(CHE 276) Organic Chemistry Laboratory Lab References Totah rev. 8/2011 5 The Laboratory Notebook Your notebook will serve as a permanent record of your experimental work. It will contain the information you need to complete your work efficiently and safely, and you will use the information contained in your notebook to write laboratory reports explaining your results. For these reasons, it is important that your notebook be complete and accurate. As a general rule, a good notebook is one from which someone else can repeat your experimental work in the same way that you have done it. I. General Guidelines: 1. Your notebook must be bound, the pages numbered, and have a carbon copy. 2. Write your name, the course name, and section # on the cover or front page. 3. Always use permanent ink, not pencil. 4. Write it down NOW. Your notebook is a log of what you do as you do it. 5. Use complete sentences. 6. Write everything in your notebook. Weights, temperatures, everything! When recording experimental data, always include units. 7. Do not erase! If you make an error, draw a single line through it, and continue. The original statement should still be legible. 8. Never remove original pages from your notebook. You may remove carbon copies. 9. Date every page as you use it. 10. Write legibly! If your notebook is illegible it will not be graded. II. The Notebook: Each experiment recorded in your notebook should contain the sections outlined below. A carbon copy of your notebook pages will be collected at the end of each laboratory period and will graded as a part of your lab report. Late notebook pages will not be accepted. Sections A - E must be completed before you begin the experiment. This is the prelab. Your TA will verify that this section is complete. You will not be allowed to proceed with the experiment if you have not completed the prelab. Section F, the Experimental, is recorded as you proceed each day.  Prelab: Completed before you arrive. A. Title: Give the experiment an accurate, descriptive title. B. Purpose: Discuss the general purpose of the experiment in two or three sentences. If the experiment is a synthesis (as opposed to a technique), write the chemical equation, including reagents and expected product(s). For multistep syntheses, write one equation for each transformation, including the preparation of reagents. (CHE 276) Organic Chemistry Laboratory The Laboratory Notebook 6 Totah rev. 8/2011 C. References: Cite the reference upon which your experimental procedure is based. In most cases this will be your laboratory manual and/or a supplemental handout. Also cite the source(s) of the information found in the Chemical Properties & Safety table (part D). D. Chemical Properties & Safety: Make a table that lists the chemical properties of all reactants, reag.

1. (CHE 276) Organic Chemistry Laboratory Lab
References
Totah rev. 8/2011
5
The Laboratory Notebook
Your notebook will serve as a permanent record of your
experimental work. It will contain the
information you need to complete your work efficiently and
safely, and you will use the information
contained in your notebook to write laboratory reports
explaining your results. For these reasons, it is
important that your notebook be complete and accurate. As a
general rule, a good notebook is one from
which someone else can repeat your experimental work in the
same way that you have done it.
I. General Guidelines:
1. Your notebook must be bound, the pages numbered, and have
a carbon copy.
2. Write your name, the course name, and section # on the
cover or front page.

2. 3. Always use permanent ink, not pencil.
4. Write it down NOW. Your notebook is a log of what you do
as you do it.
5. Use complete sentences.
6. Write everything in your notebook. Weights, temperatures,
everything! When recording
experimental data, always include units.
7. Do not erase! If you make an error, draw a single line
through it, and continue. The original
statement should still be legible.
8. Never remove original pages from your notebook. You may
remove carbon copies.
9. Date every page as you use it.
10. Write legibly! If your notebook is illegible it will not be
graded.
II. The Notebook:
Each experiment recorded in your notebook should contain the
sections outlined below. A carbon
copy of your notebook pages will be collected at the end of each

3. laboratory period and will graded as
a part of your lab report. Late notebook pages will not be
accepted.
Sections A - E must be completed before you begin the
experiment. This is the prelab. Your TA will
verify that this section is complete. You will not be allowed to
proceed with the experiment if you
have not completed the prelab.
Section F, the Experimental, is recorded as you proceed each
day.
A. Title:
Give the experiment an accurate, descriptive title.
B. Purpose:
Discuss the general purpose of the experiment in two or three
sentences. If the experiment is a
synthesis (as opposed to a technique), write the chemical
equation, including reagents and
expected product(s). For multistep syntheses, write one equation
for each transformation, including
the preparation of reagents.
(CHE 276) Organic Chemistry Laboratory The Laboratory

4. Notebook
6
Totah rev. 8/2011
C. References:
Cite the reference upon which your experimental procedure is
based. In most cases this will be
your laboratory manual and/or a supplemental handout. Also
cite the source(s) of the information
found in the Chemical Properties & Safety table (part D).
D. Chemical Properties & Safety:
Make a table that lists the chemical properties of all reactants,
reagents, and solvents that you will
be using in the experiment as well as for the products you will
make. This table should include the
name of the compound, MW, density, mp, bp, etc. For each
compound, also list the toxicity (if
known), and any other important safety information (flammable,
corrosive, irritant, etc.). Some
useful references are provided at the end of this handout. A
sample table is shown below:
E. Research Plan:
This section will include specific instructions on how to
perform the lab. It must be complete
before you arrive. In combination with the Experimental
(Section F; completed during the
experiment), any reader should be able to repeat the experiment

5. as you did it based on what you
have written here. To prepare this section:
• Split the notebook page in half vertically (this has been done
for you in the notebook listed
for this course).
• Briefly outline the procedure you will follow on the left hand
side of the page. Leave the right
hand side blank. You will use it later to record procedural
modifications, data, and
observations when you actually perform the experiment (section
F).
• You do not need to use complete sentences when preparing
the research plan, but your
outline should provide enough detail that you can work directly
from your notebook, using
your lab manual only as a reference for clarification. Include
the amounts of reagents you
expect to use. As appropriate also record reagent purity and/or
concentration.
• Incorporate any changes that were made in the lab lecture.
• Use your own words. Do not copy directly from the text or
handout (this constitutes
plagiarism!).
• If there are multiple parts to an experiment, you must provide

