One of the greatest pioneers in radioactivity and radiochemistry, German chemist Otto Emil Hahn was awarded the 1944 Nobel Prize in Chemistry for his phenomenal discovery of nuclear fission. He was an experimental chemist of such eminence that before he actually became a Nobel Laureate, he had been nominated for the Nobel Prize in Chemistry for a record 22 times, and 16 times for the Nobel Prize in Physics!

Hahn’s historic discovery that the nucleus of atoms could be split, followed by a number of other important discoveries made a few years earlier. In 1932, James Chadwick discovered the neutron, offering researchers a powerful new tool for investigating atoms. In 1934, Irène Joliot-Curie and her husband Frédéric Joliot-Curie discovered artificial radioactivity. Soon afterwards, Enrico Fermi successfully bombarded over 60 elements with neutrons including the nuclei of the heaviest natural element Uranium. Keenly interested in Fermi’s work, Hahn, along with his long-time collaborator in research Prof. Lise Meitner, and his student Fritz Strassmann began to further research the bombardment of uranium nuclei, leading to the discovery of what came to be called nuclear fission.

Earlier, Hahn had also discovered a number of radioactive elements, but significant among these, especially from the oncology point of view, was his discovery of mesothorium-1 (Radium-228), a radioactive element that cost half as much to manufacture as Radium-226 that had been discovered by Pierre and Marie Curie, but was equally effective for use in radiation therapy for cancer patients. This discovery won Otto Hahn his first nomination for the Nobel Prize in Chemistry in 1914. He didn’t win it that year, but mesothorium began to be widely used for treating all types of cancer.

One of the many greats emerging from Sir Ernest Rutherford’s group, Hahn’s claim to fame came even before he joined the famed physicist in 1906. During a short stint with another celebrated chemist Sir William Ramsay, he discovered what he thought was a new radioactive element. He called it radiothorium. This was in fact a new isotope of thorium, though the concept of isotopes had not yet been introduced then, being first suggested by Frederick Soddy in 1913. But, Hahn’s discovery set the stage for the discovery and study of radio isotopes.

Early Life

Otto Emil Hahn was born in Frankfurt-on-Main, Germany, on 8 March, 1879. His father Heinrich was a successful glazier. His mother Charlotte came from a family of merchants. Having developed an interest in chemistry while in high school, Hahn pursued further studies in this subject at the German Universities of Marburg and Munich.

In his autobiography, Hahn wrote that during his college days he often spent more time in the beer halls than in studying, regretting that he didn’t pay more attention to physics and mathematics then. But, obviously, he did give enough time to studying chemistry for he got his doctorate in organic chemistry in 1901 from Marburg with Theodor Zincke as his doctoral supervisor.

After completing his one year of military service, Hahn returned to Marburg to serve as assistant to Professor Zincke. Being interested in becoming an industrial chemist, he knew that a recommendation from Zincke would make it easier for him to get a job in a major chemicals company. After two years, in 1904, when Hahn wanted to go to England to improve his grasp on English, Zincke helped him get a job as an assistant in Ramsay’s laboratory at University College, London. Working under Ramsay for a year, Hahn discovered the thorium isotope, and also developed an interest in radiochemistry, an underexploited field at that time. Encouraged by Ramsay, he changed his mind about a career in industry, deciding to persist with research on radioactivity instead.

In 1905, on Ramsay’s recommendation, Rutherford asked Hahn to join him at McGill University in Montreal, Canada. Here, Hahn discovered other new radioactive isotopes before returning to Germany and joining Emil Fischer’s institute at the University of Berlin in 1906, rising quickly through the faculty ranks to become a Professor of Chemistry.

In search of a collaborator for pursuing research on radioactivity, Hahn met and teamed up with the Austrian-born physicist Lise Meitner soon after returning to Germany, commencing a collaboration and friendship that would last for over three decades. Within five years Hahn’s research group moved to the new Kaiser Wilhelm Institute for Chemistry at Berlin-Dahlen where Hahn was made the head of the department of radiochemistry. Soon afterwards, World War I broke out. Hahn served in the German gas warfare service as a chemical warfare specialist, while Meitner volunteered as an X-ray nurse for the Austrian army.

