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Lab Report for Nitration of Methyl Benzoate
Student Name
Course
Instructor
Institution Affiliation
Date
Table of Contents
1.Introduction …………………………………………………………………………………………………………….. 3
2.Objectives of the Experiment…………………………………………………………………………………….. 3
3.Analysis of Product ………………………………………………………………………………………………….. 3
4.Conceptual Information ……………………………………………………………………………………………. 3
5.General EAS Mechanism ………………………………………………………………………………………….. 4
6.Factors affecting the Expected Outcome …………………………………………………………………….. 4
7.Apparatus and Reagents ……………………………………………………………………………………………. 5
8.Lab Procedure …………………………………………………………………………………………………………. 6
9.Data ……………………………………………………………………………………………………………………….. 7
10.Discussion …………………………………………………………………………………………………………….. 8
11.Future Improvements ……………………………………………………………………………………………… 9
12. Conclusion …………………………………………………………………………………………………………. 10
Lab Report for Nitration of Methyl Benzoate
1.Introduction
The experiment was carried out so as to determine the substitution of NO2 group for one of
the hydrogen atoms on a benzene ring. The process is an electrophilic aromatic substitution
reaction. The nitronium ion generated by the interaction of concentrated nitric and sulfuric
acid is the electrophile.
2.Objectives of the Experiment
This experiment was aimed at performing an electrophilic aromatic substitution by nitrating
methyl benzoate. The process would produce methyl 3- nitrobenzoate and show that the
reaction indulged regioselectivity.
3.Analysis of Product
The identify and confirm the purity of the obtained product after nitration, the following
methods were to be used:
•
The melting point was to be determined and this involved the comparison of values
for methyl 3-nitrobenzoate with the literature values.
•
Thin layer of chromatography (TLC) was to be run so as to access the product purity
and identify any potential side products that would have been present.
4.Conceptual Information
The following concepts were used as bases for the experiment:
Regioselectivity: The preferential substitution at the three positions of the aromatic ring due
to the electron-withdrawing effect of the ester group involved which activated the meta
positions.
Directing groups: The ester group acted as a meta-directing group which influenced the
electrophile (NO2+) to attack the 3-position.
Induction: This involved the electron-withdrawing nature of the ester group (-C(=O) O-)
which withdraw the electron density from the aromatic ring. This makes the meta position
more susceptible to electrophilic attack.
Electrophilic Aromatic Substitution (EAS) mechanism: The multi-step process that involved
the protonation of Nitric acid, nitration of aromatic ring, and deprotonation to restore
aromaticity.
5.General EAS Mechanism
1. The protonation of Nitric acid: H2SO4 protonates HNO3 forming the Nitronium ion
(NO2+).
2. The nitration of Aromatic ring: NO2+ attacks the activated meta position of the
aromatic ring forming a σ-complex.
3. Deprotonation: A proton is removed from the σ-complex, restoring aromaticity and
general methyl 3-nitrobenzoate.
6.Factors affecting the Expected Outcome
1. The reaction temperature
Increase in temperature increases the side reactions and thus affects the yield by
decreasing it.
2. Reaction time
Having insufficient time may lead to incomplete conversions, while excessive time
can lead to over-nitration.
3. Purity of agents
Impurities can intervene with the reaction and affects the amount of yield.
4. Stoichiometry
The use of correct ratios of reactants is crucial for efficient product formation.
7.Apparatus and Reagents
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4ml conical vial and 2ml conical vial
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Spin vein
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2 small test tubes
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1 beaker 250 ml
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1 beaker 50 ml
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Micro pipets and tips
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Ice baths
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Spatulas
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Hirsch funnels- drawers
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Side-arm flasks
•
Hot plate
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2 Test tube holders
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Capillary tubes
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Glass Pasteur pipets
•
2 ml gradual pipet *2
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Methyl benzoate
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Sulfuric acid
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Nitric acid
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Methanol
8.Lab Procedure
2 ml graduated pipet was used to dispense 0.6ml of concentrated sulfuric acid in the 4 ml
conical vial and cooled to 0 degrees Celsius. 0.3 g of methyl benzoate was added using the
micro pipet set and then set to 280 microliters. The mixture was cooled for 10 minutes in the
ice bath. 0.2 ml of nitric acid was dispensed in the 2 ml conical vial using the 2 ml graduated
pipet. 0.2 ml of sulfuric acid was added to the nitric acid in the vial.