6. an outline for each part.
• This is also the place to draw any specialized laboratory set-
ups that you will use.
F. Experimental:
This section of your notebook is written during the course of a
laboratory period, and should be
recorded on the right hand side of the pages that contain the
Research Plan (section E). An
example follows. This portion of the notebook is a record of
what you do as you do it. You do not
nead to rewrite the entire procedure, but you will need to note
any deviations from the Research
Plan. Record your data and observations completely and
accurately. The information included here
may help you understand later if your experiment was
successful, or what went wrong. This
section must be completed before you leave the lab for the day.
• Describe any changes to the procedure that you make during
the course of the experiment.
• Record the actual amount of reactants, reagents and solvents
that you use. Include units.

7. (CHE 276) Organic Chemistry Laboratory The Laboratory
Notebook
7
Totah rev. 8/2011
• Record your observations. Include any thoughts you have
about what may be going on. Note
any difficulties that you encounter.
• Make sure to record any melting points, boiling points,
weights, etc. before you leave the lab
whether you think you need them or not. Chances are that you
will. Drawings of TLC plates
should also be included here. Be sure your data is clearly
labelled such that someone else
would be able to figure out what it represents.
• Don’t forget to record the physical characteristics of any
compounds you isolate (e.g. solid,
liquid, shape of crystals, color, etc.). Has purification resulted
in any physical change?
• Other things you might wish to record: the formation and
identification of layers, the
evolution of heat or gas, the formation and characteristics of a
precipitate, reaction time,
unknown number if applicable, or your partners name (if any) -
for most experiments you
will work independantly.

8. • At the end of each day initial and date what you have written.
• Submit a carbon copy of your notebook pages to your TA
before you leave each day. These
pages will be graded as part of your laboratory report
(Appendix D). Late notebook
pages will not be accepted.
Below is an example of the research plan, with experimental
details, data, and observations filled in as
they would be during the laboratory period.
III. References:
The following references will be helpful as you complete your
prelab. You will find all of these
sources in the reference section (room 103) of the Science and
Technology Library or on the web.
Please familiarize yourself with them as you will use them
frequently throughout the semester.
General Chemical Properties & Safety:
1. Aldrich Catalog of Fine Chemicals. TP 202.A43
2. CRC Handbook of Chemistry and Physics QD 65.H231
3. The Merck Index RS 356.M524

9. 4. Dictionary of Organic Compounds QD 251.D5 1996
5. Lange's Handbook of Chemistry QD 65.L362
6. Hazardous Chemicals Desk Reference T55.3.H3 L49 2002
7. Sax's Dangerous Properties of Industrial Materials T55.3.H3
L494 2000
Resources on the Web:
1. SIRI MSDS Index * http://hazard.com/msds/index.php
2. Sigma-Aldrich Home Page http://www.sigmaaldrich.com
3. Reaxys www.reaxys.com (on campus only); cite primary
lit.
* The Materials Safety Data Sheet (MSDS) is the best source
for safety information. Many
chemical properties can also be found here.
(CHE 276) Organic Chemistry Laboratory The Laboratory
Notebook
8
Totah rev. 8/2011
IV. Sample Notebook Page
EXP NUMBER

10. EXPERIMENT/SUBJECT
DATE
9/15/10 37
NAME
Polly Ester
LOCKER/DESK NO COURSE & SECTION NO.
CHE 276, T 12:30pm (M004)
Synthesis of Isoborneol
Purpose: To synthesize isoborneol from camphor. To learn the
technique of gas
chromatography and use it to evaluate the ratio of reduction
products.
O
OH
H
H
OH
+
NaBH

11. 4
CH
3
OH
References: CHE 276 Organic Chemistry Lab Manual, 2007, pg
52.
SIRI MSDS Index http://hazard.com/msds/index.php
Properties & Safety:
compound MW
(g/mol)
mp
(°C)
bp
(°C)
density
(g/mL)
safety
camphor 152.24 179-180 --- --- harmful if swallowed
NaBH
4
37.8 --- --- --- severe irritant, may cause
burns, keep away frm water
methanol 32 --- 64 miscible toxic

12. ethyl ether 74 --- 35 0.71 flammable
isoborneol 154.25 212-214 --- --- flammable, irritant
Research Plan Experimental
1. Obtain about 0.1g of camphor
2. Combine with 0.5mL methanol in a
small test tube
3. Add 0.060g sodium borohydride in
portions
4. warm to reflux in a sand bath; heat
2 min
5. Analyze reaction mixture by TLC.
Develop plate in 25% ethyl acetate in
hexanes; vizualize with iodine.
camphor used: 0.106g (white solid)
used ethanol as solvent instead of
methanol
NaBH

13. 4
used: 0.059g 0.064g
some gas evolution observed (bubbles)
C = camphor
I = isoborneol
4cm 3.5cm
2.2cm
C I
CHEM 2423 Recrystallization of Benzoic Acid
Dr. Pahlavan
1
EXPERIMENT 4 - Purification - Recrystallization of Benzoic
acid
Purpose:
a) To purify samples of organic compounds that are solids at
room temperature
b) To dissociate the impure sample in the minimum amount of

