Organic Chem Lab Reports (Purification – Recrystallization of Benzoic acid)

Attached here is a lab report I need done by tomorrow night 19:00 EST. This report must be at least 6 pages long (that’s excluding title page and references). I need you to insert compounds, diagrams etc. attached is a sample of an old lab report you can use for guidance. DO NOT PLAGIARIZE. You can get pictures online but your sources must be cited at the reference page.

CHEM 2423 Recrystallization of Benzoic Acid Dr. Pahlavan

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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 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 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

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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) 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)

CHEM 2423 Recrystallization of Benzoic Acid Dr. Pahlavan

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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 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.

CHEM 2423 Recrystallization of Benzoic Acid Dr. Pahlavan

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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

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.

CHEM 2423 Recrystallization of Benzoic Acid Dr. Pahlavan

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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 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.

CHEM 2423 Recrystallization of Benzoic Acid Dr. Pahlavan

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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

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

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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?

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 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

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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
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 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 Acid
Pre-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 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

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

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

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

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

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

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

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.

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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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 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%

”

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 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 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 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
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
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.

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
Organic Chemistry Lab II

Lab Partner: Michael Bible
February 19, 2014

__________________________________________________________________________________________________________________
1

 

Topic
 4:
 Writing
 an
 Organic
 Chemistry
 Lab
 Report
 

Written
 by
 
Danielle
 M.
 Solano
 

Department
 of
 Chemistry
 &
 Biochemistry
 
California
 State
 University,
 Bakersfield
 

General
 Information
 
Unless
 otherwise
 indicated,
 always
 write
 your
 report
 as
 if
 you
 are
 submitting
 a
 paper
 to
 the
 Journal
 
of
 Organic
 Chemistry
 (view
  J.
 Org.
 Chem.
 2012,
 77,
 11296-­‐11301
 or
 any
 other
 recent
  Journal
 of
 
Organic
 Chemistry
 article
 for
 a
 good
 example).
 This
 means
 that
 you
 must
 adhere
 to
 the
 American
 
Chemical
 Society
 (ACS)
 standards
 for
 formatting,
 including
 citations
 and
 references.
 
 

General
 Lab
 Report
 Guidelines
 
1. Title
 all
 sections
 of
 your
 lab
 report.
 There
 should
 be
 no
 question
 as
 to
 which
 section
 is
 which.
 

Your
 lab
 report
 should
 include
 all
 of
 the
 following
 sections:
 Abstract,
 Introduction,
 Results
 and
 
Discussion,
 Conclusions,
 Experimental
 Section,
 and
 References.
 

2. Use
 formal,
 professional
 prose.
 Do
 not
 use
 contractions
 or
 colloquialisms.
 
 

3. Never
  use
  “I”
  or
  “my”.
  While
  the
  occasional
  “we”
  is
  acceptable,
  you
  should
  never
  refer
  to
 
yourself
 or
 other
 individuals.
 Also
 avoid
 “the
 student”,
 “the
 experimenter”,
 or
 “one”.
 

4. Be
 clear
 and
 concise.
 Try
 to
 state
 what
 you
 need
 to
 as
 understandable
 as
 possible
 and
 in
 as
 few
 
words
 as
 possible.
 

5. Do
 not
 use
 quotes.
 If
 you
 are
 explaining
 information
 from
 a
 reference,
 restate
 it
 in
 your
 own
 
words,
 and
 then
 use
 an
 in-­‐text
 citation
 in
 the
 style
 of
 the
 American
 Chemical
 Society.
 

6. Proofread
 your
 work.
 Spelling
 and
 grammar
 errors
 are
 unacceptable.
 It
 is
 recommended
 that
 
you
  add
  chemistry
  words
  to
  your
  word
  processor’s
  dictionary
  so
  that
  they
  can
  easily
  be
 
detected.
 

