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SCHOOL OF CHEMISTRY


SENIOR CHEMISTRY



CHEM3119 Materials Chemistry
Generic skills plus

PROJECT E: Ferrocene


EXPERIMENT E1: PREPARATION OF FERROCENE AND A DERIVATIVE
EXPERIMENT E2: SPECTROSCOPIC STUDIES OF FERROCENE AND ACETYLFERROCENE
EXPERIMENT E3: FURTHER INVESTIGATIONS OF FERROCENE
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CONTENTS

Page

E1:

Preparation of Ferrocene and a derivative

5

E2:

Spectroscopic Studies of Ferrocene and Acetylferrocene

11

E3:

Further Investigations of Ferrocene

- Electrochemisty of Ferrocen 17
- Your own Investigations 21




Appendices
23
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5
EXPERIMENT E1: PREPARATION OF FERROCENE
AND A DERIVATIVE

Introduction
Organometallic chemistry has developed into a major branch of inorganic chemistry. Defined as
the chemistry of the metal-carbon bond, its area of interest extends from various aspects of valence
theory to chemical technology, from bonding in metal π-complexes, for example, to the catalytic
synthesis of industrial alcohols and aldehydes.
Organometallic chemistry owes much of its present status to the discovery of ferrocene (Ref. 1) in
1951 and to work done subsequently on the chemistry of cyclopentadienyl compounds (Ref.2).
Since the preparation of ferrocene involves a number of techniques typical of organometallic
chemistry it is practically and historically an appropriate synthesis for senior chemistry students to
undertake.

Experimental Method
Before commencing this experiment, you must complete a HIRAC form and submit it to a
Demonstrator, along with your Name/SID, to be assessed. Your HIRAC marks will be
entered into the system. You may get your HIRAC assessed on any day prior to the
session/experiment that you are about to start.

CAUTION: Cyclopentadiene exists in equilibrium with its dimer. The equilibrium strongly
favours the dimer at and above room temperature. Cyclopentadiene is therefore stored in the
freezer in the service room.

Both ferrocene and acetylferrocene, however, are air and water-stable solids at room temperature.

i. Synthesis of Ferrocene, (η5-C5H5)2Fe, di-η5-cyclopentadienyliron.
Obtain the kit for this preparation from the appropriate bench (lab 439, check WHEREIS list). Make
sure that the apparatus is clean and dry. The Ferrocene workstations have been set up for you in the
fume hoods near the instrument rooms, lab 439. Workstations consist of hotplate stirrer (although
heating is not required), nitrogen line with an adaptor and the bubbler line. Please make sure that
the workstations remain intact after use; reassemble all apparatus and wipe any spills from the
hotplate stirrer and the adaptors. Clean the glassware and return your kit to its designated location.
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Figure 1. Experimental Setup for Ferrocene Synthesis



Add 25 g of powder potassium hydroxide using a powder funnel. Set up the apparatus shown above
in Figure 1. Place the magnetic stirrer bar in the flask, attach dropping funnel, nitrogen and bubbler
lines. Flush the system with nitrogen for a few minutes before adding the reagents. Add 60 mL of
1,2-dimethoxyethane to the flask through the middle neck and commence stirring. Reattach the
dropping funnel and flush the system with nitrogen for another 10 min. The flow of nitrogen should
be adjusted so that a steady flow passes through to the bubbler.

CAUTION: See a demonstrator before you use the nitrogen.


Obtain iron(II) chloride tetrahydrate (FeCl2·4H2O) from the desiccator. Iron(II) chloride should be
green-yellow in colour, if it is more like orange it has oxidised into iron(III) chloride and should
not be used. Make sure that exposure of Iron(II) chloride to the air is reduced to a minimum. Use
6.5 g of Iron(II) chloride. Crush any lumps and very quickly dissolve in 25 mL of dimethylsulfoxide
(DMSO). Ensure that dropping funnel’s tap is closed. Transfer the solution of Iron(II) chloride
in DMSO to the dropping funnel and stopper the funnel. Do not add the solution to the flask at this
stage.
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Obtain 6 mL of freshly distilled cyclopentadiene from the service room. Keep this on ice during
collection and addition. Remove the nitrogen line going to the bubbler and (with the nitrogen still
flowing) add 5.5 mL of cyclopentadiene dropwise from a Pasteur pipette. Replace the adaptor to
the nitrogen bubbler and stir the mixture vigorously. The empty cyclopentadiene vial should be
capped and placed in the broken glass bin.
Do not wait for too long before adding the next reagent. The solution will warm up and
the cyclopentadiene will polymerise.


Slowly, over 15 min, add the iron(II) chloride solution to the stirred mixture in the flask. Stir the
mixture for a further 20 min.
Turn the nitrogen off and pour the reaction mixture into a mixture of 90 mL of 6 M hydrochloric
acid and 100 g of ice (in 500ml beaker). Rinse the reaction flask with some of the acid/ice slurry.
Stir for 15 min over an ice-bath and collect the precipitate on a filter paper using a Buchner filter
and by filtering at the pump. Wash the precipitate with four 25 mL portions of water. Transfer up
the crude product it to a 250 mL beaker and extract it with boiling petroleum spirit (petroleum
benzine 40-60) as follows: add 50 mL of the solvent to the beaker containing the crude ferrocene
and bring to the boil on a steam bath. Decant the hot solution into a 500 mL conical flask containing
15 g (or more if required) of anhydrous sodium sulfate. Repeat with further 50 mL portions of the
solvent. Continue collecting the portions of dissolved ferrocene in hexane (orange/yellow in colour)
into a conical flask until the decanted solvent becomes colourless. This means you have extracted
all ferrocene and might be left with some insoluble impurities in the flask.

