Fullerene chemistry

In December 1991 the journal, Science, which is highly respected by top scientists around the world, announced the winner of its annual award of 'Molecule of the Year'. This title is given to the scientific development during the previous twelve months that is deemed to have exemplified quintessential scientific endeavour.

The 1991 winner was a molecule called buckminsterfellerene, or C60. The discovery of this elegant and remarkable molecule is a story of excitement, serendipity and inquisitiveness. It illustrates beautifully how the scientific process works and shows how even well established ideas can be modified by a new and unexpected discovery. The discovery of buckminsterfullerene, which is a form of pure carbon, has unveiled a novel type of molecule together with a brand new field of chemistry. Before buckminsterfullerene was known, carbon was thought to exist in only two naturally occurring crystalline forms: diamond and graphite. Other, non-crystalline forms, such as soot, are also known.

Many scientists were quite taken aback when, in 1985, buckminsterfullerene was discovered and found to be a third form of crystalline carbon. Since then, many other molecules related to buckminsterfullerene have been discovered or made: they all belong to a class of substances called fullerenes To many chemists, fullerenes are far more interesting and exciting than graphite or diamond. These substances could lead to the production of hundreds, even thousands, of novel substances with chemical and physical properties never before seen.
The future of fullerenes could well involve the manufacture of a variety of substances, including new synthetic polymers, industrial lubricants, superconductors, molecular computers and medically useful drugs.
The discovery of buckminsterfullerene is reminiscent of the proposal of the ring structure of benzene by the German chemist, Friedrich Kekule (1829-1896), in 1865.

Chemists at the time knew how many carbon and hydrogen atoms a benzene molecule had (six of each), but they were at a loss to explain how these atoms were arranged. Faraday had first discovered benzene in 1825, and the German chemist, Johann Loschmidt (1821-1895), later suggested that the benzene molecule was cyclical.

However, it was Kekule who finally proposed the proper structure of benzene. Kekule reputedly had a dream in which he saw a string of six carban atoms turn into a snake. The snake bit its tail, forming a ring. Soon afterwards, Kekule proposed the six-carbon ring structure of benzene, opening up a whole new area of chemistry ('aromatic chemistry') that led to many of today's synthetic substances, from dyes to drugs.

If Kekule's revelation is considered to be the beginning of the chemistry of ring compounds, buckminsterfullerene can be said to herald the dawn of 'sphere' chemistry.

Fullerene chemistry has it roots in research that was being carried out in the field of astronomy. The scientists involved in the discovery of buckminsterfullerene were initially interested in the chemicals present in the dust that surrounds and occurs in between stars.

If the diverse benefits that are predicted to arise from fullerenes are forthcoming, and there is every reason to be confident that they will be, then buckminsterfullerene will be a supreme example of how basic research into the stars of the cosmos can produce medically and industrially valuable substances.

In order to appreciate the context in which buckminsterfullerene was discovered, it is useful to have some understanding of the molecular structure of the two other crystalline forms of carbon, namely diamond and graphite.

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Kekule von Stradonitz ,(Friedrich) August

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