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EXAMINATION PAPER
Examination Session Year Exam Code
May/June 2024 CHEM3127
Title
Practical Chemistry 3 – Organic (2022-23 syllabus)
Release date and time 22 May 2024 9:30
Latest submission date and time 29 May 2024 9:30
Format of exam Open-book, take-home exam
Nominal duration 6 hours
Additional material provided COSHH risk assessment template
Form of submission Up to two PDFs of handwritten or typed work or
PDF.
Name your PDF with your Z code and the Exam
Code e.g., Z1234567-CHEM3127.pdf. Write or
type your Z code and the Exam Code on the irst
page of your PDF(s).
Submission method Send your PDF(s) by email to
chemistry.exams@durham.ac.uk
Instructions to candidates
Answer BOTH questions.
Each question carries 50 marks.
Page 2 of 8 CHEM3127
1. Below is a page from a laboratory course manual. Read the page carefully and then answer all
the questions on the following page. Note that you will not be carrying out this experiment in
the laboratory.
Experiment 1: Selective reduction of p-nitroacetophenone
Set up a reflux apparatus. Place p-nitroacetophenone (2.1 g) in a 250 ml round-bottomed flask together
with iron filings (ca. 2 g) and a magnetic stirrer bar. Add about 50 ml of 2M hydrochloric acid to the mixture
in the flask via the condenser using a Pasteur pipette. Do this carefully and wipe up any spillage
immediately. Heat the mixture in the flask using a boiling water bath for about 1 hour.
Allow the mixture to cool to room temperature. Now you must neutralise the solution of amine salt with
concentrated sodium hydroxide solution. Cool 25 ml of the concentrated (40%) sodium hydroxide solution
provided in an ice bath. Once the reaction mixture has cooled to room temperature cool it further using
an ice bath and add the cooled solution of sodium hydroxide in small portions to the acid solution with
thorough stirring. Make sure the mixture is well stirred after each addition and that the mixture does not
become hot. After the addition of sodium hydroxide check the pH of the mixture. When the mixture is
alkaline filter off the precipitate through a hyflo plug.
Assemble a large Büchner funnel, filter paper and Büchner flask as for a normal suction filtration. Make a
slurry of hyflo in your solvent, which in this case is water. Pour the slurry on to the filter paper with the
suction on to make a pad about 1 cm deep covering all the filter paper. Discard the residual solvent from
the Büchner flask. Now perform suction filtration as normal. Your product will be on the top of the hyflo
in the Büchner funnel. Transfer the hyflo and your crude product into a beaker.
Separate your product from the mixture with hyflo as follows:
Add 30 – 50 ml of ethyl acetate (in which your product dissolves) to the mixture of your crude
product and hyflo and stir it.
Filter the resulting mixture (Büchner filtration) and wash with 30 ml of ethyl acetate.
Place the filtrate in a round bottom flask (no more than 1/3 full).
Remove the solvent from the filtrate using a rotary evaporator.
Recrystallise the residue from water, and then dry your crystals further by placing them in the vacuum
desiccator for 20-30 minutes. Record an IR spectrum of your product.
Prepare your sample for submission.
Page 3 of 8 CHEM3127
(a) Write a step-by-step procedure describing how to recrystallise the crude product from
water.
[12 marks]
(b) Describe how each of the following should be disposed of correctly and safely in the
laboratory:
(i) A small quantity of spilt p-nitroacetophenone (solid);
(ii) 25 ml of 40% sodium hydroxide solution that has been spilt in a fume cupboard;
(iii) A used glass Pasteur pipette;
(iv) Waste solvent from the rotary evaporation collection flask.
[8 marks]
(c) Write an experimental procedure (journal style) for this experiment assuming there were
no deviations from the given procedure. This should include the following:
percentage yield of p-aminoacetophenone produced, assuming the obtained mass
was 1.21 g;
full assignment of the mass spectrum (Figure 1 on the following pages);
full assignment of the 1H NMR spectrum (Figure 2 on the following pages);
full assignment of the 13C NMR spectrum (Figure 3 on the following pages).
[30 marks]
Page 4 of 8 CHEM3127
Figure 1: Electron Ionisation Mass Spectrum of p-aminoacetophenone

Page 5 of 8 CHEM3127
Figure 2: 1H NMR spectrum of p-aminoacetophenone
Page 6 of 8 CHEM3127
Figure 3: 13C NMR spectrum of p-aminoacetophenone
Page 7 of 8 CHEM3127
2. Below is a page from a laboratory course manual. Read the page carefully and then answer all
the questions on the following page. Note that you will not be carrying out this experiment in
the laboratory.
Experiment 2: Stereoselective conversion of D-glucose pentaacetate to n-Dodecyl-
2,3,4,6-tetraacetylthioglucopyranoside
Important: Ensure all your glassware is thoroughly dry before starting this experiment
(no water or acetone residues)!
Place D-glucose pentaacetate (2 g) in a dry flask containing a stirrer bar and fit with a Suba Seal and
a nitrogen balloon. Before adding the liquid reagents purge this flask with nitrogen for 15 minutes.
Next add dry dichloromethane (28 mL), then dodecanethiol (1.36 mL), followed by boron trifluoride
diethyl etherate, BF3.Et2O, (0.77 mL) dropwise from a syringe to the stirred solution. Stir at room
temperature for 1 hour, then run a TLC using a 8:2 hexane:ethyl acetate mobile phase. Visualise your
products on TLC plates using potassium permanganate or phosphomolybidic acid (PMA) dip. Dip your
full TLC plate in using tweezers. The TLC plate will stain purple (for permanganate) or yellow (for PMA
dip), but any compounds present such as alcohols will give yellow spots (permanganate) or blue spots
(PMA).
If the reaction is complete, remove the Suba Seal and immediately add triethylamine (1 mL) dropwise,
otherwise consult a demonstrator. Then reduce the solvent to a quarter of the initial volume, on the
rotary evaporator, but do not fully remove it, as you will need your product dissolved in minimal DCM
for the next step (flash column chromatography).
Isolate the product by column chromatography using the eluent system for your TLC. After removing the
solvent using a rotary evaporator, place your final product on the high vacuum line for 10-15 minutes to
remove any residual solvent.
Prepare your sample for submission.

Page 8 of 8 CHEM3127
(a) Complete a COSHH Chemical Risk Assessment for this experiment. A partially filled COSHH
Chemical Risk Assessment template MS Word document has been provided. Edit this
document and then save as a PDF for submission.
[30 marks]
(b) This experiment is the stereoselective conversion of D-glucose pentaacetate to n-dodecyl-
2,3,4,6-tetraacetylthioglucopyranoside.
(i) Explain why it important to exclude water from this reaction;
(ii) State, giving reasoning, what is the minimum size of flask should be used for this
reaction;
(iii) Explain the stereochemical outcome of this reaction. Include a mechanism in your
answer.
[10 marks]
(c) Thin Layer Chromatography is used to monitor the progress of this reaction.
(i) Explain why potassium permanganate or phosphomolybidic acid dip must be used.
(ii) Explain what can be deduced from the TLC plate shown below in Figure 4.
(iii) From the TLC place shown in Figure 4, calculate the Rf value for spot A and spot B.
(iv) Explain what difference you would expect to see in the TLC experiment if a 1:1
mixture of hexane:ethyl acetate was used instead of 8:2 hexane:ethyl acetate.
[10 marks]
Figure 4: TLC plate where (i) = glucose pentaacetate; (ii) = co-spot (reaction mixture + glucose
pentaacetate); (iii) = reaction mixture; (iv) = co-spot (reaction mixture + dodecanethiol);
(v) = dodecanethiol
END