Secondary Secondary Science

Chemical Anniversaries: Celebrating Nobel Prize Winners

The 2017 Nobel Prize winners will be announced tomorrow, so it is a good time to look back at some previous winners with particular anniversaries this year.

One hundred years ago the First World War was into its fourth year. With most of the industrialised countries involved and the deaths counted in the millions it is not surprising that no Nobel prizes were awarded in 1917.

In a flash

Jumping to fifty years ago, the Nobel Prize of 1967 was awarded in two halves. One half went to Manfred Eigen, a German chemist, and the other half to the British pair, Ronald G.W. Norrish and George Porter. All three had investigated what happens during chemical reactions. Eigen used ultrasound to set off reactions.

Ronald Norrish was 48 and Professor of Physical Chemistry at Cambridge University when he took on George Porter as a postgraduate student in 1945. Norrish spent all his adult life at Emmanuel College, except for three years when he had fought in the First World War and had been a prisoner of war. He had grown up in Cambridge where his father was a pharmacist in a Boots the Chemist shop. Forty-eight is quite old for someone to embark on their Nobel prize-winning research. George Porter, however was keen to use his wartime experience working on radar to restart his chemistry career. He was born in Yorkshire in 1920 and had graduated from the University of Leeds in 1941.

Porter and Norrish developed a flashlight to investigate photochemical reactions. These are reactions that need light to start them off. The light causes bonds in the reacting molecules to break and form free radicals – atoms or molecules with a single spare electron. Radicals soon react with other molecules to form the products.  A typical photochemical reaction is that which destroys ozone in the stratosphere. Sunlight starts a chain of reactions that produces chlorine radicals from CFCs used in fridges and aerosols before they were banned in the 1980s.

The flashlight wasn’t used like a camera flash that illuminates a scene so that a photograph can be taken. Instead it was to kick-start a reaction. The flash of light that Porter and Norrish’s lamp produced had to last less time than the radicals that were formed took to react – less than a nanosecond. With their flashlight, they had the opportunity to collect data on the structure of the radicals which had never been done before.

Porter worked with Norrish until 1954. Then, for a few months, he used his method, called flash photolysis, in research on dyes for the British Rayon Research Association. In 1955, he was appointed Professor of Physical Chemistry at the University of Sheffield. Later, Porter became Director of the Laboratory of the Royal Institution where he continued his research. He was also eager to encourage young people to take up science as a career. He frequently appeared on television, particularly on Science Fair (later Young Scientists of the Year) in which teams of sixth form science students presented research they had done.

Flash photolysis is still an important tool for chemists and has had a part in several Nobel prizes since 1967. Now, however, the light is provided by lasers rather than a flashlight and can produce flashes that last less than a femto-second. Ronald Norrish died, in Cambridge, in 1978, and George Porter, who was made a Lord in 1990, died in 2002.

Images in a mirror

2017 is the centenary of the birth of John Cornforth who was awarded a Nobel Prize in 1975. Cornforth was born in Sydney, Australia. At the age of ten he developed an ear condition that over ten years turned him completely deaf. Despite being unable to hear the lectures, he nevertheless, completed a degree in Chemistry at Sydney University by the time he was 17. He won one of two scholarships to carry out research at Oxford University with the Nobel Prize winner, Robert Robinson.  The other scholar was Rita Harradence. They travelled to the UK in 1939, just as WWII began. As they worked together on the process for making compounds called steroids, their relationship became closer. John and Rita were married in 1941. When they had finished the work for their doctorates they joined Robinson’s team for a big war project – manufacturing penicillin.

After the war, both the Cornforths joined the National Institute for Medical Research, again working with Robinson. They returned to the study of sterols, in particular cholesterol. There is a lot of interest in the “good” and “bad” forms of cholesterol as they appear to aid and harm the heart and circulatory system. John and Rita investigated the chemical reactions that produce cholesterol in the body. These reactions involve enzymes which act as a “lock” to the “keys” of the smaller molecules which are joined together. To follow the reactions, it helped if the reacting molecules were asymmetric. This is when four different groups are attached to a central carbon atom i.e. C(abcd). The two ways of arranging the four groups are mirror images of each other but they cannot be superimposed on top of each other – just like your left and right hands. Often the small reacting molecules such as citric acid, have two groups the same i.e. C(aabc) so they are not asymmetric.

In 1962 John and Rita and their collaborator, George Popjak, moved to the Milstead Laboratory run by Shell Research. There they replaced the hydrogen atoms in one of the similar groups in the reacting molecules with deuterium or tritium (isotopes of hydrogen). This made the molecules asymmetric and enabled them to follow what happened when the molecules reacted in the enzyme. By this method they could work out the steps in the formation of cholesterol and other compounds. Rita worked alongside John on all his research and both their names appear on 41 research papers.

The 1975 Nobel Prize for Chemistry was shared between John Cornforth and Vladimir Prelog who was born in Sarajevo, Bosnia and did similar research. There was no recognition of the contribution made by Rita, except by John in his acceptance speech. Rita died in 2012 and John a year later. They had been married and chemical partners for over seventy years.

Activities

  1. Why wasn’t the Nobel Prize awarded in 1917?
  2. How long are a nano- and a femto-second?
  3. Why was the duration of the flash so important in George Porter’s research?
  4. Ronald Norrish guided many young researchers through their first postgraduate projects, yet flash photolysis is largely associated with George Porter. Do you think Norrish or Porter deserved more or less of their share of the Nobel Prize?
  5. Why is it important to find out how molecules such as cholesterol are formed?
  6. What effect does replacing hydrogen atoms with deuterium or tritium atoms in molecule have?
  7. Build models of molecules with four groups attached to a central carbon atom. Show that the groups must be different to produce mirror image molecules that are different.
  8. Except for a few short breaks to have children Rita Cornforth worked with her husband throughout their careers yet she did not receive a share of his Nobel Prize. Can you think of any reasons for this?
  9. Explore the winners of the Nobel Prize for Chemistry. How many were won by British chemists or chemists working in Britain? Which other nations have prize winners? How many women have won the Nobel Prize for Chemistry and what are their names?

Bibliography

1          “The Nobel Prize in Chemistry 1967”. Nobelprize.org. Nobel Media AB 2014. Web. 10 Sep 2017. http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1967/

2          “The Nobel Prize in Chemistry 1975”. Nobelprize.org. Nobel Media AB 2014. Web. 10 Sep 2017. http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1975/

3          https://en.wikipedia.org/wiki/Rita_Harradence

4          Oxford Dictionary of Scientists, OUP 1999.

 

Peter Ellis

Collins Secondary

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