14. an appropriate hot solvent
Equipment / Materials:
hot plate 125-mL Erlenmeyer flask ice
stirring rod spatula
Büchner funnel impure benzoic acid
weighing paper digital scales
rubber tubing (hose) benzoic acid
boiling stones (chips) filter paper
25 mL graguated cylinder 50 mL beaker Mel-temp
apparatus
Discussion:
The products of chemical reactions can be impure. Purification
of your products must be performed to remove
by-products and impurities. Liquids are customarily purified by
distillation, while solids are purified by
recrystallization (sometimes called simply "crystallization").
Recrystallization is a method of purifying a solid. There are
two types of impurities: those more soluble in a
given solvent than the main component and those less soluble.
(If there are any impurities that have the same
solubility as the main component, then a different solvent needs
to be chosen.)
When organic substances are synthesized in the laboratory or
isolated from plants, they will obviously contain
impurities. Several techniques for purifying these compounds
have been developed. The most basic of these
techniques for the purification of organic solids is
recrystallization, which relies on the different solubilities of
solutes in a solvent. Compounds, which are less soluble, will
crystallize first. The crystallization process itself
helps in the purification because as the crystals form, they

15. select the correct molecules, which fit into the crystal
lattice and ignore the wrong molecules. This is of course not a
perfect process, but it does increase the purity of
the final product.
The solubility of the compound in the solvent used for
recrystallization is important. In the ideal case, the
solvent would completely dissolve the compound to be purified
at high temperature, usually the boiling point of
the solvent, and the compound would be completely insoluble in
that solvent at room temperature or at zero oC.
In addition the impurity either would be completely insoluble in
the particular solvent at the high temperature,
or would be very soluble in the solvent at low temperature. In
the former case, the impurity could be filtered off
at high temperature, while in the latter case the impurity would
completely stay in solution upon cooling. In the
real world, this will never happen and recrystallization is a
technique that has to be practiced and perfected.
Regardless of crystallization method, the purity of the solid can
be verified by taking the melting point.
A good (suitable) recrystallization solvent will dissolve a large
amount of the impure compound at temperatures
near the boiling point of the solvent. Small amount of
compound being purified should remain in solution at low
temperatures, between approximately 25 and –5 oC. Low
solubility at low temperatures minimizes the amount
of purified compound that will lose during recrystallization.
CHEM 2423 Recrystallization of Benzoic Acid
Dr. Pahlavan
2

16. A suitable recrystallization solvent should also be partially
volatile in order to be easily removed from the
purified crystals. The solvent should not react with the
compound being purified and it should have the boiling
point below the melting point of the compound being purified
because solid melts before dissolves (oiling out).
In selecting a good recrystallization solvent one should also
consider flammability, toxicity, and expense.
In selecting a solvent consider that like likes like. Polar
compounds dissolve polar compounds and non-polar
compounds dissolve non-polar compounds. The most commonly
used recrystallization solvents are presented in
the following table.
solvent formula polarity boiling point (0C)
water H2O very polar 100
ethanol CH3CH2OH polar 78
methanol CH3OH polar 65
dichloromethane CH2Cl2 slightly polar 40
diethyl ether (CH3CH2)2O slightly polar 35
Organic compounds with one polar functional group and a low
number of carbon atoms such as methanol,
ethanol, and n-propanol are highly soluble (miscible) in water.
These alcohols form hydrogen bond with water
due to the polar –OH functional group. As the number of
carbons per polar functional group increase, solubility
decreases. The solubility of alcohols with four to five carbons is
given in the following table.
alcohol formula Solubility (g/100 ml H2O)

17. n-butanol CH3CH2CH2CH2OH 8
n-pentanol CH3CH2CH2CH2CH2OH 2
n-hexanol CH3CH2CH2CH2CH2CH2OH 0.5
n-pentanol CH3CH2CH2CH2CH2CH2CH2OH 0.1
Compounds with six or more carbons for each polar group will
not be very soluble in polar solvents but will be
soluble in non-polar solvents such as benzene and cyclohexane.
If a single solvent cannot be found that is suitable for
recrystallization, a solvent pair often used. The solvents
must be miscible in one another. Some commonly used solvent
pairs are water-ethanol, acetic acid – water,
ether-acetone. Typically, the compound being recrystallized
will be more soluble in one solvent than the other.
The compound is dissolved in a minimum amount of the hot
solvent in which it is more soluble.
The following formulas used in solubility problems.
% lost in cold solvent = (solubility in cold solvent/solubility in
hot solvent) x100
% recovery of solid = [g (solid ) – g (solid lost)] x 100 / g
(solid)

18. CHEM 2423 Recrystallization of Benzoic Acid
Dr. Pahlavan
3
Example (1)- The solubility of solid “X” in hot water (5.50
g/100 ml at 100 oC) is not very great, and its
solubility in cold water (0.53 g/100ml at 0 oC) is significant.
What would be the maximum theoretical percent
recovery from crystallization of 5.00 g of solid “X” from 100
ml water? Assuming the solution is chilled at 0
oC.
Percent solid lost in cold water = (solubility in cold water/
solubility in hot water) x100
= (0.53/5.50) x100 = 9.64%
grams solid lost in cold water = grams mass of original solid x
percent lost = 5.00 g x 9.64% = 0.482 g
g (solid recovered) = g (solid) – g (solid lost) = 5.00 – 0.482 =
4.52 g
% recovery = g (solid recovered) x100 / g (solid) = (4.52/5.00)
x100 = 90.4 %
Example (2) – The solubility of compound “X” in ethanol is
0.80 g per 100 ml at 0 oC and 5.00 g per 100 ml at
78oC. What is the minimum amount of ethanol needed to

19. recrystallize a 12.00 g sample of compound “X”?
How much would be lost in the recrystallization, that is, would
remain in the cold solvent?
amount of ethanol needed at 78 oC = (12.00 g)( 100 ml/5.00 g)
= 240 ml
amount of sample remaining in the cold solvent at 0 oC = (240
ml)(0.80 g/100 ml) = 1.9 g
or % lost = (0.80/5.00) x100 = 16 % 12.00 x 16% =
1.92 g
The actual laboratory we will do is the recrystallization of
benzoic acid from water using the temperature
gradient method. Benzoic acid is not very soluble in cold
water, but it is soluble in hot water. The purpose of
this experiment is to learn the technique of recrystallization by
purifying benzoic acid.