7. Assume
 the
 reader
 is
 an
 organic
 chemist,
 but
 knows
 nothing
 about
 your
 experiment.
 For
 
example,
 write
 your
 report
 as
 if
 you
 are
 explaining
 your
 results
 to
 an
 organic
 chemistry
 student
 
at
 a
 different
 university.
 Do
 not
 make
 assumptions
 that
 they
 know
 what
 the
 melting
 point
 is
 
supposed
 to
 be,
 or
 why
 you
 used
 the
 techniques
 you
 did.
 Explain
 everything.
 

Every
 Lab
 Report
 Must
 Include…
 
1. Title.
 Your
 title
 should
 be
 clear
 and
 accurate.
 It
 does
 not
 have
 to
 be
 the
 title
 of
 the
 experiment
 

as
 listed
 in
 your
 lab
 manual.
 Feel
 free
 to
 get
 creative.
 
 

2. Authors.
 If
 you
 are
 writing
 the
 report
 with
 a
 partner
 or
 a
 team,
 be
 sure
 to
 include
 everyone’s
 
name.
 

3. Abstract
 (1
 paragraph):
 Your
 abstract
 should
 summarize
 the
 purpose
 of
 your
 study,
 the
 main
 
results,
 and
 your
 major
 conclusions.
 Abstracts
 are
 typically
 2-­‐5
 sentences
 in
 length
 (200
 word
 

__________________________________________________________________________________________________________________
2
 

maximum)
 and
 are
 usually
 published
 separately
 from
 the
 article
 in
 order
 to
 attract
 readers.
 As
 
such,
 they
 should
 not
 contain
 any
 references
 or
 
 abbreviations.
 

4. Introduction
  (1-­‐3
  paragraphs):
  Here
  is
  where
  you
  explain
  why
  you
  are
  conducting
  the
 
experiment.
  Technically,
  this
  section
  can
  be
  written
  BEFORE
  you
  actually
  conduct
  the
 
experiment
  and
  thus
  your
  approach
  should
  reflect
  that.
  Include
  applicable
  background
 
information,
 and
 clearly
 state
 the
 purpose
 and
 objectives
 of
 the
 study
 (what
  is
 the
 scientific
 
problem
 that
 you
 are
 addressing?).
 If
 applicable,
 state
 your
 initial
 hypothesis.
 Also
 outline
 your
 
experimental
  strategy
  (don’t
  include
  experimental
  details;
  just
  explain
  your
  general
  plan
  of
 
attack
 in
 a
 sentence
 or
 two).
 Use
 present
 tense,
 and
 lots
 of
 in-­‐text
 citations.
 Do
 not
 include
 any
 
experimental
 results
 or
 conclusions.
 

5. Results
  and
  Discussion
  (2
  or
  more
  paragraphs):
  Note
  that
  organic
  chemistry
  journals
 
typically
 combine
 the
 results
 and
 discussion
 in
 the
 same
 section
 (many
 other
 journals
 separate
 
these
 sections).
 This
 is
 where
 you
 explain
 your
 experiment,
 how
 it
 worked,
 the
 results
 you
 got,
 
and
 what
 those
 results
 mean.
 While
 you
 should
 talk
 about
 (and
 explain)
 your
 experiment
 here,
 
remember
 to
 save
 the
 details
 (like
 amounts
 of
 reagents
 used,
 etc.)
 for
 the
 experimental
 section.
 
Explain
 how
 your
 experiment
 worked,
 and
 the
 purpose
 of
 each
 step
 and/or
 component.
 Then
 
describe
 each
 result
 and
 what
 information
 it
 gave
 you
 (i.e.,
 discuss
 your
 hypothesis,
 then
 how
 
and
 why
 your
 results
 support
 or
 contradict
 your
 hypothesis).
 When
 discussing
 a
 product,
 be
 
sure
 to
 address
 issues
 such
 as
 product
 identification,
 purity,
 and
 percent
 yield.
 Compare
 your
 
results
  to
  those
  in
  the
  literature
  (and
  be
  sure
  to
  include
  in-­‐text
  citations
  when
  citing
 
information
 from
 the
 literature).
 If
 your
 results
 are
 inconclusive
 or
 inconsistent,
 mention
 that
 
here
 and
 suggest
 possible
 sources
 of
 error.
 