Combine the extracts and vigorously shake for 5 min with sodium sulfate. Carefully decant the
solvent from the conical flask or filter through cotton wool to remove the sodium sulfate. Place the
filtrate in a weighed evaporating basin (crystallization dish) and allow to evaporate to dryness at
the back of the fume hood. DO NOT HEAT SOLUTION (to speed up the process) – your
ferrocene will sublime along with hexane. Solution can be left in the evaporating basin until your
next session. Record your yield. Reserve 0.3 g for further purification by sublimation and use some
of the remainder for the preparation of the acetyl derivative.

ii. Purification by Sublimation.
Collect a pyrex petri dish and a cover from the appropriate bench. Spread a sample (~ 0.3 g) of the
crude ferrocene on the bottom of the petri dish. Put the cover on the dish. Half fill a 500 mL beaker
with crushed ice. Place the petri dish containing the ferrocene on the hot-plate, preheated to 50 °C,
in the fume hood and immediately place the beaker of ice on top of the petri dish. Increase the
temperature to 100 °C. DO NOT PLACE AN EMPTY PETRI DISH ON THE HOTPLATE –
IT WILL CRACK. The ferrocene will start to sublime and deposit on the glass cover dish
immediately below the ice in the cold zone. When the ferrocene has all transferred to the top (which
means not much solid left on the bottom part of the petri dish), slide off the beaker of ice and using
a pair of tongs carefully remove the petri dish off the hotplate. When it has cooled to a room
temperature carefully remove the top cover and collect the sublimed ferrocene. Record your yield
and submit the sample. (consider 0.3g is your 100%, calculate % yield from the mass you have
collected)
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iii. Synthesis of acetylferrocene, (η5-C5H5)(η5-C5H4COCH3)Fe

To a mixture of 1.5 g of ferrocene and 5 mL of acetic anhydride in a small dry 50 mL round bottom
flask, add dropwise with constant stirring, 1 mL of 15 M (syrupy) phosphoric acid. Stopper the
flask with a calcium chloride drying tube. Heat the mixture on a hotplate at 50°C while stirring
vigorously for 25 min, then pour onto 20 g of ice in a tall 250 mL beaker. Avoid washing out too
much of the intractable tar from the 50mL round bottom flask. When the ice has melted, neutralize
the mixture by slowly adding 50% sodium hydroxide solution, dropwise.

CAUTION: Adding sodium hydroxide too quickly can overshoot the pH change.

Cool the mixture in an ice bath and filter off the solid using a vacuum filtration. Wash with 250 mL
of water. The solid contains a mixture of ferrocene, acetylferrocene, diacetylferrocene and an
intractable tar. These will be separated using column chromatography.
To select an appropriate solvent for column chromatography, trial different solvent systems using
TLC. The aim is to find a solvent system in which your compound is well separated from others,
and moves at least one third of the way up the TLC plate. First test the separation using 100%
hexane as the solvent, to give you a reference point for your other trial solvents. Think about how
including some ethyl acetate in your solvent system will change the polarity relative to 100%
hexane. And how will this change in solvent polarity effect how your compounds move up the TLC
plate?
Conduct a minimum of four TLC trials, using the following solvents. You may wish to improve
the separation by trialing other mixtures or adjusting the solvent ratios.
(a) hexane
(b) ethyl acetate
(c) hexane:ethyl acetate 9:1
More information about how to perform TLC analysis is given in the Appendix to this lab manual.
Take photographs or make schematic diagrams of your TLC plates to submit with your sample.


On the basis of these tests select a suitable solvent or combination of solvents to purify a sample of
the impure acetylferrocene by column chromatography. Note that it is common to use one solvent
system to elute one analyte, and then increase the polarity of the solvent system to elute another
analyte. Check with a demonstrator that you have made an appropriate choice. Take a photograph
of your TLC plates or make schematic drawings for inclusion in your electronic notebook.