20. CHEM 2423 Recrystallization of Benzoic Acid
Dr. Pahlavan
4
Experimental Procedures
Using a weighing paper, weigh out about 1.00 g of “impure
Benzoic acid for recrystallization” and transfer it to
a 125-ml Erlenmeyer flask. Add about 20 ml distilled water,
using a graduated cylinder, to the flask and bring
the mixture to the boiling point by heating on a hot plate, while
stirring the mixture and boiling gently to
dissolve benzoic acid completely. (Fig 1)
benzoic acid
solution
Erlenmeyer
flask
hot plate
Fig 1- Dissolving benzoic acid

21. Remove the flask from the hot plate and examine the solution.
If there are particles of benzoic acid still
undissolved, then add an additional amount of hot or cold water
in small increments and resume heating the
solution. The objective is to dissolve the entire solid in only as
much as hot or near boiling solvent (water) as is
necessary. Do not add too much water or the solution will not
be saturated and the yield of purified benzoic
acid will be reduced. Keep adding water in small amounts
(several drops at a time from a Pasteur pipette) until
all of the benzoic acid is dissolved and the solution is boiling.
If the solution is completely clear (though not necessarily
colorless) and no solid benzoic acid is visible, then
add additional 10-15 ml water to the mixture and place the
Erlenmeyer flask on a countertop where it will not
be disturbed and cover with an upside-down small beaker (to
prevent dust contamination). Allowing the flask to
cool slowly will give the best-shaped crystals after about 5-10
minutes. If crystallization does not occur after 10
minutes, scrape the sides of the flask above the level of the
solution with the sharp end of a glass rod hard
enough to audibly scratch the interior surface of the flask. This
may dislodge some undetectable, small crystals
that will drop into the solution and "seed" the solution, helping
to induce crystallization. A seed crystal can
serve as a nucleation point for the crystallization process.
Cooling the solution in an ice bath may also help at
this point.

22. CHEM 2423 Recrystallization of Benzoic Acid
Dr. Pahlavan
5
When the crystals have formed completely (may required ice
bath), collect your solid chemical by setting up a
vacuum (suction) filtration on a properly fitted filter paper in a
clean Büchner funnel apparatus as described by
your instructor. (Fig 2)
vacuum(suction)
filtrate
benzoic acid
Buchner
funnel
Fig. 2 – Büchner funnel and suction flask
Pour the chilled mixture into the Buchner funnel. The water

23. should filter quickly - if not, check for vacuum
leaks. Get all the crystals out of the flask using a spatula or
stirring rod. Rinsing with 1 or 2 mLs of cold water
helps get the crystals out of the flask, and rinsing helps remove
impurities.
Let the aspirator run for a few minutes to start air-drying the
crystals. Then use a spatula to lift the filter paper
and crystals out of the Buchner funnel, then press them as dry
as possible on a large clean paper towel (hand
dry), allow them to dry completely, and transfer the dry sample
to a pre-weigh weighing paper. Determine the
weigh the DRY crystals of recovered benzoic acid.
Calculate the percent recovered using the following written
formula and determine the melting point of your
recrystallized benzoic acid.
Weight of benzoic acid obtained after
recrystallization
% Recovered =
x100
Weight of benzoic acid before
recrystallization
Note: Submit product to the instructor in a properly labeled
container.

24. CHEM 2423 Recrystallization of Benzoic Acid
Dr. Pahlavan
6
EXPERIMENT 4 – Recrystallization of Benzoic Acid
Data and Results (Recrystallization)
REPORT FORM Name _______________________________
Instructor ___________________________
Date ________________________________
1. Sample name ____________________________
2. Data on the impure Benzoic acid
a. Mass of the benzoic acid + weighing paper ________ g
b. Mass of weighing paper ________ g
c. Mass of impure benzoic acid ________ g
3. Data for recrystallized benzoic acid
a. Mass of recrystallized benzoic acid + weighing paper
________g
b. Mass of weighing paper ________ g
c. Mass of recrystallized benzoic acid ________g

25. d. Calculation of percentage recovery
(show calculation)
________%
d. Melting point of recrystallized benzoic acid
________ oC
e. Structural formula of the benzoic acid
CHEM 2423 Recrystallization of Benzoic Acid
Dr. Pahlavan
7
Pre-Laboratory Questions–EXP 4 Name:
Due before lab begins. Answer in space provided.
1. What is the ideal solvent for crystallization of a particular
compound? What is the primary consideration in
choosing a solvent for crystallizing a compound?

26. 2. Impure benzoic acid was dissolved in hot water. The
container of solution was placed in an ice-water bath
instead of being allowed cooling slowly. What will be the
result of cooling the solution in this manner?
3. Outline the successive steps in the crystallization of an
organic solid from a solvent and state the purpose of
each operation.
4. Compound X is quite soluble in toluene, but only slightly
soluble in petroleum ether. How could these
solvents be used in combination in order to recrystallize X?
5. 0.12 g of compound “Y” dissolves in 10 ml of acetone at 25

27. oC and 0.85 g of the same compound dissolves
in 10 ml of boiling acetone. What volume of acetone would
be required to purify a 5.0 g sample of
compound?
CHEM 2423 Recrystallization of Benzoic Acid
Dr. Pahlavan
8
Post-Laboratory Questions–EXP 4 Name:
Due after completing the lab.
1. Give some reasons why Suction filtration (vacuum) is to be
preferred to gravity filtration.
2. A student recrystallized some impure benzoic acid and
isolated it by filtration. He scraped the purified
benzoic acid off the filter paper after it had dried and took
the melting point as a test for purity. He was
surprised that most of the white solid melted sharply
between 121 and 122oC but that a small amount