Don’t
 forget
 to
 include
 any
 applicable
 figures,
 schemes,
 and/or
 tables.
 All
 schemes
 must
 contain
 
skeletal
 structures
 and
 be
 drawn
 in
 ChemDraw
 or
 a
 similar
 chemistry
 drawing
 program
 (photos,
 
hand
 drawn
 schemes,
 and
 materials
 that
 are
 not
 your
 own
 is
 unacceptable).
 Be
 sure
 to
 include
 
all
 reagents
 in
 your
 scheme
 and
 a
 percent
 yield.
 Additionally,
 every
 figure,
 scheme,
 and
 table
 
must
 contain
 a
 title
 and
 a
 number.
 (You
 may
 also
 opt
 to
 number
 the
 structures
 in
 your
 scheme,
 
which
 makes
 referring
 to
 the
 structures
 in
 the
 text
 of
 your
 report
 much
 easier.)
 

6. Conclusions
  (1
  paragraph):
  Summarize
  your
  main
  findings
  and
  explain
  why
  they
  are
 
significant.
 Suggest
 studies
 you
 might
 conduct
 to
 confirm
 your
 results
 or
 build
 on
 your
 results
 if
 
you
 had
 more
 time
 and/or
 resources.
 

7. Experimental
 Section
 (1
 or
 more
 paragraphs):
 Yes,
 this
 section
 comes
 after
 the
 conclusions.
 
Include
  enough
  detail
  so
  that
  a
  peer
  could
  reproduce
  your
  results
  (if
  you
  keep
  a
  good
  lab
 
notebook,
  you
  will
  just
  have
  to
  type
  up
  what
  you
  wrote
  in
  it).
  Don’t
  forget
  to
  include
  any
 
important
 observations
 such
 as
 colors
 of
 solution,
 appearance
 of
 crystals,
 yields
 (grams
 and
 
percent
 yield),
 melting
 points
 (for
 melting
 points,
 report
 uncorrected
 mp,
 apparatus
 number,
 
calibration
 curve,
 and
 corrected
 mp),
 Rf
 values,
 and/or
 spectroscopic
 data
 (any
 IR
 and
 1H
 NMR
 
values
 must
 be
 reported
 in
 ACS
 format).
 Be
 sure
 to
 use
 past
 tense
 to
 describe
 what
 you
 did,
 and
 
use
 passive
 voice
 (e.g.,
 instead
 of
 saying
 “I
 put
 HCl
 in
 the
 flask”
 or
 “Add
 HCl
 to
 the
 flask”,
 say
 
“HCl
 was
 added
 to
 the
 flask”).
 

8. References:
  Helpful
  in
  case
  someone
  wants
  to
  reproduce
  your
  study
  and/or
  confirm
  your
 
findings.
 You
 should
 be
 sure
 to
 cite
 your
 references
  in
 text
 and
  list
  them
 in
 the
 style
 of
  the
 
American
 Chemical
 Society
 (ACS).
 Don’t
 forget
 to
 include
 obvious
 references
 like
 the
 lab
 manual
 
and/or
 textbook.
 

__________________________________________________________________________________________________________________
3
 

The
 ACS
 Format
 for
 Citing
 and
 Listing
 References
 
For
 formal
 lab
 reports,
 you
 must
 use
 the
 American
 Chemical
 Society
 (ACS)
 style
 for
 citation
 and
 
referencing.
 You
 must
 use
 superscript
 numbers
 in
 the
 text
 when
 you
 refer
 to
 information
 from
 a
 
reference.
 The
 numbers
 should
 be
 listed
 in
 order
 as
 they
 appear
 in
 your
 paper,
 and
 the
 list
 should
 
be
 included
 at
 the
 end
 of
 your
 report.
 If
 you
 refer
 to
 a
 reference
 twice,
 you
 can
 just
 use
 the
 same
 
number
  both
  times.
  View
  J.
 Org.
 Chem.
  2012,
  77,
  11296-­‐11301
  or
  any
  other
  recent
  Journal
  of
 
Organic
 Chemistry
 article
 for
 an
 example
 of
 how
 to
 correctly
 format
 in-­‐text
 citations.
 
