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Addressing the points raised by my PhD research


The surprising results of our boron trifluoride experiments
Norman Greenwood Scientist
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So we did that, we made apparatus and did experiments. Having talked about an experiment we’d go in, do the experiment, go home, work up the results, have another conference, go in and do it... and people were amazed at the apparently short time we spent in the lab getting results of experiments which always seemed to work, and piling up huge amounts of results. But it was an interesting time, and we actually had to do some quite serious thinking about it and also some experimental design, because when you think about conductivity you have to find out how to change the electrical conduction which you are measuring into the amount that the compound is ionising. When the two compounds come together they don’t stay as covalent – there’s a redistribution of the electric charge, and that sometimes means that an ion splits off a charged particle, and that’s of course the interesting part for organic chemistry.

And so we had to find out to what extent this would happen. And it happened, we found out, anywhere between about one part in 10,000 and 100%. So it was... the 100% was with water, actually, but that was a large range. But when you get down to the detailed theory, which I won’t attempt to describe here, you find that as well as the conductivity you need the density of the liquid, and the viscosity, and with these you can do a temperature plot, you can get activation energies out, you can work out with theories that we developed what the percentage of ionisation was to see if it might be useful. And, moreover, you could electrolyse the compound and have an anode and a cathode department, and analyse what was in them to see what the ions were. So it was really quite an important advance in things.

Now, two points in this. The first is that people were very surprised that these compounds actually conducted electricity, though they shouldn’t have been, and the second was that in the ones that were highly ionised, some very interesting new experiments could be done.

Norman Greenwood (1925-2012) was born in Australia and graduated from Melbourne University before going to Cambridge. His wide-ranging research in inorganic and structural chemistry made major advances in the chemistry of boron hydrides and other main-group element compounds. He also pioneered the application of Mössbauer spectroscopy to problems in chemistry. He was a prolific writer and inspirational lecturer on chemical and educational themes, and held numerous visiting professorships throughout the world.

Listeners: Brian Johnson

Professor Brian FG Johnson FRS, FRSE, FRS Chem, FAcad Eu, FAS. Professor of Inorganic Chemistry University of Edinburgh 1991-1995, Professor of Inorganic Chemistry University of Cambridge 1995-2005, Master Fitzwilliam College Cambridge 1999-2005. Research interests include studies of transition metal carbonyls, organometallic chemistry, nano- particles and homogeneous catalysis. Professor Johnson is the author of over 1000 research articles and papers.

Tags: experiment, boron triflouride, conductivity, organic chemistry

Duration: 2 minutes, 42 seconds

Date story recorded: May 2011

Date story went live: 25 November 2011