iv. Purification by Column Chromatography
Read the general instructions for column chromatography in the Appendix to this lab manual.
Weigh 1.0 g of impure acetylferrocene into a 50 mL conical flask, and dissolve in minimum amount
of hot hexane while heating on a steam bath. If sample doesn’t dissolve completely add a few drops
of ethyl acetate. You will need to add the solution to the column hot.
Prepare a bed of silica in hexane in a B29 chromatography column with a cotton wool plug. To dothis,
pour a small volume (about 10 mL) of hexane into the column and run out the air bubbles in the cotton
wool and stopcock region. Pour a slurry of silica in hexane through a small funnel placed in the top of
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the burette. Rinse the silica into the column with hexane from a Pasteur pipette and, at the same time,
run hexane from the bottom of the column at a steady rate. Never allow the solvent level to fall
below the top of the adsorbent.
When the bed depth is about 15 cm, run the solvent down to the top of the silica and load the impure
acetylferrocene solution dropwise onto the top of the column until the remainder can be poured in
without disturbing the surface of the adsorbent. Avoid adding any tar that may have accumulated
in your crude product mixture.
With a small amount of pressure (N2) push the solution down the column until its surface is level
with the top of the silica. Carefully add 0.5 mL of the eluent from a Pasteur pipette and again run
the liquid down to the bed level. Repeat this procedure until all eluent has been added and then
proceed with the elution using the solvent(s) or solvent mixture you have selected. Further, the
elution once started should be completed as soon as possible, as blue oxidation products are formed
on standing.
Elute the components through the column and collect fractions (in a rack of test tubes) until the
ferrocene begins to be eluted. You should see a slow moving reddish-orange band staying on top
while a fast moving yellow band is collected into the first test tube. The yellow band is ferrocene
and the reddish-orange band is acetylferrocene.
Collect ferrocene and acetylferrocene fractions in pre-weighed 250 mL beakers and reduce the
volume to approximately 10 mL on a steam bath. You must monitor this reduction of volume
carefully – DO NOT allow the products to dry completely or they will sublime off the beakers and
you will have no product.
Allow the remaining solvent to evaporate in a fume hood at room temperature. Weigh the crystals
from each fraction and record the yields. To confirm the purity of the acetylferrocene and ferrocene
after the column, run a single TLC plate for both samples, using the same solvent as was used to
elute the acetylferrocene. Take a photograph of your TLC plate or make a schematic drawing for
inclusion in your electronic notebook.

v. Infrared Spectra
Record the infrared spectra of ferrocene and acetylferrocene using the ATR-IR (see spectroscopy
manual) for the range 4000 to 400 cm-1. Assign as many peaks as possible. Save your infrared
spectrum as an ASCII file (.csv) and replot using Excel or other graphing software.
vi. Melting points
Determine the melting points of the sublimed ferrocene and chromatographed products and
compare these with the literature values.



Submit the following samples to the Service Room (see “E” assessment document on Canvas):
- crude ferrocene (marked on appearance and yield calculations)
- sublimed ferrocene (marked on appearance and yield calculations)
- crude acetylferrocene (not marked on appearance or yield), can still submit if you like.
- column purified acetylferrocene (marked on appearance and yield calculations)
- column purified ferrocene (marked on appearance and yield calculations)
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11
EXPERIMENT E2: SPECTROSCOPIC STUDIES OF
FERROCENE AND ACETYLFERROCENE

Experimental Method
Before commencing this experiment, you must complete a HIRAC form and submit it to a
Demonstrator, along with your Name/SID, to be assessed. Your HIRAC marks will be entered
into the system. You may get your HIRAC assessed on any day prior to thesession/experiment
that you are about to start.
Please notify the Service room staff the day before you wish to carry out metal
decomposition. A large hot plate will be set up in the first, designated fume hood for Wet
Ashing.

i. Determination of metal content (wet ashing and spectroscopic analysis)
Wet Ashing is an important preliminary step in many metal determinations. It is used to decompose
organic and other matter and to bring metals into solution in a form which is suitable for analysis
and in a comparable matrix to the standards.
Analyze sublimed ferrocene and acetylferrocene for iron using ICP-OES or AAS spectroscopic
techniques and compare the results with expected (stoichiometric) iron content. Prior to starting
Wet Ashing, consult a demonstrator regarding your calculations for the required amounts of samples
and final concentrations of just Fe metal Ions after the dilution. AAS/ICP standards are provided
for you by the Service Room (2-10ppm). The solutions have been prepared in 0.1 M HCl to
improve stability.

Metal Cr Mn Fe Co Ni Cu

Concentration range 2-6 1-6 2-10 2-10 2-10 1-8
(mg metal L-1)



Proceed with metal decomposition by wet ashing before diluting your samples for analysis.

Read through the method. Calculate the weight of sample required and the subsequent volume
of the first dilution (for the final dilution to end up within the concentration range of the
standards 2-10ppm). Check your calculations with a demonstrator prior to making solutions to
avoid overdiluting your samples passed the lower range. It is good practice to analyze a
compound as soon as possible after synthesis followed by decomposition and to perform the
analysis in duplicate.
Accurately weigh duplicate samples of each Ferrocene and Acetylferrocene (0.05-0.1g) for
analysis. Record the mass. Add samples to 50 - 100 mL conical flasks.
When wet ashing the samples, take extreme care and add the acids very slowly. In the designated
fume hood, place a small stemless funnel on top of each conical flask (do not put them on the
hot plate at this stage). Add approximately 2 mL of 18 M sulfuric acid to your sample. Then
add approximately 2 mL of 15 M nitric acid and swirl gently to mix.
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Transfer conical flasks onto hot plate and heat, set the temperature to 250 0C. Take care as
oxides of nitrogen will vigorously evolve. Continue heating until all the water has been evolved.
This is indicated by the distillation of oily sulfuric acid up the walls of the conical flask and the
appearance of white SO3 vapor.