For
 the
 proper
 format
 of
 your
 references,
 see
 the
 examples
 below.
 If
 you
 don’t
 see
 the
 example
 you
 
need,
 refer
 to
 the
 ACS
 Style
 Guide.
 

Journal
 Article
 Example
 

Kawano,
 R.;
 Osaki,
 T.;
 Sasaki,
 H.;
 Takinoue,
 M.;
 Yoshizawa,
 S.;
 Takeuchi,
 S.
 J.
 Am.
 Chem.
 Soc.
 2011,
 
133,
 8474-­‐8477.
 

Here’s
 a
 breakdown
 of
 the
 information
 contained
 in
 the
 example
 above:
 

1. Authors
 (in
 normal
 font)
 à
 Kawano,
 R.;
 Osaki,
 T.;
 Sasaki,
 H.;
 Takinoue,
 M.;
 Yoshizawa,
 S.;
 
Takeuchi,
 S.
 
 

2. Journal
 (in
 italics)
 à
 J.
 Am.
 Chem.
 Soc.
 

3. Year
 published
 (in
 bold)
 à
 2011
 

4. Volume
 of
 the
 Journal
 (in
 italics)
 à
 133
 

5. Page
 numbers
 (in
 normal
 font)
 à
 8474-­‐8477
 

Book
 Example
 

Lehman,
 J.
 W.
 The
 Student’s
 Lab
 Companion:
 Laboratory
 Techniques
 for
 Organic
 Chemistry,
 2nd
 ed.;
 
Prentice
 Hall:
 Upper
 Saddle
 River,
 NJ,
 2008;
 pp
 120-­‐132.
 

Here’s
 a
 breakdown
 of
 the
 information
 contained
 in
 the
 example
 above:
 

1. Authors
 (in
 normal
 font)
 à
 Lehman,
 J.
 W.
 
 
 

2. Book
 title
 (in
  italics)
 à
 The
 Student’s
 Lab
 Companion:
 Laboratory
 Techniques
 for
 Organic
 
Chemistry
 

3. Edition
 (in
 normal
 font)
 à
 2nd
 ed.
 

4. Name
 of
 publisher
 &
 place
 of
 publication
 (in
 normal
 font)
 à
 Prentice
 Hall:
 Upper
 Saddle
 
River,
 NJ
 

5. Publication
 year
 (in
 normal
 font)
 à
 2008
 

6. Pages
 referenced
 (in
 normal
 font…note
 that
 for
 books
 you
 must
 include
 a
 “pp”
 whereas
 you
 
do
 not
 for
 journals)
 à
 pp
 120-­‐132
 

General
 Website
 Example
 

Hunt,
 I.
 Halogenation
 of
 Alkenes.
 http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch06/ch6-­‐
7.html
 (accessed
 Aug
 14,
 2013).
 

Here’s
 a
 breakdown
 of
 the
 information
 contained
 in
 the
 example
 above:
 

__________________________________________________________________________________________________________________
4
 

1. Authors,
 if
 any
 (in
 normal
 font)
 à
 Hunt,
 I.
 
 
 

2. Title
 of
 Site
 (in
 normal
 font)
 à
 Halogenation
 of
 Alkenes
 

3. URL
 (in
 normal
 font)
 à
 http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch06/ch6-­‐
7.html
 

4. Date
 accessed
 (in
 normal
 font)
 à
 Aug
 14,
 2013
 

Documents
 Retrieved
 from
 Institutional
 or
 Agency
 Website
 Example
 

Solano,
 D.
 M.
 Topic
 4:
 Writing
 an
 Organic
 Chemistry
 Lab
 Report,
 2015.
 Department
 of
 Chemistry
 &
 
Biochemistry
  -­‐
  Organic
  Chemistry
  Lab
  Manual
  |
  California
  State
  University,
  Bakersfield.
 
http://www.csub.edu/chemistry/organic/manual/Topic4_report
 (accessed
 Aug
 17,
 2015).
 