28. remained unmelted even at temperatures above 200oC.
Explain this behavior.
3. What does the term “oiling out” mean? How can one
prevent oiling out?
3. What are the purposes of the following in recrystallization of
solids?
I) boiling stones –
II) activated carbon -
III) seed crystals –
4. Give one reason why we cannot reuse boiling chips?
5. 0.12 g of compound “Y” dissolves in 10 ml of acetone at

29. 25 oC and 0.85 g of the same compound
dissolves in 10 ml of boiling acetone. If 5.0 g of
compound “Y” were to be recrystallized from 75 ml
acetone, what will be the next maximum amount of “Y”
that will be recrystallized?
EXPERIMENT 4 - Purification - Recrystallization of Benzoic
acid Discussion:EXPERIMENT 4 – Recrystallization of
Benzoic AcidPre-Laboratory Questions–EXP 4 Name:Post-
Laboratory Questions–EXP 4 Name:
Esterification reaction: the synthesis and purification of 2-
Acetoxybenzoic acid and subsequent analysis of the pure
product (acetylsalicylic acid ) via Thin-Layer Chromatography.
Andra C. Postu
Department of Chemistry, American University, Washington,
D.C. 20016
Date of Publication: February 25, 2014
ABSTRACT: An esterification reaction was performed in order
to convert salicylic acid to acetylsalicylic
acid, the prodrug and active ingredient in Aspirin. Salicylic acid
is made less acidic by converting its
alcohol functional group into an ester so that it is less damaging
to the digestive system in the human
body. The purpose of the experiment is to synthesize, isolate,
and purify 2-acetoxybenzoic acid and
analyze salicylic acid, crude product, and acetylsalicylic acid
via Thin-Layer Chromatography to
determine if pure aspirin was synthesized. The amount of crude
aspirin synthesized was 3.029 grams
and the amount of pure aspirin synthesized was 2.169. The
theoretical yield was 2.520 grams. Thus,
there was a percent error of 13.93 % and percent yield of

30. 86.07%. TLC analysis showed that
acetylsalicylic had a higher Rf value than salicylic acid (.800
vs. .315 Rf value, respectively). The salicylic
acid was more polar because of its extra polar functional group
and did not travel as far. Thus, pure
aspirin was synthesized.
INTRODUCTION
2-Acetoxybenzoic acid, more commonly known as Aspirin, is a
white, crystalline
substance most commonly known for its pain-relieving
qualities1,2. Acetylsalicylic acid (active
ingredient of Aspirin) is an acetyl derivative of salicylic acid
and the prodrug of the active
metabolite, salicylic acid.2 Aspirin is a salicylate drug because
it is an ester of salicylic acid. It is
commonly known for its pain relieving properties. However, it
does not only serve as an
analgesic but also as an antipyretic, anti-inflammatory, and
antiplatelet medication2. The main
metabolite of acetylsalicylic acid, salicylic acid, is an essential
part of the human metabolism3.
Salicylic acid is an integral part of pain management and was
often used by ancient cultures,
such as the Native Americans, who extracted the chemical from
willow tree bark3. This

31. fundamental compound can cause stomach irritation and is bitter
tasting, so a milder prodrug
called acetylsalicylic acid was synthesized in 1893 by the
German chemist Felix Hoffmann who
worked for Bayer2,3,4. Acetylsalicylic acid is a type of drug
that is formulated deliberately so that
it will deteriorate in the body into the active drug5. This
prodrug was developed because it is
much less abrasive when delivered to the body and is much
more easily absorbed6. The active
drug, salicylic acid, is the active metabolite because it is the
form of the drug after the body has
processed it. Edward Stone of Oxford University discovered
salicylic acid in 1763 from the bark
of willow tree4,5,6.
Aspirin works by suppressing the synthesis of prostaglandins
and thromboxanes in the
human body3,4,5. Prostaglandins function as local hormones
produced in the body that aid in the
transmission of pain signals, regulate the hypothalamic
thermostat, and inflammation2.
Thromboxanes are involved in the aggregation of platelets that
form blood clots. It does this by

32. the irreversible inactivation of prostaglandin-endoperoxide
synthase (PTGS), also known as
cyclooxygenase 2, an enzyme that is needed in the synthesis of
prostaglandin and thromboxane.5
Aspirin serves as the acetylating agent where an acetyl group is
covalently attached to a serine
residue in the active site of the prostaglandin-endoperoxide
synthase enzyme. The ability of
aspirin to diminish inflammation is due to its inhibition of the
synthesis of prostaglandins.
Aspirin alters the oxygenase activity of prostaglandin
synthetase by moving the acetyl group to a
terminal amine group4.
Though aspirin has numerous benefits, there are several adverse
affects as well. It is
particularly damaging to the stomach lining and there is an
increased risk of gastrointestinal
bleeding3,5. The risk of stomach bleeding increases with use of
drugs such as warfarin and
alcohol6. Large doses can cause a ringing in the ears, or
tinnitus. Some people may have allergy-
like symptoms including hives and swelling because of a
possible salicylate intolerance1. Aspirin