NOTE: This stage might take 24 h or longer. Add all acids before leaving the conical flasks on
the hot plate. Service room staff will monitor and continue with digestion until your next session.
If the solution is still dark (black or brown) or if dark particles persist after the initial treatment
with 15 M nitric acid /18 M sulfuric acid, cool to room temperature andadd more 15 M nitric acid
(~5 mL) and heat again on the hot plate. Repeat this procedureuntil all organic matter is oxidised
and the solution is clear. Some anhydrous metal saltsmay appear on the bottom of the flask (as
white/greenish precipitate). These will be dissolved later by adding deionized water while making
up your solution.


Allow the conical flask and contents to cool, then carefully dilute the concentrated acid
solutions with approximately 20 mL of deionised water. If the white anhydrous metal salts do
not immediately dissolve (this is usually the case with nickel and iron salts), it should happen
at later stages of dilution (no visible solid present).
From this point you will need to calculate and work out whether to dilute your samples in 500
or 1000ml of the deionized water. Then, pipette 10.0 and 20.0mL aliquots of each of the
resulting solution into 100 mL volumetric flasks and adjust to volume with 0.1 M HCI. Label
all solutions.
Your final concentrations should be within the range of the standards from 2-10mg/L.

Metal Determination

Two common methods of metal analysis are available for use in the second and third year
teaching labs: Microwave Plasma Atomic Emission Spectrometers (MP-AES) and ICP-OES.
Check with the Service Room about availability of the instruments.

When reporting the results, quote the percentage metal found in your sample, and the value
calculated for a pure compound.
ii. NMR Spectra
Collect 1H NMR spectra of your two compounds (dissolve approximately 20 mg in 0.5-1 mL
CDCl3). Identify the hydrogen atoms that give rise to the peaks.

iii. Mass Spectra
You will be provided with spectra. Also provided is a bar graph showing the abundance of the
important peaks relative to the most intense one (taken as 100%). Make a table of these peaks and
the relative abundance of each. Where possible, identify the species represented by each peak.
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References
Properties, Bonding and Chemistry:
1. G. Wilkinson and F. A. Cotton, in Progress in Inorganic Chemistry, Vol.1, F.A. Cotton
(ed.), Interscience, New York, 1959, pp 1-124 (a more advanced reference).
2. J. E. Huheey, Inorganic Chemistry, Harper and Row, New York 2nd edn, 1975, pp 465-
478.

Mass Spectra:
3. J. Charalambous in Mass Spectroscopy of Metal Compounds, J. Charalambous (ed.
Butterworth, London, 1975, pp 19-27.
1. V. M. Parikh, Absorption Spectroscopy of Organic Molecules, Addison-Wesley Publishing
Company, Reading, 1974, pp 152-153.

Infrared Spectra:
2. K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds,
Wiley-Interscience. New York, 3rd edn., 1978, pp 388-393.
3. E. Maslowsky, Vibrational Spectra of Organometallic Compounds, Wiley-Interscience,
New York, 1977, pp 308-321, 365-367.

Electronic copies of these references are available on Canvas.
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Sample: Ferrocene Acetylferrocene
Solvent: CCl4 CS2
Concentration: Saturated Saturated
Cell path: 0.1 nm 0.1 nm
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16
EXPERIMENT E3: ELECTROCHEMISTRY OF
FERROCENE AND ITS DERIVATIVE

Introduction
Ferrocene
Ferrocene is well known to undergo reversible, one-electron oxidation to its ferrocenium ion:



This oxidation process occurs at a potential of E° (Fc+/Fc0) = 0.40 V vs. SHE (standard hydrogen
electrode). This, along with its good solubility in common organic solvents, has led to the
widespread use of ferrocene as an internal standard in electrochemical analyses, particularly in non-
aqueous electrolytes.1 Different structural factors such as change in the metal ion and substitution
of the cyclopentadienyl ring alters the formal oxidation potential (E1/2) of the one-electron oxidation
process.

Cyclic Voltammetry (CV)
A common electrochemical technique known as cyclic voltammetry will be used to investigate the
change in E1/2 of ferrocene caused by acetylation of the cyclopentadienyl ring. Cyclic voltammetry
sweeps the potential of the working electrode linearly and measures the resulting current.2 As
suggested in the name, the sweep direction is reversed at a switching potential and provides
information on the reversibility of the observed redox processes. As the applied potential
approaches that of a redox process, the faradaic current increases (reduction process) or decreases
(oxidation process) giving rise to a peak in the cyclic voltammogram (Figure 1). The non-zero
current observed in a cyclic voltammogram in the absence of any redox processes is called the non-
faradaic or capacitive current and is due to a build-up of charge at the working electrode.
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Figure 1. An example of a typical cyclic voltammogram involving one reversible redox process. Peak currents
ipa and ipc, and peak potentials Epa and Epc are annotated. Figure reproduced from Reference 3.


The formal redox potential (E1/2) can be determined by:
, + ,
1/2 = 2
where Ep,a is the potential of the anodic peak (in Volts) and Ep,c is the potential of the cathodic peak
(in Volts).