Spin vein was weighed and added to the sulfuric acid and methyl benzoate mixture while it
was in the ice bath. The ice bath was then placed on the strip plate. The mixture of 0.2 ml
concentrated sulfuric acid and 0.2 ml of fresh concentrated nitric acid was added to the
sulfuric/methyl benzoate mixture using the Pasteur pipette with the stir plate on. The reaction
mixture was kept in the ice and stirred.
After the addition of all the nitric acid and sulfuric acid mixture, the mixture was warmed to
room temperature and after 15 minutes it was poured on to 2.5 grams of ice in a small beaker.
The beaker was placed in the ice bath and the ice in the small beaker allowed to melt slowly
while stirring occasionally with the capillary tube. The solid product was isolated by filtration
when completely melted using the Hirsch funnel and a 25 ml side arm filter flask.
The product was washed well with water and then with few drops of ice-cold 50% methanol.
The reason for washing with ice cold methanol is to avoid losing the product. A small crude
sample was saved for melting purposes in a capillary tube and for thin-layer chromatography
analysis.
The remainder was weighed and recrystallized using the mixed solvent technique which was
water and ethanol. Minimal hot solvent mixture was added drop by drop until the solute was
dissolved. The slow cooling was supposed to produce large crystals with a melting point of
78 degrees Celsius. Two small test tubes were placed in hot bath keeping water around 75-80
degrees Celsius. One of the tubes was for the 50/50 solvent, while the other was for the lab
product.
9.Data
Mass of vial +H2SO4 = 27.011 g
Mass of tube = 8.697 g
Mass of methyl benzoate = 0.393
Tube + methyl benzoate= 9.09 g
Mass of vial + HNO3 + H2SO4 = 20.883 g
Weight of spin vein = 0.697 g
Mass of ice = 2.55 g
Mass of sample = 26.869 g – 26.631 g = 0.238 g
% of recrystallized product = 0.238g/26.869g*100
=0.885%
Mass of crude = 21.873 g
Mass of all products = 22.107 g
Mass of product= 0.234 g
% of mass product = 0.234g/22.107g *100
=1.058%
Melting point 1 = 77.6 degrees Celsius
Melting point 2 = 78.4 degrees Celsius
Average melting point = 78 degrees Celsius
Parameter
Value
Mass of crude product
0.238 g
Mass of recrystallized product
0.234 g
Melting point of crude product
77.2 ᶱC
Melting point of recrystallized product
78.0 ᶱC
10.Discussion
The objective of the experiment was to characterize and synthesize methyl 3- nitrobenzoate
through the nitration of methyl benzoate. The analysis involved the determination of the
melting point of the product and the optional TLC of the lab works. Having an understanding
of EAS mechanisms and the influences of the directing groups was crucial.
Regioselectivity and Product Position: The meta position withdrawing effect was activated by
the easter group`s electron. This directed the nitration in the 3-position of the aromatic ring.
Steric hinderance could be one of the factors that attributed to influence of regioselectivity to
a lesser extent.
Product Loss and Yield Improvement: Product loss would have been potentially influenced by
the incomplete reactions taking place. Inefficient isolation and purification process also
attributed to product loss. Implementations could be done in various areas so as to improve the
yield and reduce the product loss. This could be done by : optimizing the reaction conditions
which are influenced by time and temperature, ensuring there is proper mixing of the reagents
at the required steps, minimizing the product loss during the isolation process and improving
the yield.