33. can cause swelling of skin tissues (angioedema), increase risk
of Reye’s syndrome and can cause
hyperkalemia1,2,3. Although most commonly known for its
anti-inflammatory properties and
pain-reducing qualities, acetylsalicylic acid is also an effective
fever-reducer and has been to
shown to prevent the progression of existing cardiovascular
issues such as heart attacks or
strokes in low does on a long term basis. Aspirin’s antiplatelet
effects come from its ability to
inhibit the synthesis of thromboxane, which otherwise bind
platelets together in areas where
vessel damage has occurred 4 . These platelets can clot together
and become harmful otherwise. It
also controls fevers through a similar mechanism (prostaglandin
system) and the inhibition of
PTGS that is not reversible5.
Thin Layer Chromatography (TLC) is a chromatography
technique that is used to
separate mixtures that are non-volatile such as salicylic acid,
acetylsalicylic acid, and the crude
acetylsalicylic acid product3,4. A sheet is coated with an
absorbent material such as silica gel and

34. serves as the stationary phase. The samples are placed on the
sheet and a solvent (mobile phase)
moves up the stationary phase via capillary action. Various
substances move up the stationary
phase at different rates depending on their polarity and
attraction to the stationary phase itself3.
Like substances dissolve like substances. Because silica gel is
very polar, the affinity of polar
substances to the silica gel will prevent them from moving very
far up the TLC plate. Non-polar
substances will move further up the TLC plate and be close to
the solvent front. The hydroxyl
groups present on the surface of silica gel can be modified so
that they separate things in varying
parameters depending on need. TLC is used to confirm the
purity of acetyl salicylic acid and
compare the polarity of other components of the reaction
(salicylic acid and crude product)3. The
solvent was a nonpolar 9:1 mixture of ethyl acetate and
methylene chloride respectively3.
The active ingredient of the drug Aspirin, acetylsalicylic acid
can be synthesized through
an esterification reaction between salicylic acid and acetic
anhydride. This type of interaction

35. involves a reaction of a carboxylic acid with an alcohol in order
to form a carboxylate ester2,3.
Salicylic is a weak acid with an alcohol functional group
attached to it. The products of the
reaction between salicylic acid and acetic anhydride are
acetylsalicylic acid and acetic acid3.
MATERIALS AND METHODS
Synthesis
2.0 grams of salicylic acid, 5.0 mL of acetic anhydride and 5
drops of 85% phosphoric
acid solution were placed into a 50 mL Erlenmeyer flask. A 70-
80 °C hot water bath was
prepared by placing a 250 mL beaker on a hot plate with a
thermometer to monitor temperature.
The 50 mL Erlenmeyer flask with the mixture of salicylic acid,
acetic anhydride, and phosphoric
acid was partially submerged in the water bath and heated for
15 minutes until vapors ceased to
be released. After 10 minutes of heating the submerged flask
passed, 2 mL of distilled water was
added to the flask. Then, once the reaction reached completion
the flask was removed and 20 mL
of distilled water was added. The flask was left to cool to room
temperature before being placed

36. in an ice bath for 5 minutes to allow crystallization to occur. A
vacuum filtration was set up and
the mixture was filtered via vacuum filtration. Once the liquid
had been drawn out of the
mixture, the crystals were washed with 5 mL of cold, distilled
water. This was repeated once
more. The vacuum filtration apparatus was left on for several
minutes to aid in the drying of the
solid product before it was weighed and recorded3.
Purification
About 5 mg of crude acetylsalicylic acid were set aside for
TLC analysis. The remaining
crude aspirin was added to a 125 mL Erlenmeyer flask. About
60 mL of hot ethanol/water
solvent was added slowly to the crude aspirin in a warm water
bath. Once the crystals dissolved,
the flask was covered and left to cool to room temperature
before it was placed in an ice bath for
10 minutes to fully crystallize. Then, the crystals were placed
into a vacuum filter where they
were subsequently rinsed with two 3 mL portions of cold
deionized water and one 2 mL portion

37. of cold ethanol3.
TLC Analysis
A developing chamber was made by using a 400 mL beaker and
watch glass. 10 mL of
9:1 mixture of ethyl acetate and methylene chloride respectively
was placed inside the beaker
with a 110 mm filter paper in order to saturate the chamber with
solvent vapors. The solvent was
left to travel to the top of the filter paper before the silica gel
coated TLC plate was placed inside
of the beaker. 3 mg of each salicylic acid, crude product, and
recrystallized product was place
inside three separate small beakers and dissolved with 6 drops
of TLC solvent. A different pipette
was then used for each of the three samples to lightly spot the
TLC plate at the light pencil hash
mark about ½ inch from the bottom of the plate. The plate was
left to develop until the solvent
front was about ½ inch away from the top of the TLC plate. The
plate was then removed from
the developing chamber and the solvent front was promptly
marked. The plate was left to dry
before it was examined under UV light3.

38. RESULTS
Figure 1: Structure of Salicylic Acid, Acetic anhydride, and
Acetyl salicylic acid
The structures of salicylic acid, acetic anhydride, and
acetylsalicylic acid are pictured above with
their functional groups clearly visible in red.
Mass= Density x Volume (Eq.1)
Mass (g) acetic anhydride used= (1.08 g/mL) x (5.00 mL)
Mass (g) acetic anhydride= 5.40 g
Mass of aspirin synthesized (g)= (Mass of aspirin and filter
paper) – (Mass of filter paper) (Eq.2)
Mass of aspirin synthesized (g)= (3.159 g)-(.1300 g)
Mass of aspirin synthesized (g)= 3.029
Mass of purified aspirin product (g)= (Mass of purified aspirin
and filter paper)- (mass of filter paper) (Eq.3)
Mass of purified aspirin product (g)= (2.299 g)- (.1300 g)
Mass of purified aspirin product (g)=2.169
Table 1: Synthesis of Aspirin Data
Salicylic Acid
Acetic anhydride
Acetylsalicylic acid
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http://www.chemspider.com/Chemical-Structure.
2157.html

