Allotropes of Carbon
• Allotropes are different structural forms of the same _________________.
• Carbon can arrange it’s electrons in different ways to form these allotropes:
3. Nanoparticles – e.g. ___________________ and _________.
• Diamonds are _______ and ____________________
and ____________________ (they sparkle).
• Each carbon atom has ___ strong covalent bonds to __
other carbon atoms. They make the structure very
• Diamond is the ________________ natural substance
due to the 4 strong covalent bonds.
• 4 strong covalent bonds from every carbon atom also mean
that the melting point is very _________ because the
bonds would have to be ______________ and this takes
a lot of energy.
• Diamonds are ____________________ in water.
• Diamonds do NOT conduct electricity (they have no free e-)
1. Diamond is used to make cutting tools because
2. Diamonds are used to make jewellery because
• Graphite is ____________ and _____________ but also quite ____________
• Each carbon atom forms just ____ strong covalent bonds.
• Graphite forms sheets (layers) of carbon atoms.
3 layers of carbon sheets
• The unbonded electrons sit between the layers and loosely hold them together with
• This means the layers are very ___________ to separate and they __________
over each other making it ________________________.
• Graphite is insoluble in water
• The 3 covalent bonds take a lot of energy to break so graphite has a __________
• Graphite can conduct electricity because the electrons between the layers are
THERE IS A SEPARATE SHEET FOR QUICK REVISION OF SOME OF THE ELECTROLYSIS THAT
WE HAVE COVERED SO FAR.
General revision of some electrolysis involving graphite (carbon) electrodes
1. General electrolysis cell
2. Electrolysis of Al2O3
3. Electrolysis of molten NaCl
Summary to compare Diamond and Graphite
• 4 strong ___________ bonds from • __ strong covalent bonds from each
each carbon to 4 other carbon atoms carbon to __ other carbon atoms
• no free ______________ to conduct • sheets of carbon atoms in layers held
electricity loosely together by ________ forces
• __________free to move and
Uses: cutting tools Uses: dry lubricant
Buckminsterfullerenes and Nanotubes
Also known as a Bucky Ball
• black solid
• deep red in solution in petrol
• Buckminster fullerene has the formula C60 i.e. it is made from 60 carbon atoms
The uses of fullerenes
• It is thought that fullerenes could be used to ‘cage’ other molecules. These ‘caged
molecules’ could then be used as drug delivery systems.
• The advantage is that they could be made to target specific areas of the body where
a drug is most needed. This is particularly useful if you have a drug that may be toxic
to other parts of the body e.g. in chemotherapy to cure cancerous cells.
• Alternatively they could be used to provide a slow release system for a drug
Fullerenes can be joined together to make nanotubes
Properties of Nanotubes:
1. very strong
2. electrical conductors
Uses of Nanotubes:
1. ________________________ in electrical circuits
2. _________________________ – nanotubes have a huge surface area on
which to attach the catalyst molecules. Increasing the surface area of the
catalyst means it is more efficient and this means more money can be made
in the same amount of time
3. To ______________________ graphite in tennis rackets
Chemistry versus Nanochemistry
1000 000 000 000 000 000 000 yottametre
zeta 1021 1000 000 000 000 000 000 000 zetametre
exa 1018 1000 000 000 000 000 000 exametre
peta 1015 1000 000 000 000 000 petametre
tera 1012 1000 000 000 000 terametre
giga 109 1000 000 000 gigametre
mega 106 1000 000 megametre
kilo 103 1000 kilometre
100 1 metre
milli 10−3 0.001 millimetre
micro 10−6 0.000 001 micrometre
nano 10−9 0.000 000 001 nanometre
pico 10−12 0.000 000 000 001 picometre
femto 10−15 0.000 000 000 000 001 femtometre
atto 10−18 0.000 000 000 000 000 001 attometre
zepto 10−21 0.000 000 000 000 000 000 001 zeptometre
yotto 10−24 0.000 000 000 000 000 000 000 001 yottometre
• Chemistry works with materials on a ________________ scale
e.g. grams, kilograms, tonnes, megatonnes
• Nanochemistry works with materials on an ______________ scale e.g. nanometres
Why is this important?
Nanoparticles have different properties to the ‘bulk’ chemical.
What is Molecular Manufacturing? (also known as molecular engineering)
Molecular engineering creates nanoparticles to a specific design. This can occur in one of
The discovery of buckminsterfullerene
Allotropy, organic chemistry, chemists
In 1985, virtually all school chemistry textbooks became out of date overnight. Prior to this, textbooks
stated that there were two allotropes of carbon – diamond and graphite. Allotropes are forms of the
same element which differ in the way their atoms are arranged. Diamond and graphite are classic
examples of allotropy. In diamond the carbon atoms are arranged tetrahedrally and in graphite they
form two-dimensional layers of interlinked hexagons.
Picture Diamond and graphite structures
In 1985 the discovery was announced of a third allotrope in which the atoms form C60 molecules in the
shape of a football. This led to the award of the 1996 Nobel Prize to Harry (now Sir Harry) Kroto of
Sussex University, Robert Curl and Richard Smalley (both of Rice University in Houston, USA).
