Full Lab Report #8
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Transcript of Full Lab Report #8
Department of Chemistry
Virginia Commonwealth University
CHEZ 302 – Organic Chemistry II Lab
Experiment #8: Synthesis of an Ester
Submitted by: Joseph Thomas Morrison ___________________________
Start date: March 28th, 2013 Signature
Completion date: March 28th, 2013
Submission date: April 4th, 2013
Pages in lab notebook: 21-23
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Table of Contents
1. Title Page…………………………...……………………………………
2. Table of Contents………………………………………………………...
3. Objective……………………………………………………………........
4. Synthetic Equations…………………………………………..………….
5. Physical Properties……………………………………...……………….
6. Experimental Procedure…………………...…………………………….
7. Calculations……………………………………………………………...
8. Results…………………………………………………………………...
9. Discussion……………………………………………………………….
10. References…………………………………...…………………………..
11. Attachments
IR Spectrum of Product (Methyl Salicylate)
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Objective
The objective of this experiment was to form methyl salicylate from salicylic acid and
methanol in the presence of an acid catalyst through a facilitated esterfication chemical reaction
using the techniques of heating under reflux, separation, gravity filtration, and rotary evaporation
while driving the reaction equilibrium toward the products by using an excess of methanol. An
additional objective of this experiment was to validate the product (methyl salicylate) using the
techniques of percent yield calculation and IR (infrared spectroscopy).
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Synthetic Equations
Theoretical Yield of Methyl Salicylate
(mols of Limiting Reagent )( molsof Methl Salicylatemols of Limiting Reagent )( gramsof Methyl Salicylatemol of Methyl Salicylate )=TheoreticalYield of Methyl Salicylate
Percent Yield of Methyl Salicylate
[ Actual Yield of Methyl SalicylateTheoreticalYield of Methyl Salicylate ]×100 %=Percent Yield of Methyl Salicylate
Overall Reaction of Salicylic Acid and Methanol to Methyl Salicylate
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Physical Properties
Note: All physical properties of liquids and solids from this experiment were obtained from
Sigma Aldrich. [1]
Liquids
Name: Methanol
Molecular Weight: 32.04 g/mol
Boiling Point: 64.7 °C
Density: 0.7918 g/mL
Hazards: Flammable and toxic.
Structure:
Name: Sulfuric Acid
Molecular Weight: 98.08 g/mol
Boiling Point: 337 °C
Density: 1.84 g/mL
Hazards: Corrosive and toxic.
Structure:
Name: Methylene Chloride
Molecular Weight: 84.93 g/mol
Boiling Point: 39.6 °C
1[] Sigma-Aldrich. N.p., n.d. Web. 13 Mar. 2013. <.http://www.sigmaaldrich.com>.
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Density: 1.33 g/mL
Hazards: Carcinogen.
Structure:
Name: Sodium Bicarbonate
Molecular Weight: 84.01 g/mol
Boiling Point: 851 °C
Density: 2.20 g/mL
Hazards: Irritant.
Structure:
Name: Methyl Salicylate
Molecular Weight: 152.15 g/mol
Boiling Point: 220-224 °C
Density: 1.174 g/mL
Hazards: Toxic by ingestion.
Structure:
Solids
Name: Salicylic Acid
Molecular Weight: 138.12 g/mol
Melting Point: 159 °C
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Hazards: Toxic by ingestion.
Structure:
Name: Sodium Sulfate (Anhydrous)
Molecular Weight: 142.04 g/mol
Melting Point: 884 °C
Hazards: Irritant.
Structure:
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Experimental Procedure
To a 50 mL round-bottom flask, 4.9 grams of salicylic acid (4.9 grams, 0.035 mols) was
added. 12.5 mL of methanol (9.9 grams, 0.309 mols) was added to the flask, and the flask was
swirled to dissolve the solid. When the solid was dissolved, 5.0 mL of concentrated sulfuric
acid (9.2 grams, 0.094 mols) was slowly added with swirling. A white solid formed in the
flask. A reflux condenser was attached and the mixture was heated at reflux for 45 minutes. A
layer of oil formed on the top of the refluxing mixture. The mixture was swirled occasionally
during the reflux period. The reaction mixture was allowed to cool to room temperature. 10
mL of ICE water was added to the mixture and the contents of the flask were transferred to a
separatory funnel. The product (methyl salicylate) was extracted into two 15 mL portions of
methylene chloride (19.9 grams, 0.235 mols). The mixture was shaken gently during the
extractions and washings. The combined methylene chloride extracts were washed with 15
mL of water, followed by 15 mL of 5 % aqueous sodium bicarbonate solution (33.3 grams,
0.393 mols). The organic layer was dried over sodium sulfate and then gravity filtered into a
pre-weighed 100 mL round-bottom flask (39.5 grams) and the solvent was evaporated using a
rotary evaporator. The product was an oil – and care was taken not to evaporate past the point
where the solvent was gone, or evaporation (and, therefore, loss) of the product occurred. The
product was weighed and the percent yield was determined. An IR and an NMR were run on
the product.