Melting Point and Purity: The melting point of the crude was (77.2ᶱC) and the recrystallization
melting point was (78ᶱC) . These values closely matched with the literature values which were
(78-80ᶱC) for methyl 3-nitrobenzoate. This illustrates that the product was pure in which the
recrystallization process further purified the product.
Recrystallization process: It involved the dissolving of impurities from the hot solvent mixture
more readily than the product would have been dissolved. The slow cooling process enhanced
the purified product to be crystallized out of the solution. The recrystallized methyl 3nitrobenzoate was yielded by the processes of filtration and drying.
11.Future Improvements
1. Optimization of the solvent system should be done for recrystallization.
Having a number of alternatives to play part in the solvent mixtures or the
recrystallization technique could further enhance the chances of purity for the final
product.
2. Controlling the reaction conditions more precisely.
Temperature should be controlled by using a constant-temperature bath instead of
using the ice bath. This could ensure better control over the reaction temperature and
potentially improve the yield and consistency in melting point values.
3. Reaction progress monitorization.
The use of the thin-layer chromatography (TLC) analysis at different time intervals
could help in determining the optimal reaction time and minimize chances of overnitration.
12. Conclusion
The nitration of methyl benzoate successfully yielded and synthesized methyl 3-nirobenzoate.
The experiment`s analysis provided full proof of the identity and purity of the product formed
by the close ranges of the experiment`s melting point and literature`s melting point. The
experiment also showed the electrophilic aromatic substitution and the influence of directing
groups in 3-phase. Having addressed the sources of product loss and yield improvement
together with future improvements on the same, any experiment carried out in future could be
more precise.
Nitration of Methyl
Benzoate
K. L. Williamson, Macroscale and Microscale Organic Experiments,
2nd Ed. 1994, Houghton Mifflin, Boston . p423 Revised 10/9/00
Important Info.
•
•
•
•
Nitration: substitution of an NO2 group for one of the hydrogen
atoms on a benzene ring. The nitration of methyl benzoate is a typical
electrophilic aromatic substitution reaction. The electrophile is the
nitronium ion generated by the interaction of concentrated nitric and
sulfuric acids.
Objective: In this experiment, the student will perform an
electrophilic aromatic substitution by nitrating methyl benzoate,
demonstrating the reaction’s regioselectivity and producing methyl 3nitrobenzoate.
Mechanism Overview: The solvent sulfuric acid protonates the
methyl benzoate. The resonance stabilized arenium ion intermediate
then transfers a proton to the basic bisulfate ion to give methyl 3nitrobenzoate.
Directing Effects: The ester group is a meta director and a deactivator
of the benzene ring. It is much easier to nitrate a molecule such as
phenol, where the hydroxyl group is an ortho-para director and an
activator of the benzene ring.
Generic Nitration Mechanism
Specific Mechanism
https://www.youtube.com/watch?v=pw2aknukuFk
•
The carbonyl group withdraws electron density from the ring
deactivating it towards electrophilic substitution. However,
the 3-position is less deactivated towards nitration than the
other positions owing to the relative stability of the different
intermediates. Therefore the reaction is regioselective for
nitration at the 3-position.
Materials/Chemicals Used
•
Methyl Benzoate – Use caution when handling, as it is hazardous in the cases of
skin contact, eye contact, ingestion, and inhalation
•
Sulfuric Acid – Very hazardous in case of skin contact (corrosive, irritant,
permeator), of eye contact (irritant, corrosive), of ingestion, of inhalation.
Liquid or spray mist may produce tissue damage particularly on mucous
membranes of eyes, mouth and respiratory tract.
•
Nitric Acid – Very hazardous in case of skin contact (corrosive, irritant,
permeator), of eye contact (irritant, corrosive), of ingestion, of inhalation.
Liquid or spray mist may produce tissue damage particularly on mucous
membranes of eyes, mouth and respiratory tract.