Scan rate dependence
The Randles-Sevcik equation describes the relationship between scan rate and peak current:
1
2

= 0.4463 ( )

where ip is the peak current (Amp), n is the number of electrons transferred (for ferrocene n = 1), F
is the Faraday constant (C mol-1), A is the surface area of the working electrode (cm2), C is
concentration (mol cm-3), D is the diffusion coefficient (cm2 s-1), v is scan rate (V s-1), R is the gas
constant (J K-1 mol-1), T is temperature (K). The diameter of working electrode is 3mm.
In cyclic voltammetry, the current which passes through the working electrode is limited by
diffusion of the analyte to and from the electrode surface. Thus, the concentration of analyte at the
electrode surface changes with scan rate, i.e., larger peak currents are observed at faster scan rates.
In the case of a reversible redox process, the peak current is governed solely by diffusion. By
plotting ip vs. v1/2, the diffusion coefficient (D) can be determined from the slope.

Experimental Method
Before commencing this experiment, you must complete a HIRAC form and submit it to a
Demonstrator, along with your Name/SID, to be assessed. Your HIRAC marks will be
entered into the system. You may get your HIRAC assessed on any day prior to the
session/experiment that you are about to start.
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i. Setting up the electrochemical apparatus

Prepare a 0.1 M stock solution of tetrabutylammonium bromide (supporting electrolyte; 25 mL) in
dry acetonitrile. Dry acetonitrile can be obtained from the Puresolv solvent purification system –
please ask a demonstrator to assist you with this. Use this electrolyte to make up 10 mM solutions
of ferrocene (10 mL) and acetylferrocene (10 mL), separately. Note: use sublimed ferrocene and
column-purified acetylferrocene. Keep the rest of the supporting electrolyte to run a background
for your voltammetry experiment.
Ask your demonstrator to gently polish a glassy carbon working electrode (measure its diameter
for area calculation) and Ag/AgCl reference electrode using 0.05 μm alumina on a microfibre cloth.
Rinse these electrodes with deionised water and acetone, and allow to dry. Rinse the Pt-coated
counter electrode and electrochemical cell with acetone and dry under a flow of nitrogen.


Figure 2: electrodes and cell


Pipette approx. 2 mL of electrolyte solution into the glass cell and screw on the Teflon lid. Place all
three electrodes: the glassy carbon working electrode, Pt-coated counter electrode and Ag/AgCl
reference electrode, into the glass cell through the designated holes in the Teflon lid. Ensure that
approx. 1 cm of the electrodes are immersed in the electrolyte and you attach the clips as shown in
Figure 3 (the connection is very sensitive). Clip the electrodes to the potentiostat using the alligator
clips in the following order: GREEN to the glassy carbon working electrode, RED to the Pt/Ti
counter electrode and YELLOW to the Ag/AgCl reference electrode. Make sure the alligator clips
of each electrode are not touching any neighbouring electrodes or clips and that the three electrodes
are not touching – this is to avoid short-circuiting the system! If you get results that appear to be no
signal or noise it is likely that the electrodes are not connected correctly. Readjust and rescan.
Use a N2 line equipped with a drying tube followed by an acetonitrile bubbler, syringe and needle
to degas the electrolyte (approx. 5 min). Connect the N2 line and acetonitrile bubbler to a retort
stand for stability. Once degassed, raise the needle out of the solution but keep it within the cell to
maintain a headspace of N2.
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Figure 3. Attachment of electrodes for cyclic voltammetry.


ii. Cyclic voltammetry
Run a cyclic voltammogram (CV) of the electrolyte itself (background measurement). This should
show no peaks, indicating there are no electrochemically-active species present. Discard the
electrolyte into the appropriate waste container and wash the cell with acetone and dry under a flow
of N2.
Introduce approx. 2 mL of the ferrocene solution into the cell and degas under N2 for 5 min. Raise
the needle out of solution and run a CV under the same parameters as for the background. Collect
CVs at the following scan rates: 10, 20, 50, 100, 200, 400 and 800 mV/s. Run cyclic voltammetry
on the acetylferrocene solution in the same way.
References

1. Astruc, D. Eur. J. Inorg. Chem. 2017, 2017, 6-29.
2. Wang, J., Fundamental Concepts. In Analytical Electrochemistry, John Wiley & Sons,
Inc.: 2006; pp 1-28.
3. Electrochemistry,
http://okbu.net/chemistry/mrjordan/inorganic1/electrochem/ECHEM1.HTML, accessed 28
Jul 2017.
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PART 2: YOUR OWN INVESTIGATIONS
Before commencing this experiment, you must complete a HIRAC form and submit it to an
Academic, along with your Name/SID, to be assessed. Your HIRAC marks will be entered
into the system. You may get your HIRAC assessed on any day prior to the
session/experiment that you are about to start.
In your remaining lab sessions, together with your lab partner, design and implement further
investigations into reaction kinetics, the reactions studied in experiments D1–D3, or similar related
systems. Before beginning your investigative experiment, you should follow the investigative
experiment checklist on Canvas. This involves checking with a demonstrator and the service room
that your proposed experiment is feasible in the laboratory and that appropriate equipment and
chemicals are available. You should then check with the academic supervisor (or whoever they
suggest) that your experiment is sensible and can be performed within an appropriate time-frame.
You must then prepare a HIRAC for approval before beginning any new experimental work. The
HIRAC must be signed off on by the academic in charge of the laboratory and must be submitted
together with your report. Your additional investigations must relate in some way to at least one of
experiments completed as part of this project. A number of suggestions are given below but you are
not limited to these.

