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Professor Athel Beckwith was interviewed in 2003 for the Interviews with Australian scientists series. By viewing the interviews in this series, or reading the transcripts and extracts, your students can begin to appreciate Australia's contribution to the growth of scientific knowledge.
The following summary of Beckwith's career sets the context for the extract chosen for these teachers notes. The extract discusses what free radicals are and how antioxidants are used to control them in living organisms. Use the focus questions that accompany the extract to promote discussion among your students.
Athel Beckwith was born in 1930 in Perth. He earned a BSc from the University of Western Australia in 1951. It was during his honours year at UWA that he began working on reaction mechanisms, trying to understand the rules that govern chemical reactions and how these rules might be used predictively. He received a DPhil from Oxford in 1956 for his work investigating how free radicals interact with organic compounds.
On returning to Australia in 1957 he worked for a time with the CSIRO Division of Industrial Chemistry, looking for commercial uses of wool wax. In 1958 he was appointed lecturer in chemistry at the University of Adelaide and in 1965 became Professor. His research during these years returned to free radicals, particularly their properties and behaviour as reactive intermediates in chemical reactions.
Beckwith left Adelaide in 1981 to take up a Chair in chemistry in the Research School of Chemistry at the Australian National University (ANU), where he remained until his retirement in 1996. His work there built on earlier findings and included synthesis of complex organic molecules. During this time he also served as Dean of the Research School of Chemistry at the ANU.
He was elected a Fellow of the Australian Academy of Science in 1973 and a Fellow of the Royal Society in 1987. He is also a Fellow and Past President of the Royal Australian Chemical Institute.
In 2004 Beckwith was appointed an Officer of the Order of Australia (AO) for service to science in the field of organic chemistry as a leading researcher and academic, and through the provision of advice to government and the wider community on scientific matters.
The transition to university teaching
Perhaps this is the time to ask you to explain what is meant by free radical chemistry.
Free radicals, in solution, were first described in 1900, by an amazing pioneer called Moses Gomberg. Chemists had tried for years beforehand to make free radicals without success and had concluded that they didn't exist. Then Gomberg announced that he had successfully generated them, and indeed we now know that he had. He is also famous for a memorable footnote to the first paper, which was published in 1900 in the American Chemical Society Journal. Having described these new species, these free radicals, he notes, 'This work will be continued and I reserve the field for myself.'
In fact, he needn't have worried, because nobody else was very interested. Most scientists didn't believe he had actually generated organic free radicals in solution. And even at the time that I was entering the field, there were still many chemists who had similar doubts. There were a great many polemical articles in the scientific literature, with some chemists maintaining that organic radicals can't exist in solution. Others were convinced that they could. There were very few people seriously working in the field of organic radicals in solution – a couple in Great Britain, a couple in America – I suppose six people, in all, in the world.
Free radicals are very reactive molecules. All the more familiar organic compounds, such as sugar, alcohol and acetone, are stable; they can be stored for long periods without change. They are stable because they possess an even number of electrons arranged in pairs. The bonds between the atoms consist of pairs of electrons; a pair of electrons is a stable arrangement. Furthermore, around most of the atoms in such molecules there are eight electrons in four pairs. This is a very stable configuration.
However, if one of the two-electron bonds in such a molecule is broken by irradiation of a sample with light or by otherwise applying energy then one of the ways a bond may break is by each half taking one electron. There will then be two new molecules each of which has an odd number of electrons. Inevitably one of those electrons must be unpaired and that is a very unstable state. These newly formed highly unstable, and hence highly reactive, molecules are free radicals.
Are there now two free radicals, or one?
If a bond in an ordinary stable molecule is broken symmetrically, two free radicals are generated. Each new molecule has an unpaired electron, and the formal description of a free radical is 'any atom or molecule that contains an unpaired electron'. Hence any species that has an uneven number of electrons must be a free radical. Indeed any species that has an even number of electrons but has, for some reason or another, has two of the electrons unpaired is also a free radical (a diradical).
Because free radicals have an unpaired electron, they are inherently extremely reactive. To return to a stable state the unpaired electron must couple with another electron to form an electron-pair. One of the great virtues of free radicals is that they will often react with organic molecules at positions that are normally resistant to attack.
Why don't we go rancid?
During your final years in Adelaide you went again to Oxford for some months, in 1979, and made some other visits while you were overseas. Why Oxford this time?
It was becoming increasingly clear that radicals are very important outside of the test tube as well as in it, and particularly in natural systems. One of the things I used to ask my students was, 'Why don't we go rancid?' It's a good question. Our bodies contain lots of fat. If one leaves a bit of fat lying out in the sun for a couple of days, it smells to high heaven. Why don't you and I go rancid? Well, we now know that fats go rancid because of free radical attack. Indeed, free radicals are everywhere. Whenever a chemical bond is broken by ultraviolet light, cosmic rays or beta radiation free radicals are formed. So radicals are ubiquitous. When they attack fats oxidative processes involving oxygen occur. The reason we don't go rancid is that we are protected while we are alive by natural anti-oxidants such as vitamin E and vitamin C. Because of this I became very interested in the mechanisms of metabolic reactions possibly involving the attack of radicals on the constituents of living organisms.
An edited transcript of the full interview can be found at http://www.science.org.au/scientists/interviews/b/ab.htm.
Focus questions
Chemically speaking, what is the difference between a stable molecule and a reactive one?
What are free radicals and how are they formed?
Select activities that are most appropriate for your lesson plan or add your own. You can also encourage students to identify key issues in the preceding extract and devise their own questions or topics for discussion.
antioxidants
chemistry
electrons
free radical
organic compounds
metabolic reactions
reactive intermediates
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