Here’s
 a
 breakdown
 of
 the
 information
 contained
 in
 the
 example
 above:
 

1. Authors,
 if
 any
 (in
 normal
 font)
 à
 Solano,
 D.
 M.
 

2. Title
 of
 Document
 (in
 normal
 font)
 à
 Topic
 4:
 Writing
 an
 Organic
 Chemistry
 Lab
 Report
 

3. Year
 (in
 normal
 font)
 à
 2015
 

4. Title
  of
  Site
  (in
  normal
  font)
  à
  Department
  of
  Chemistry
  &
  Biochemistry
  -­‐
  Organic
 
Chemistry
 Lab
 Manual
 |
 California
 State
 University,
 Bakersfield
 

5. URL
 (in
 normal
 font)
 à
 
http://www.csub.edu/chemistry/organic/manual/Topic4_Report
 

6. Date
 accessed
 (in
 normal
 font)
 à
 Aug
 17,
 2015
 

The
 ACS
 Format
 for
 Reporting
 a
 Compound’s
 Spectral
 and
 Other
 Data
 
Pretend
 you
 are
 reporting
 data
 for
 ethylbenzene.
 Your
 IR
 and
 NMR
 are
 shown
 below:
 

 

__________________________________________________________________________________________________________________
5
 

 
So
 at
 the
 end
 of
 your
 experimental
 section,
 you
 would
 include
 the
 experimental
 data
 like
 this:
 

Clear,
 colorless
 liquid:
 bp
 137-­‐138
 oC;
 IR
 (neat)
 λmax
 3028,
 2967,
 1806,
 1496,
 1453,
 1030,
 746,
 697
 
cm-­‐1;
 1H
 NMR
 (400
 MHz,
 CDCl3)
 δ
 7.44-­‐7.36
 (m,
 2H),
 7.33-­‐7.23
 (m,
 3H),
 2.60
 (q,
 2H),
 1.25
 (t,
 3H).
 

A
 couple
 important
 points:
 

• You
 don’t
 have
 to
 report
 every
 single
 IR
 peak,
 just
 a
 few
 of
 the
 big
 and/or
 important
 ones.
 

• If
 you
 took
 your
 1H
 NMR
 in
 DMSO
 rather
 than
 chloroform,
 replace
 the
 “CDCl3”
 with
 “DMSO-­‐
d6”.
 

• Be
 sure
 to
 note
 the
 frequency
 of
 the
 NMR
 machine
 that
 you
 used
 (for
 example,
 60
 MHz
 or
 
400
 MHz).
 Also
 note
 that
 the
 frequency
 is
 different
 for
 13C
 NMR.
 

Here’s
 one
 more
 example.
 This
 includes
 the
 IR
 and
 1H
 NMR
 of
 benzoic
 acid:
 

 

__________________________________________________________________________________________________________________
6
 

 
White
 crystalline
 solid:
 mp
 120-­‐122
  oC
 (corrected);
  IR
 (neat)
 λmax
 3071
 (br),
 1696,
 1417,
 1319,
 
1288
 cm-­‐1;
 1H
 NMR
 (60
 MHz,
 CDCl3)
 δ
 12.09
 (br
 s,
 1H),
 8.27-­‐7.97
 (m,
 2H),
 7.77-­‐7.30
 (m,
 3H).
 

Note
 that
 the
 broad
 carboxylic
 acid
 O-­‐H
 stretch
 on
 the
 IR
 has
 a
 “br”
 next
 to
 it
 to
 indicate
 how
 broad
 
it
 is.
 Also,
 the
 proton
 from
 the
 CO2H
 (at
 12
 ppm)
 is
 broader
 than
 normal,
 and
 this
 is
 also
 indicated.
 

