).
 Volumetric glassware.
Once you finish,
report your percent
yield on the board.
BUT, before you go…….
Safety
Precautions
The acetic anhydride is
destroyed by water.
All glassware must be dry.
 Step 3 - The cotton plug is to
keep water vapor out of the
reaction flask.
Chemistry XXI
 Step 6 – The reaction of acetic
anhydride with water can be
violent.
 Step 6 - When transferring the
product keep the amount of
water added to a minimum.
Claims and Evidence
Based on the results of your experiments,
present your major claims (percent yield)
and the evidence that you have to
support the answer to the challenge.
 Are their claims clear?
Chemistry XXI
 Is the evidence reliable?
 Is the evidence appropriate to support the
claims?
 How do you explain the results?
Reflections
What’s next?
Can we put our crude aspirin into
tablets?
Chemistry XXI
What do we need to do now?
We need to purify our product
How?
Chemistry XXI
Recrystallization
In your group, create an
outline of the various things
you will need to do to
successfully recrystallize
your aspirin.
Your Next Challenge
Recrystallize your aspirin product.
Available resources:
 Ethanol
You have
60 minutes
Chemistry XXI
 Glassware
 Ice bath
 Hot plate
Once you finish, report
your new percent yield
on the board.
Claims and Evidence
Based on the results of your experiments,
present your major claims (percent yield)
and the evidence that you have to
support the answer to the challenge.
 Are their claims clear?
Chemistry XXI
 Is the evidence reliable?
 Is the evidence appropriate to support the
claims?
 How do you explain the results?
Final Reflections
 What did you learn from doing your
experiment?
 How would you improve what you did?
Chemistry XXI
 How have your ideas changed as a result
of this lab?
 What do you not completely understand?
 What new questions do you have?
Next Week
Can we put our recrystallized aspirin
into tablets?
What kind of chemical analysis remains
to be done?
Chemistry XXI
How are we going to achieve it?
 Melting point
 TLC
 Titration
No Report
due
Next Week