•
Methanol – Hazardous in case of skin contact (irritant), of eye contact (irritant),
of ingestion, of inhalation. Slightly hazardous in case of skin contact
(permeator). Severe over-exposure can result in death. The substance is toxic
to eyes. The substance may be toxic to blood, kidneys, liver, brain, peripheral
nervous system, upper respiratory tract, skin, central nervous system (CNS),
optic nerve. Repeated or prolonged exposure to the substance can produce
target organs damage.
Equipment
•
•
•
•
•
•
•
•
•
•
•
•
•
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4 mL conical vial and 2 mL conical vial
spin vein
Small test tubes x2
Beakers – 1x 250 mL and 1x 50 ml
Micro Pipet and tips
Ice baths
Spatulas
Hirsch funnels – drawers
Side-arm flasks
Hot plate
Test tube holder x2
Capillary tubes
Glass Pasteur Pipets
2 mL graduated pipet x2
Procedure
1.
Use 2 mL graduated pipet to dispense 0.6 mL of concentrated sulfuric acid in
the 4 mL conical vial, cool to 0 °C in, then add to it 0.30 g of methyl benzoate
using a micro pipet set to 280 microliters. Cool this mixture for 10 minutes in
ice bath.
2.
In the 2 mL conical vial, dispense .2 mL of Nitric Acid using a 2 mL graduated
pipet, and then add .2 mL of sulfuric acid to nitric acid in vial.
3.
Weigh and add spin vein to the sulfuric acid and methyl benzoate mixture
while it’s in the ice bath, and place the ice bath on stir plate. Using a Pasteur
pipette, add the mixture of 0.2 mL of concentrated sulfuric acid and 0.2 mL of
fresh concentrated nitric acid to the sulfuric/methyl benzoate mixture WITH
THE STIR PLATE ON . Keep the reaction mixture in ice AND STIRRING.
4.
After all the nitric acid and sulfuric acid mixture has been added, warm the
mixture to room temperature, and after 15 min., pour it onto 2.5 g (a small
amount) of ice in a small beaker. Place small beaker in ice bath and let ice in
small beaker melt slowly, stirring occasionally with a capillary tube.
Procedure
5.
Once completely melted, isolate the solid product by suction filtration using
the Hirsch funnel and a 25 mL sidearm filter flask.
6.
Wash the product well with water and then with a few drops of ice-cold 50%
methanol.
O
If the wash methanol is not ice-cold, product can be lost in this washing step.
7.
Save a small crude sample in capillary tube for melting-point determination
and analysis by thin-layer chromatography if you choose to do so.
8.
The remainder is weighed and recrystallized using the mixed solvent
technique (water and methanol). Add minimal hot solvent mixture, drop by
drop, until solute is dissolved (It is important to have a saturated solution
while hot). Slow cooling should produce large crystals, with a melting point of
78 °C (the crude material can be obtained in about 80% yield with a melting
point of 74 to 76 °C).
O
9.
Place two small test tubes in hot bath (keep water around 75-80 degrees). One tube is for the 50/50
solvent, and the other is for your product
Perform TLC on recrystallized product (Extra Credit: +5 points on lab report)
O
Data and concept must be addressed in lab report to receive full credit
Clean Up/Waste
• The product will be collected for further
analysis in the Claisen fume hood
• A labeled waste container will be provided in
the Cope fume hood for all liquid waste.
✓ (excess sulfuric acid, nitric acid, and filtrates from collection and
recrystallization)
Nitration of Methyl Benzoate Report Rubric
Write in passive voice (no personal pronouns: we, you, I, they, etc.)
Pre-lab: 15% (submitted through Turnitin). Handwritten in ink
Introduction: 25 points
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•
•
•
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Expected outcome and goal – 5 points
How to analyze your product – 3 points
Explain and define all conceptual info (regioselectivity, directing groups, induction, etc.) – 6 points
Describe the general EAS mechanism – 8 points
Factors that affect the expected outcome – 3 points
o (What COULD affect your outcome?)