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Calculations
Theoretical Yield of Methyl Salicylate
( 4.9 gSalicylic Acid
( 138.12g Salicylic Acid1mol Salicylic Acid ) )(
1molMethyl Salicylate1mol Salicylic Acid )( 152.15 gMethyl Salicylate
1molMethyl Salicylate )=5.40gMethyl Salicylate
Percent Yield of Methyl Salicylate
[ 5.03 gMethyl Salicylate5.40 gMethyl Salicylate ]×100%=93.15 %
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Results
IR Results
The IR spectrum showed peaks at 3100 cm-1, 1640 cm-1, 1500 cm-1, and 1050 cm-1, which
represented a C=CH aromatic stretch, C=O amide, C=C aromatic, and a C-O ether respectively.
NMR Results
The NMR spectrum showed a 2H doublet at7.4 ppm, 2H doublet at 6.8 ppm, 2H quartet at 4.0
ppm, 3H singlet at 2.1 ppm, and a 3H triplet at 1.4 quartet at 1.4 ppm, which represented
hydrogen(s) attached to a aromatic group (CH), aromatic group (CH), OC6H5 group (CH2),
CONR2 group (CH3), and a CH2R group (CH3) respectively.
Percent Yield
The percent yield of phenacetin from the experiment was determined to be 35.39 %
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Discussion
The objective of this experiment was to form phenacetin from acetaminophen through a
facilitated Williamson ether synthesis chemical reaction using the techniques of heating under
reflux, vacuum filtration and recrystallization incorporating a mixed-solvent system. An
additional objective of this experiment was to validate the product (phenacetin) using the
techniques of melting point determination, percent yield calculation, IR (infrared spectroscopy),
and NMR (nuclear magnetic resonance). The melting point of the product was determined to be
109-110 °C which was significantly lower than the literature melting point of phenacetin (134-
136 °C) which supported the hypothesis that impurities were present in the product. Phenacetin
was successfully formed during this experiment with a determined percent yield of 35.39 %. As
stated earlier in this report, the IR spectrum showed peaks at 3100 cm-1, 1640 cm-1, 1500 cm-1,
and 1050 cm-1, which represented a C=CH aromatic stretch, C=O amide, C=C aromatic, and a
C-O ether respectively. These results were representative of the results expected from the IR
spectrum of pure phenacetin. As stated earlier in this report, the NMR spectrum showed a 2H
doublet at7.4 ppm, 2H doublet at 6.8 ppm, 2H quartet at 4.0 ppm, 3H singlet at 2.1 ppm, and a
3H triplet at 1.4 quartet at 1.4 ppm, which represented hydrogen(s) attached to a aromatic group
(CH), aromatic group (CH), OC6H5 group (CH2), CONR2 group (CH3), and a CH2R group (CH3)
respectively. These results were representative of the results expected from the NMR spectrum
of pure phenacetin with one exception. It was expected that there would be a 1H singlet at 8 from
the amide N-H, however this peak was not observed in the NMR spectrum which indicated that
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human error or equipment error was a possible factor in the non-existent peak. In this
experiment, p-acetamidophenol (acetaminophen), a phenol, was be de-protonated by sodium
methoxide. The resulting phenoxide ion then reacted with bromoethane (ethyl bromide) to give
phenacetin (p-ethoxyacetanilide). Because of the nature of a Williamson ether synthesis, adding
equimolar amounts of acetaminophen and sodium methoxide was crucial in preventing unwanted
side reactions and to obtain the pure phenacetin product. The results of the Williamson ether
synthesis showed that human error was probable due to the significantly low melting point (109-
110 °C) and the significantly low percent yield of phenacetin (35.39 %). Of which, human error
in the form of the addition of non-equimolar amounts of acetaminophen and sodium methoxide
mistakenly was probable. The results of the Williamson ether synthesis also showed that
equipment error was probable due to the missing peak in the NMR spectrum (amide N-H) but the
represented C=O amide peak in the IR spectrum. Overall, phenacetin was obtained from the
experiment using the techniques of heating under reflux, vacuum filtration and recrystallization
incorporating a mixed-solvent system. The product was also validated using the techniques of
melting point determination, percent yield calculation, IR (infrared spectroscopy), and NMR
(nuclear magnetic resonance). Therefore, the experiment’s objectives were successfully
completed.
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References
[] Sigma-Aldrich. N.p., n.d. Web. 13 Mar. 2013. <.http://www.sigmaaldrich.com>.
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