Harry Kroto had an interest in molecules found in interstellar space which can be identified from their
microwave spectra – by comparing signals obtained from outer space with those measured for known
compounds in the laboratory. He was particularly interested in poly-ynes (molecules with several
carbon-carbon triple bonds) but these are difficult to make conventionally. In 1984, Kroto began
collaboration with Smalley and Curl in Houston who had an apparatus called AP2 (‘App-two’). This
used a laser to blast clusters of atoms off solid targets and then led the clusters into a mass spectrometer
where their relative molecular masses could be measured. Kroto hoped that if a graphite target were
used, small sections of graphite layers might rearrange themselves into poly-ynes whose spectra could
then be measured.
Clusters of carbon atoms were indeed formed, and unexpectedly large peaks were found in the mass
spectra with masses corresponding to C60 and (at a lesser intensity) C70. These peaks always appeared
together, and Kroto started to refer to them as the Lone Ranger and Tonto.
Why were these molecules so stable? Sheets of graphite in which the carbon atoms are arranged in
hexagons would be expected to be very unstable because they would have so many ‘dangling bonds’
with unpaired electron at the edges. Inspired by geodesic dome structures made up of hexagons
designed by the architect Richard Buckminster Fuller, the team began to consider the possibility that a
sheet of graphite hexagons might curl up into a spherical shape so that all the ‘dangling bonds’ could
link up. However, work with crude paper molecular models showed that this was impossible if all the
atoms were linked in hexagons. Kroto recalled a spherical ‘stardome’ made of cardboard shapes that he
had built for his children and believed that it contained pentagons. This was a vital clue. More late night
work with the paper models showed that a spherical shape could be made with 20 hexagons and 12
pentagons. A quick counting of bonds showed that this structure was chemically reasonable in that each
carbon atom was forming four covalent bonds – one double and two single. Having made the model, the
team did not know what the geometrical shape was and the story goes that a phone call to the chairman
of the Rice University Mathematics Department for advice elicited the reply ‘what you’ve go there boys
is a soccer ball’. However, Kroto remembers a less laconic reply.
‘We were sitting in Rick Smalley's office. We were extremely high, on a roll at the time as
you might imagine, only just recovering from the realisation
of what the bloody thing might be.
Jim Heath [a student of Smalley’s] and I and almost certainly Sean O'Brien [another student
of Smalley’s] and probably Bob Curl too were there. Rick was definitely not there at the
time and that is why Jim was sitting in Rick's chair at Rick's desk when the phone rang. Jim
answered it. Then a sort of stunned expression came over his face and Jim said ‘It's
soccerball’, or he may have said ‘He says it's soccerball’. I am pretty sure he did not say ‘It's
This appeared to be a return call from a mathematician that Rick must have called up earlier
in the day to ask what the structure might be.’
Picture The ‘soccerball’ structure of buckminsterfullerene
At this stage, the soccer ball structure (and a similar ‘rugby ball structure for C70) was no more than
inspired speculation. Confirmation had to wait until enough C60, now christened buckminsterfullerene
(buckminsterfuller after the architect and ene because it had double bonds), could be made to allow,
ultraviolet / visible, infrared and 13C NMR spectra to be measured as well as X-ray diffraction studies.
App-two produced only minute amounts of molecules at a time. Theorists predicted that a ‘soccer ball
structure’ should have just four lines in its IR spectrum (at specific wavelengths) and that its 13C NMR
spectrum should have just one line because all the carbon atoms are in exactly equivalent positions.
NMR is one of the most important techniques for organic chemists. The saying goes that ‘when the
NMR breaks down, the chemists go home.’
To produce enough buckminsterfullerene for these tests, a different approach was used. Two graphite
rods inside a bell jar containing an inert gas at low pressure were connected to an electrical supply, and
an electrical arc formed between the two electrodes (one experimenter described this apparatus as ‘a
battery and a pencil’).This produced a soot which was found to contain about 1% of a mixture of C60
and C70. These could be separated from the soot by sublimation or by extraction into benzene (in which
the soot was insoluble) and from each other by chromatography. At Sussex Kroto and his student
Jonathan Hare (now the presenter of TV programmes, Rough Science and Hollywood Science) together
with Roger Taylor and Abdul Sada were the first to measure the single line 13C NMR spectrum (Kroto
called it ‘the one line proof’). Wolfgang Krätschmer and Donald Huffman, working at the Max Planck
Institute for Nuclear Physics in Germany and in Arizona State University, extracted the molecule and
measured its X-ray pattern just ahead of the Sussex team and measured the IR and UV / visible spectra.
Both events occurred in 1990. Krätschmer and Huffman had in fact observed the UV / visible spectrum
some years earlier but without realising its significance.
This is a much simplified account both in detail of the actual experiments and the number of people,
and indeed research teams, working on buckminsterfullerene. There is a much more detailed but highly
readable account in J Baggott, Perfect Symmetry, Oxford: Oxford University Press, 1994. This was
written before the award of the Nobel Prize, of course. As well as the story of the discovery, it deals
with some of the chemistry and properties of the family of fullerenes and their derivatives. The Nobel
lectures of the three laureates are available at www.nobel.se.
Rick Smalley died in November 2005 after a long fight against leukaemia.