Examples of investigative experiments you might consider are:
• How does varying the reaction conditions for the synthesis of acetylferrocene (e.g.
temperature, solvent) affect the product and yield?
• What other characterisation measurements of ferrocene and acetylferrocene could be
undertaken?
• Can 1,1'-diacetylferrocene be prepared and what is the effect of a second acetyl group on
the cyclic voltammetry of the compound?
• Investigate the cyclic voltammetry of other ferrocene derivatives and compare the effect of
substitution on redox potentials.
• What is the effect of different solvents on the redox potentials of the compounds?
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APPENDIX
APPENDIX A: GENERAL METHOD FOR TLC
To get a good separation between your products and to use as little solvent as possible, the key is
to test potential solvent systems before setting up your column. To do this, you will need to run thin
layer chromatography (TLC) using aluminium sheets coated with silica.
TLC is a method that allows you to see what is happening in your reaction – how many products
are forming and whether your reagents are used up. It does this by separating compounds based on
their polarity. Compounds are loaded to the bottom of the stationary phase (the silica), and solvent
is run up the plate. More polar compounds interact more with the silica, so take longer to move up
the plate. You can change the polarity of your solvent system (for example from hexane to
dichloromethane) to make everything move faster.
In order to run a TLC:
1. Obtain a silica TLC plate (aluminium-backed) and a capillary tube (glass or plastic), plus
a 50 mL beaker to act as your “developing tank”.
2. Mark a baseline on the TLC plate with a soft pencil and mark off and label the points you
will spot. (e.g. starting materials, reaction mixture)
3. Repeatedly spot a small volume of your dissolved compounds/reaction mixture with the
capillary, making sure not to put too much on that the spot to let it spreads into the others.
The resulting spot should be 1–2 mm in diameter.
NOTE: It doesn’t matter what solvent your compounds are dissolved in, as long as it has
evaporated by the time you run the TLC plate.
4. Pour some solvent into the bottom of your beaker so that the level is below the baseline of
your TLC plate.
5. Carefully stand the TLC plate in the beaker and place a watch glass on the top, as shown
in Figure


Figure 1: TLC set-up.

6. Once the solvent is ~ 1 cm from the top, remove the plate, mark the position of the solvent
front (how far the solvent’s got to) with a pencil, and allow it to dry.
7. Depending on your compounds, you can visualise them under the UV light, or with a TLC
stain. Your TLC should look something like the one in Figure 2.
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Figure 2: Schematic of a TLC plate.

8. TROUBLESHOOTING:

a. If your TLC shows a big long streak up the plate, you spotted on too much compound
at the bottom. Try diluting your sample and/or spotting less times and run it again.
b. If your spots have remained at the bottom of the plate, try increasing the polarity of
your solvent to obtain and Rf of 0.3. (Rf = distance compound travelled/distance
solvent travelled).
c. If your spots have moved very quickly and are all at the top, try reducing the polarity
of your solvent, as this will give you better separation between compounds and
potentially reveal some new spots that have run very quickly together. The ideal Rf
is around 0.3. (Rf = distance compound travelled/distance solvent travelled).


You can also watch demonstration that have been posted to YouTube on how to run your
TLC plates: https://www.youtube.com/watch?v=Ah9lPqHz7FY
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APPENDIX B: GENERAL METHOD FOR COLUMN
CHROMATOGRAPHY
Column chromatography is a technique that allows you to separate compounds by their polarity in
order to purify them. It is like a large-scale version of a TLC (see appendix A). Compounds are
loaded to the top of the stationary phase (the silica), and solvent is run through the column. More
polar compounds interact more with the silica, so take longer to move through the column. You can
change the polarity of your solvent system (for example from hexane to dichloromethane) to make
everything move faster. You can choose an appropriate solvent system for your column by running
some test TLCs to see what separates your compounds well.
The set-up for a column is shown in Figure 1.





Your
sample
is loaded
into the
silica
with
sand
on top

Eluting Solvent
Sand
Silica
Sand
Cotton Wool

Test tubes for
fractions


Figure 1: Chromatography column: prior to elution (left), during elution (right),
note solvent above the sand in the column.
In order to run a column:
1. Place a small wad of cotton wool in the bottom, pushing down with a metal rod from
the front bench.
2. In order to estimate how much silica you will need, fill the column to a height of about
15cm, and then pour it back out into a conical flask.
3. Pour in a thin layer of sand until the bottom of the column is level.
4. Make a slurry of your measured silica and your chosen solvent system and pour it into
the column. You can push the solvent through faster with a nitrogen adapter from the
Service Room. Let silica beads to settle to your 15cm measured.
5. When your silica is packed, add roughly 5 mm of sand on top of the silica.
6. Run the solvent down just to the top line of the sand and close the column tap at the
bottom. Carefully load your dissolved compound in with a minimum amount of
24
solvent on top of the sand. Run the solvent down until it reaches the top line of the sand,
then add 1-2 pipettes of solvent and run the solvent down to the top line of the sand. By
doing this, you are bringing your compound to reach the silica layer.
7. Fill the solvent to the top of the column, run solvent through the column and collect
fractions in test tubes at the bottom. Use TLC to check your fractions for the desired
compound.
8. Combine all fractions with the pure desired compound and remove solvent on the rotary
evaporator.
9. Dry your silica with the nitrogen line and discard into the silica waste.