39. "
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331.html
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http://www.chemspider.com/Chemical-Structure.
7630.html
Mass of salicylic acid used (g) 2.009
Volume of acetic anhydride used (mL) 5.000
Mass of acetic anhydride used (1.08 g/mL) used (g) 5.400
Mass of aspirin and filter paper (g) 3.159
The table above depicts the various masses and volumes of
calculated and raw data in the
synthesis of aspirin. 2.009 grams of salicylic acid was used with
5.000 mL of acetic anhydride.
The calculated mass of acetic anhydride was calculated using
it’s known density for a mass of
5.400 grams. The mass of aspirin and filter paper was 3.159
grams. The mass of the filter paper
was .1300 grams. Thus, the calculated value of crude
synthesized aspirin was 3.029 grams.
Following purification, the calculated mass of the final aspirin
product was 2.169 grams.
Theoretical Yield (Eq.4)
2.0 g salicylic acid (1 mole/138.0 g) = 0.014 moles
5 mL acetic anhydride (1.08 g/mL) = 5.4 g
5.4 g (1 mole/102 g) = 0.05 moles
There is a smaller molar amount of salicylic acid so it is the

40. limiting reagent.
Therefore, the theoretical yield of acetylsalicylic acid is 0.014
moles.
0.014 moles acetylsalicylic acid (180 g/mole) = 2.52 g
Percent Error =(experimental mass - theoretical mass) /
theoretical value x 100% (Eq.5)
Percent Error=(2.169-2.520)/2.520 x 100
Percent Error=13.92 %
Percent Yield = (experimental mass/theoretical mass) x 100%
(Eq. 6)
Percent Yield=(2.169/2.520) x 100
Percent Yield= 86.07 %
Table 2: Theoretical Yield, Percent Error, and Percent Yield
The calculated theoretical yield was 2.520 grams. Thus, the
percent error was 13.93 % and the
percent yield was 86.07%.
Figure 2: TLC Plate with Salicylic Acid, Crude Product, and
Final Product under UV Light
Mass of filter paper (g) .1300
Mass of crude aspirin synthesized (g) 3.029
Mass of purified aspirin product (g) 2.169
Theoretical Yield (g) 2.520
Percent Error 13.93 %
Percent Yield 86.07%

41. "
Pictured above is the TLC plate with salicylic acid, crude
product, and final purified produce
under UV light, respectively. The final product (acetylsalicylic
acid) traveled the furthest up the
TLC plate. The salicylic acid travelled the smallest distance.
Rf Value= (distance from start to center of substance/distance
from start to solvent front) (Eq. 7)
Rf Value= (2.0 cm/6.35 cm)
Rf Value=.315
Table 3: Rf Values of Salicylic Acid, Crude Product, and Final
Product from TLC Analysis
The salicylic acid travelled the smallest distance with and Rf
value of .315. Crude acetylsalicylic
acid had an Rf value of .480. The purified acetylsalicylic acid
product traveled the furthest up the
TLC plate with an Rf value of .800.
DISCUSSION
The esterification reaction is a term for a general reaction in
which two reactants, an
alcohol and an acid, form an ester in the final product2. This
reaction can be used to synthesize
aspirin from salicylic acid. These types of reactions are
typically reversible, so most
esterification reactions are equilibrium reactions. Le Chatelier’s
principle is a pillar of modern
chemistry that states that any change imposed on a system that

42. is in equilibrium will cause the
system to adjust to a new equilibrium in order to counteract the
change2. The reaction is slow in
pure acetic anhydride, therefore phosphoric acid was used as a
catalyst for the reaction because it
is a strong acid2. According to Le Chatelier’s principle, an
excess amount of acetic anhydride
Salicylic Acid Rf value .315
Crude Acetylsalicylic Acid Rf value .480
Pure Acetylsalicylic Acid Rf value .800
would force the equilibrium towards the desired product,
acetylsalicylic acid. This mechanism
would cause the reaction to favor the product side (aspirin and
acetic acid).The solution was also
heated in order to accelerate the approach to equilibrium2,3.
Salicylic acid contains two acidic functional groups, a
carboxylic acid and an a phenol
group2. The alcohol group (more specifically, the phenol group)
in the salicylic acid participates
in the reaction because it undergoes esterification and forms an
acetylated ester. The human acid
is acidic, but the acidity of salicylic acid is great and can thus
be very damaging to the digestive
system. It can cause gastric and intestinal bleeding as well as
stomach ulcers to form. The acidy
is to harsh on the lining of the stomach, so “covering up” or
removing one of the acidic portions
of salicylic acid and leaving the carboxylic acid part with an
acetyl group makes it much less
damaging to the body and makes absorption much easier2. It is

43. for this reason that acetylsalicylic
acid is the active ingredient in Aspirin and serves as the
prodrug. Aspirin works by irreversibly
inhibiting cyclooxygenase 2 (COX-2) also known as PTGS and
prevents the synthesis
prostaglandins and thromboxane, which are involved in damage
repair in tissues via
inflammation, clotting, pain signaling, and temperature
regulation5,6.
The overall mechanism of reaction that is taking place in the
synthesis of aspirin is much
more complex than one would guess. Basically, an esterification
reaction such as the synthesis of
aspirin occurs when a carboxylic acid and an alcohol combine in
a reaction to produce an ester. A
molecule of water splits off and the remaining carboxylic acid
and alcohol form the ester in its
place. In the reaction, the phenoxide ion (OH on the ring) is
stabilized by the electron
withdrawing carbonyl group on the salicylic acid, making it a
very stable nucleophile. The
carbonyl carbon of the acetic anhydride is makes it an excellent
electrophile because the leaving
group or acetate ion is stabilized by the acidic conditions
provided by the phosphoric acid
catalyst. Firstly, protonation of acetic anhydride make it an
even better electrophile. It takes a
proton from phosphoric acid, leaving it with a negative charge.
The nucleophile, salicylic acid
attacks the carbonyl carbon on acetic anhydride and bonds. A
bond forms between the carbonyl
carbon of acetic anhydride and the oxygen (partial positive
charge) from the –OH group of
salicylic acid form a bond. Phosphoric acid deprotonates the
intermediate and removes the
hydrogen atoms that is bonded to the oxygen with the partial