Plagiarism
 (and
 How
 to
 Avoid
 It)
 
When
  you
  use
  someone
  else’s
  words,
  ideas,
  and/or
  other
  material
  (such
  as
  images)
  without
 
identifying
  them
  as
  a
  source,
  you
  are
  committing
  a
  form
  of
  academic
  dishonesty
  known
  as
 
plagiarism.
 If
 you
 are
 caught
 committing
 plagiarism,
 you
 will
 be
 reported
 to
 the
 Office
 of
 Student
 
Rights
 and
 Responsibilities
 and
 receive
 a
 grade
 penalty
 (which
 could
 be
 as
 severe
 as
 an
 ‘F’
 for
 the
 
entire
 course),
 so
 it
 is
 in
 your
 best
 interest
 to
 avoid
 plagiarism.
 

The
 first
 step
 to
 avoiding
 plagiarism
 is
 to
 make
 sure
 to
 cite
 all
 sources
 used
 whether
 they
 be
 a
 
textbook,
 journal
 article,
 website,
 or
 other
 source
 (see
 the
 previous
 section
 on
 “The
 ACS
 Format
 for
 
Citing
 and
 Listing
 References”
 for
 the
 proper
 way
 to
 do
 this).
 Keep
 in
 mind
 that
 even
 if
 the
 words
 
are
 your
 own,
 but
 the
 idea
 is
 not,
 you
 must
 cite
 the
 source
 where
 the
 idea
 came
 from.
 Next,
 always
 
be
 sure
 to
 explain
 what
 you
 read
 from
 the
 source
 in
 your
 own
 words.
 In
 the
 rare
 event
 that
 you
 
must
 quote
 the
 source
 directly,
 be
 sure
 to
 use
 quotations.
 (Keep
 in
 mind
 that
 quotes
 are
 generally
 
not
 considered
 acceptable
 in
 scientific
 papers
 and
 you
 will
 usually
 get
 marked
 down
 if
 you
 do
 this
 
in
 a
 lab
 report.)
 Further,
 do
 not
 use
 any
 images
 that
 you
 can
 make
 yourself
 in
 ChemDraw.
 You
 do
 
not
 have
 to
 cite
 ChemDraw
 if
 you
 make
 an
 image
 in
 ChemDraw.
 (You
 wouldn’t
 cite
 Microsoft
 Word
 
just
  because
  you
  used
  it
  to
  write
  your
  report.)
  If
  you
  find
  an
  image
  you
  need
  to
  use
  that
  is
 
impossible
 to
 duplicate
 on
 your
 own,
 be
 sure
 to
 make
 it
 clear
 that
 the
 image
 is
 not
 your
 own.
 

Finally,
  take
  care
  that
  you
  do
  not
  plagiarize
  from
  other
  students.
  This
  means
  that
  if
  you
  work
 
together,
 you
 must
 make
 sure
 that
 you
 both
 use
 your
 own
 words
 and
 ChemDraw
 images
 (i.e.,
 do
 not
 
copy).
 

__________________________________________________________________________________________________________________
7
 

References
 &
 Additional
 Resources
 
1. Lehman,
 J.
 W.
 The
 Student’s
 Lab
 Companion:
 Laboratory
 Techniques
 for
 Organic
 Chemistry,
 2nd
 

ed.;
 Prentice
 Hall:
 Upper
 Saddle
 River,
 NJ,
 2008;
 pp
 36-­‐37.
 

2. The
 ACS
 Style
 Guide
 [Online];
 Coghill,
 A.
 M,
 Garson,
 L.
 R.,
 Eds.;
 
 American
 Chemical
 Society:
 
Washington,
 DC,
 2006.
 http://pubs.acs.org/isbn/9780841239999
 (accessed
 Aug
 18,
 2015).
 

3. Spectral
 Database
 for
 Organic
 Compounds
 SDBS.
 National
 Institute
 of
 Advanced
 Industrial
 
Science
 and
 Technology
 (AIST).
 http://sdbs.db.aist.go.jp
 (accessed
 Sept
 13,
 2015).