You can also watch demonstration that have been posted to YouTube on how to set up and
run your chromatography columns:

Setting up a chromatography column: https://www.youtube.com/watch?v=pxXyMGV6SRY

Running a chromatography column: https://www.youtube.com/watch?v=dRVbGr_QbjI
25

APPENDIX C: GENERAL METHOD FOR RECRYSTALLISATION
Recrystallisation is a method that allows you to purify your desired compound from other impurities
based on their solubility. It requires using a solvent that your compound dissolves in at high
temperatures but will then crystallise out at low temperatures. By dissolving both impurities and a
compound in an appropriate solvent, either the desired compound or impurities can be removed
from the solution, leaving the other behind. Ideally, the impurities in your mixture will remain
soluble at low temperatures so when you filter your crystals, the impurities stay dissolved in the
solvent.
To do a recrystallization:
1. Heat a small volume of solvent on a steam bath or a hot plate
2. Slowly add hot solvent to your compound in a conical flask until it all dissolves. Try to
use a minimum amount of solvent and keep it hot to maximise the solubility of your
compound. The volume of added solvent will vary depending on the mass and solubility
of the product being recrystalized. While keeping the volume to minimum, make sure
that solvent is not evaporated to dryness, otherwise your soluble impurities will remain
in your recrystallized product.
3. When all your compound is dissolved, carefully move your flask to the side and allow
it to cool slowly. The slower you do your recrystallization, the larger your crystals will
be.
4. Collect and dry your product (crystals) by vacuum filtration.





5. TROUBLESHOOTING:
a. If there are impurities that do not dissolve at high temperature, you may need to
do a hot filtration. This requires warming some filtration equipment with some
hot solvent, and filtering off the insoluble impurities, then doing a
recrystallization as normal to remove the soluble impurities.
b. If your compound is not crashing out upon cooling, you may have used too
much solvent. Excess solvent can be easily removed by placing your dissolved
product back onto the hot late and evaporating some of the solvent to reduce the
volume. You can try to blow off some solvent with gentle stream of nitrogen while
heating it.
26
You can try to put your flask on ice to encourage recrystallisation and formation
of the crystals. If that doesn’t work, you may need to remove all the solvent and
start again.
27
APPENDIX D: RUNNING, PROCESSING AND INTERPRETING NMR
SPECTRSCOPY
NMR is a technique that allows us to ensure we have made the correct compound. It is a
spectroscopic technique that gives us information about the environment of atomic nuclei, normally
1H and 13C. It works by placing your compound in a magnetic field, and observing the nuclei
relaxation, which will change depending on the extent of the electron shielding, and the presence
of other surrounding nuclei. We can use the information from these relaxations to assign the
structure of our compound.
In order to run an NMR sample:
1. Dissolve approximately 10 mg of your compound in 0.5 mL of deuterated solvent from
the front bench – chloroform or DMSO. Make sure it is entirely soluble (you can test
solubility with the non-deuterated solvent).
2. Pipette the solution into an NMR tube.
3. Run an NMR experiment, following the instructions at the benchtop NMR.


There are a few aspects of our 1H NMR spectrum that we can use to obtain information about our
compound.
1. The chemical shift of the signals.
The chemical shift (along the x axis) of our signals tells us what environment the proton
signals are in. Generally, aliphatic protons show up near 1 ppm, and aromatic protons are
near 7 ppm. This has to do with the extent of electronic shielding. Below is a table
summarising the shifts of protons in typical chemical environments.

Table 1. Typical 1H chemical shifts (ppm relative to TMS) for protons
in different chemical environments

Hydrogen, H,
environment
Chemical Shift Hydrogen, H,
environment
Chemical Shift
RCH3 0.9-1.0 ROH 1-5

RCH2R

1.2-1.7



3.7-6.5
R3CH 1.5-2.0 Aromatic hydrogen: ArH 6.0-8.7



2.0-2.3



9.5-10.0



1.5-1.8



10-13
28
2. The area under the signals (the integral).
The integrated area under the signals is proportional to the number of protons in that
environment. So for example, if you have 1 aldehyde proton and 3 aliphatic protons, the
relative integrals will be 1:3.

3. The splitting of the signals.
The presence of nearby nuclei will split the signal of individual environments into more
than one peak. The splitting rule is that the number of peaks = the number of adjacent
protons, plus 1.
For example, a doublet tells us a proton is next to one other proton, and a triplet indicates
it is next to two other protons.
Consider the 1H NMR spectrum for 1,1,2-trichloroethane shown in Figure 1, where the
individual signals are enlarged to show the splitting patterns.


Figure 1: 1H NMR spectrum of 1,1,2-trichloroethane.

The signal for the equivalent Ha protons are seen as a doublet, because they are next to
one other proton (Hb), and the signal for the Hb proton is seen as a triplet, because it is
next to two other protons (Ha).

Note: the resolution of the SpinSolve 1H NMR in the 3rd year laboratory is such that it is not
always possible to resolve splitting.