44. positive charge. This forms a
tetrahedral intermediate and phosphoric acid is thus
regenerated. An acetate anion is present and
removes the hydrogen attached to oxygen on the intermediate.
The removal of this hydrogen
gives rise to an ester, and thus the product acetylsalicylic acid.
Acetic acid is also formed.
Phosphoric acid is essential in this reaction because it acts as a
catalyst that (combined with heat)
helps the reaction occur in a decent amount of time. It is a
liquid acid and thus does not contain a
large amount of water that would otherwise affect the yield of
the reaction. It also has a strong
conjugate base, which is important because this is a reversible
reaction. The reaction was placed
in a hot water bath and heated to 70-80 °C to help the reaction
occur at a faster rate because
adding heat to a system increases the energy present and
particles move and collide at a faster
rate. Otherwise, the reaction would take too far to long to react
and the equilibrium would not
favor the product side (aspirin and acetic acid). After heating
the reaction, distilled water was
added to help with recrystallization and to decompose any
remaining acetic anhydride because it
strongly reacts with water. There is remaining acetic anhydride
because salicylic acid is the
limiting reagent and acetic anhydride is present in excess. It is
important to consider that
acetylsalicylic acid is not the only product that forms, acetic
acid is another byproduct of the
reaction. The objective is to isolate pure acetylsalicylic acid. A
hot water/ ethanol mixture (about

45. 20 mL hot solvent of water/ethanol per gram crude aspirin) is
used to further purify aspirin by
removing acetic acid3. The acetic acid is very soluble in water
and can be removed from aspirin,
which is less polar and interacts with the ethanol portion of the
mixture. A purified product is
obtained after recrystallization of crude aspirin in the hot
ethanol.
After Thin Layer Chromatography was performed, the
determined Rf values were .315, .
480, and .800 for salicylic acid, crude aspirin, and purified
aspirin respectively. An 86.07 % yield
of purified acetylsalicylic acid was obtained. TLC analysis
demonstrates that pure aspirin was
synthesized. This is noted because of the high Rf value of the
pure aspirin. The solvent mixture
allowed for the greatest separation between samples. Aspirin
traveled very far up the solvent
front because it is much less polar that salicylic acid because
one of its acidic, or polar functional
groups (-OH) was converted to an ester. Salicylic acid is much
more polar because of its
carboxylic acid group and the alcohol it contains. Therefore,
salicylic acid was more attracted to
the polar stationary phase (silica gel) and did not move as far up
the TLC plate as acetylsalicylic
acid. Aspirin was more attracted to the mobile phase (solvent
that was relatively nonpolar) that
the stationary phase. The crude product has a Rf value that is
between the salicylic acid and
aspirin because of the presence of acetic acid that interacts with
polar stationary phase.
There are many potential sources of error, including the
constant threat of left over
product on glassware. A large source of error could have been
omitting to wash the newly

46. synthesize crude aspirin crystals with cold distilled water three
times. The crystals were only
rinsed once with room temperature distilled water. This would
could have added to the 13.93%
error because a large amount of acetic anhydride may have not
been removed, thus
contaminating the product. Another source of error could have
been that the entirety of the crude
product (about 3 grams) was dissolved in the hot water/ethanol
solvent and crystallized rather
than one gram. Dealing with more crystals can maximize loss of
product because you are dealing
with a greater number of substance. A great deal of product
could have been lost during vacuum
filtration.
CONCLUSION
A total of 2.169 grams of pure aspirin was synthesize out of a
possible yield of 2.52
grams. Thus, there was a 13.93 % error and 86.07% product
yield. TLC analysis further
confirmed these results due to the observation that aspirin had a
higher Rf value that salicylic
acid (.800 vs. .315, respectively), thus demonstrating that the
one of polar functional groups had
been converted to an ester. This makes aspirin less acidic and
therefore less damaging to the
digestive system of the human body. In the future, special care
should be given to the washing of
the crystals with cold distilled water to maximize yield. Also, a
stronger acid catalyst such
sulfuric acid could be used to further increase the rate of
reaction.

47. Mechanism 1: Reaction between salicylic acid,
phosphoric acid, and acetic anhydride
Mechanism 2: Reaction of Water and byproducts
REFERENCES
(1) Pehlic, E.; Nuhanovic, M.; Sapcanin, A.; Banjanin…, B.
Characterization of acetylsalicylic
acid with thin-layer chromatography and hot--stage microscopy
depending to solvent system.
2012.
(2) Klein, D. Organic Chemistry: 2nd ed.;Wiley:Hoboken, 2013.
(3) Williamson, K and Katherine Masters. Macroscale and
Microscale Organic Experiments, 6th
ed.; Brooks/Cole, 2011.
(4)Rainsford, K. History and development of the salicylates.
Aspirin and Related Drugs 2004, 1–
23.
(5)Olmsted, J. A. Synthesis of Aspirin: A General Chemistry
Experiment. Journal of Chemical
Education 1998, 75.
(6)Truelove, J.; Hussain, A.; Kostenbauder, H. Synthesis of 1-
O-(2’-acetoxy)benzoyl-alpha-D-2-
deoxyglucopyranose, a novel aspirin prodrug.Journal of
pharmaceutical sciences 1980, 69, 231–
2.
Andra Postu

48. Organic Chemistry Lab II
Lab Partner: Michael Bible
February 19, 2014