Experimental: 5 points
•
•
•
Citation of lab text – 1 point
Student lab journal reference including page numbers – 1 point
Explain lab procedure – 3 points
o
o
In depth discussion of the nitration procedure
Brief mention of recrystallization and melting procedure (include solvent used and purposes)
Data: 15 points
-“Sandwich data” (paragraphs introducing and explaining data)
-Organize data in a table
• Mass of crude and recrystallized (if necessary) product – 3 points
• Melting point of crude and recrystallized (if necessary) product – 3 points
• Theoretical yield of product (yes… you need to use stoichiometry, limiting reagent, and
molecular weights) – 6 points
o Make sure to show this work! If you don’t, we will take points off!
•
Percent yield of product – 3 points
Discussion: 25 points
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•
Briefly summarize the introduction – 3 points
Explain the regioselectivity based on the directing groups – 5 points
o
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What position did the EAS take place at? – check chapter 15 in lab manual
▪ Hint… go deeper than what the slides say 🙂
Determine/discuss how much product was lost – 6 points
Possible ways you could have increased your yield – 2 points
Compare melting points to the literature value – 2 points
Explain relative purity using melting point concepts – 3 points
Recrystallization process (solvent used, boiling out, etc.). – 2 points
What you would do differently if you were to repeat the experiment in the future – 2 points
Lab Report (70 points) + Prelab (15 points) + Post lab questions (15 points) = 100
ZX
Lab Report for Nitration of Methyl Benzoate
Introduction
Expected Outcome and Goal
This experiment aimed to synthesize methyl 3-nitrobenzoate through the nitration of
methyl benzoate. By studying this electrophilic aromatic substitution (EAS) reaction, we
observed the influence of directing groups on product regioselectivity.
Analysis of Product
The identity and purity of the obtained product were confirmed through:
•
Melting point determination: Comparison with literature values for methyl 3-nitrobenzoate.
•
Thin-layer chromatography (TLC): Assessment of product purity and identification of
potential side products (optional).
Conceptual Information
•
Regioselectivity: Preferential substitution at the 3-position of the aromatic ring due to the
electron-withdrawing effect of the ester group, activating the meta position.
ZX
•
Directing Groups: The ester group acted as a meta-directing group, influencing the
electrophile (NO2+) to attack the 3-position.
•
Induction: The electron-withdrawing nature of the ester group (-C(=O)O-) withdraws
electron density from the aromatic ring, making the meta position more susceptible to
electrophilic attack.
•
Electrophilic Aromatic Substitution (EAS) Mechanism: The multi-step process involved
protonation of nitric acid, nitration of the aromatic ring, and deprotonation to restore
aromaticity.
General EAS Mechanism
1. Protonation of Nitric Acid: H2SO4 protonates HNO3, forming the nitronium ion (NO2+).
2. Nitration of Aromatic Ring: NO2+ attacks the activated meta position of the aromatic
ring, forming a σ-complex.
3. Deprotonation: A proton is removed from the σ-complex, restoring aromaticity and
generating methyl 3-nitrobenzoate.
Factors Affecting the Expected Outcome
•
Reaction temperature: Higher temperatures can increase side reactions and decrease yield.
•
Reaction time: Insufficient time may lead to incomplete conversion, while excessive time can
promote over-nitration.
•
Purity of reagents: Impurities can interfere with the reaction and affect yield.
•
Stoichiometry: Using the correct ratio of reactants is crucial for efficient product formation.
Experimental
Lab Procedure
ZX
1. Use 2mL. graduated pipet to dispense 0.6mL of concentrated H2804 in the 4mL conical vial,
cool to Ic in, then add to it 0.30g of methyl benzoate using a micro pipet this mixture for 10
minutes in ice bath set to 280 microliters. Cool the mixture for 10mins in ice bath.
Mass of vial + H2504 27.011g
Tube + methyl benzoate 9.09 g
Mass of tube 8.697 g
Mass of methyl benzoate 0.393g
2. In the 2ml conical vial, dispense. 2mL of HNO3 using a 2mL graduated pipet, and then add 2
mL of H2SO4 to HNO3 in vial.