In order to process an NMR spectrum you have obtained:

1. Open the topspin program on one of the computers in the third year laboratory.
2. Drag in the fid file of your compound.
3. You can zoom in by clicking and dragging across the region of interest, and zoom out
using the minus magnifying glass button.
4. Under the “process” tab, you can select “pick peaks”. Select the roller to start picking.
Drag a box across the peaks you want topspin to assign. This way you know the
29
exact chemical shifts of your signals. When you are done click on the save and return
icon.
5. Under the “process” tab you can select “integrate”. Select the roller to start integrating.
Drag across the peak you would like topspin to integrate. You can calibrate your
integrals by right clicking on an integral and selecting “calibrate current integral”. When
you are done click on the save and return icon.
6. To plot the spectra for printing, click “Start” and then “plot”.


If you would like to display and compare multiple spectra on the one screen:

1. Drag both of the files you would like to overlay into topspin, one after the other. You
will be able to see them in the “last 50” tab on the left”.
2. Press the overlay button in the program top bar.
3. Drag across the second spectrum from the left.
4. If they are on top of one another, press the offset button in the spectrum top bar.
5. If you would like to print or save, first export the active window as a pdf (under file,
export).



13C NMR spectra

13C NMR spectra are less intense than 1H spectra. The magnetic moment of a 13C nucleus is smaller
and the natural abundance of 13C is only about 1%. This means a lot of signal averaging is required
to reduce the signal-to-noise in a 13C NMR spectrum. The inherent intensity for some types of 13C
nuclei is also very small. Together, this means that, in general, we cannot use peak integration to
tell us how many of a given type of 13C nuclei there are in a molecule.

The low natural abundance of 13C means we do not see spin-spin coupling between neighbouring
13C nuclei. There is, however, heteronuclear coupling between 13C carbons and the protons to
which they are bound, where carbon-proton spin-spin coupling constants are very large, of the
order of 100 – 250 Hz.
With the development of more modern spectroscopic methods it has become possible to use a
programmed sequences of radio frequency pulses to determine other structural features from 13C
NMR. One of these techniques is distortionless enhancement of polarisation transfer (DEPT), which
can be used to give the number of attached H. In a DEPT spectrum, C with an odd number of
attached H have a positive phase (up) and those with an even number of H have a negative phase
(down). Thus -CH3 and CH peaks appear as normal and -CH2- peaks appear inverted (quaternary
C are not usually seen). This allows the number of H attached to C to (usually) be deduced.
30
Table 1. Typical 1H and 13C chemical shifts (ppm relative to TMS) for protons and carbon nuclei
in different chemical environments
Hydrogen, H,
environment
Chemical Shift Carbon, C,
environment
Chemical Shift
RCH3 0.9-1.0 RCH3 13-16
RCH2R 1.2-1.7 RCH2R 16-25
R3CH 1.5-2.0 R3CH 25-35



2.0-2.3



18-22



1.5-1.8



28-32
RNH2 1-3 RCH2NR2 35-45
ArCH3 2.2-2.4 RCH2OH 50-65

2.3-3.0

65-70
ROCH3 3.7-3.9 ROCH2R 50-75




3.7-3.9




50-75

ROH

1-5



115-120



3.7-6.5



125-140
Aromatic hydrogen: ArH 6.0-8.7 Aromatic carbon 125-150




5-9


Carboxylic acid
derivatives


165-185



9.5-10.0



190-200



10-13



200-220
31
Structure Determination:

Given an unknown molecule’s empirical formula, for example from mass spectrometry, 1H and 13C
NMR spectra (sometimes in combination with UV-vis absorbance and IR spectra) can be used to
identify its structure.
As an example, consider a molecule with an empirical formula C15H14O. Infra red spectroscopy
gives a strong absorption at approximately 1700 cm-1, characteristic of a carbonyl group.
Schematics of its 1H NMR spectrum and 13C NMR spectrum are shown in Figures 3 and 4,
respectively.



Figure 3: 1H NMR spectrum, relative to TMS, of unknown molecule, empirical formula C15H14O.
Relative integrated peak areas as indicated.



Figure 4: 13C NMR spectrum, relative to TMS, of unknown molecule, empirical formula C15H14O.

From Figure 3, the 1H NMR spectrum, there are 10 protons with chemical shifts indicative of
aromatic H atoms. This suggests the molecule has two phenyl groups, C6H5. The 13C NMR
spectrum, Figure 4, has 7 peaks, with four indicating aromatic carbon atoms. The fact that there are
only four peaks in the aromatic region suggests that the two phenyl groups are equivalent. There
are now only three more carbon nuclei in the molecule to account for. The IR spectrum is indicative
of a C=O carbonyl group and the 13C NMR peak at 206 ppm is consistent with this.
The 1H NMR spectrum indicates one CH, and one CH3 group, with a chemical shift of 2.4,
characteristic of a –(C=O)–CH3 group. Neither of these NMR signals is split so these groups are
32
not adjacent to each other. Putting all the data together, there is only one possible structure, 1,1-
diphenyl-2-propanone, as illustrated below in Figure 5, with chemical shifts as indicated.


Figure 5: 1,1-diphenyl-2-propanone with 1H chemical shifts, as indicated (left) and
13C chemical shifts, as indicated (right).