Mass of vail + HNO3 + H2SO4 = 20.883g
3. Weigh and add spin vein to the H2SO4 and methyl benzoate mixture while it’s in the ice bath,
and place the ice bath on stir plate. Using a Pasteur pipette, add the mixture of 0.2 mL of
Concentrated H2SO4 and 0.2 mL of fresh concentrated HNO3 to the sulfuric / methyl benzoate
mixture WITH THE STIR PLATE ON keep the reaction mixture in ice AND STIRRING
Weight of spin vein = 0.697g
4. After all the HNO3 and H2SO4 mixture has been added, Warm the mixture to room
temperature, and after 15 mins pour it onto 2.5g (a small amount) of ice in a small beaker. Place
small beaker melt slowly, stirring occasionally with a capillary tube
Mass of ice 2.55g
ZX
5. Once completely melted, isolate the solid product by suction filtration using the Hirsch funnel
and a 25 mL sidearm filter flask
6. Wash the product well with water and then with a few drops of ice-cold 50% methanol
Mass of sample : 26.869g -26 631g =0.238g
7. Save a small crude sample in capillary tube for melting-point determination and analysis by
thin-layer chromatography if you choose to do so. 77.2℃
8. The remainder is weighed and recrystallized using the mixed Solvent technique (water and
methanol). Add minimal hot solvent mixture, drop by drop until solute is dissolved (it is
important to have a saturated solution while hot). Slow cooling should produce large crystals,
with a melting point of 78°C (the crude material can be obtained in about 80% yield with melting
point of 74 to 76°C).
Mass of = 21.873g
Mass of all = 22.107g
Mass of product=0.234g
Melting point 1 = 77.6℃
Melting Point 2 = 78.4°C
9. Perform TLC on recrystallized product.
Avenge Melting Point = 78°C
Data
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Parameter
Value
Mass of crude product
0.238 g
Mass of recrystallized product
0.234 g
Melting point of crude product
77.2°C
Melting point of recrystallized product
78°C
Discussion
This experiment aimed to synthesize and characterize methyl 3-nitrobenzoate through the
nitration of methyl benzoate. The product analysis involved melting point determination and
optional TLC. Understanding EAS mechanisms and the influence of directing groups was
crucial.
Regioselectivity and Product Position
The ester group’s electron-withdrawing effect activated the meta position, directing the
nitration to the 3-position of the aromatic ring. Other factors like steric hindrance could also
influence regioselectivity to a lesser extent.
Product Loss and Yield Improvement
Potential product losses could occur during incomplete reaction, inefficient isolation, and
purification steps. To improve yield, optimizing reaction conditions (temperature, time), ensuring
proper mixing, and minimizing product loss during isolation could be implemented.
Melting Point and Purity
ZX
The melting points of the crude (77.2°C) and recrystallized (78°C) product closely
matched the literature value for methyl 3-nitrobenzoate (78-80°C). This indicates a relatively
pure product, with the recrystallization further enhancing its purity.
Recrystallization Process
The hot solvent mixture dissolved impurities more readily than the product. Upon slow
cooling, the purified product crystallized out of the solution. Filtration and drying yielded the
recrystallized methyl 3-nitrobenzoate.
Future Improvements
•
Monitoring reaction progress: Implementing thin-layer chromatography (TLC) at different
time intervals could help determine the optimal reaction time and minimize over-nitration.
•
Controlling temperature more precisely: Using a constant-temperature bath instead of an ice
bath could ensure better control over the reaction temperature and potentially improve yield
and consistency.
•
Optimizing solvent system for recrystallization: Exploring alternative solvent mixtures or
recrystallization techniques could further enhance the purity of the final product.
Conclusion
This experiment successfully synthesized methyl 3-nitrobenzoate through the nitration of
methyl benzoate. Analysis by melting point determination confirmed the product’s identity and
purity. The experiment served as a valuable demonstration of electrophilic aromatic substitution
and the influence of directing groups. Addressing potential product losses and exploring
optimization techniques could further improve the yield and efficiency of the reaction in future
attempts.

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