When the war ended, Hahn and Meitner resumed their research work and in 1917 discovered protactinium (meaning ‘mother of actinium’), the till then missing element between thorium and uranium whose existence Mendeleev had predicted in 1871. The protactinium-231 that they discovered was a much longer-lived isotope (half-life 32,670 years) of protactinium than the one discovered in 1913 by Fajans and Göhring (protactinium-234 having half-life of just 1.17 minutes). During the 1920s, Hahn and Meitner were unsuccessfully nominated many times by several scientists for their discovery of protactinium.

In 1929, the brilliant young chemist Strassmann, just 27 years old then, joined the Kaiser Wilhelm Institute. And when Hahn decided to focus his attention on Fermi’s work, Strassmann joined him and Meitner in studying the decay patterns of the products created by the neutron bombardment of uranium nuclei.

Discovery of nuclear fission

In 1938, with the Nazis beginning to persecute all people of Jewish ancestry, Meitner fled from Germany with Hahn’s help and moved to Sweden. Hahn and Strassmann continued with their radioactivity experiments on uranium, but their work threw up perplexing results. The general belief then was in accordance with what Fermi had concluded—that following neutron bombardment of uranium, the products would be elements with atomic weights close to or greater than that of uranium. And so, Hahn had thought the radioactive transmutation products resulting from their experiments could be radium isotopes. But, he and Strassmann found that one of the products they got, seemed to be a radioactive form of the much lighter element barium. Hahn wondered how uranium could have transmuted into a much lighter element. The heavy nucleus of uranium would have to be split to produce something like that. Despite his long years of experience in research work, being a chemist, Hahn was hesitant about announcing something revolutionary related to physics.

So, he sent a detailed letter to Meitner in December 1938. He wrote: “… we are more and more coming to the awful conclusion that our Ra isotopes behave not like Ra, but like Ba. … Perhaps you can suggest some fantastic explanation. We ourselves realise that it can’t really burst into Ba.” He referred to the possible splitting of the uranium atom as “bursting”. Meitner replied that such a “bursting of the uranium nucleus” was hard to accept, but was possible.

A month later, further evidence related to barium, made Hahn almost certain his experiments had produced lighter elements. He published an article in the peer-reviewed monthly scientific journal Naturwissenschaften (The Science of Nature) asserting the same.

In the meanwhile, Meitner and her nephew, the young physicist Otto Frisch, used physics calculations to theoretically understand the baffling results of Hahn’s work and correctly interpreted that the uranium nucleus had indeed been split into lighter atoms, naming the phenomenon “fission”.

Scientists the world over realised the tremendous implications of Hahn’s discovery. Before World War II broke out, the German authorities set up a group to study the possible military applications of nuclear fission. Hahn was relieved that he was excluded from this group and allowed to continue with his own research work.

But, despite not being involved with Germany’s Nuclear Energy Project, Hahn was taken into custody by the Allied forces along with some other leading German scientists and interned in England at Farm Hall, Godmanchester, from July 1945 until January 1946. During his forced stay in England, Hahn kept himself fit by going on a daily run. It was here that he and the other German scientists learned about the atom bombs dropped on Hiroshima and Nagasaki in August 1945. Hahn was completely devastated that his discovery of fission had made it possible to construct the atom bomb and felt he was responsible for the loss of thousands of innocent lives. According to those who held him captive, “With the help of considerable alcoholic stimulant, he was calmed down.”

Hahn was still at Farm Hill when in November 1945 he learned from the Daily Telegraph newspaper that he had been awarded the Nobel Prize in Chemistry for 1944. Being refused permission by his captors to attend the prize ceremony, he attended the one held the following year in December 1946 after returning to his homeland earlier that same year.

Honours and acclaim

In 1948 Otto Hahn was elected President of the former Kaiser Wilhelm Society, newly renamed as the Max Planck Society. Honours and awards continued to be bestowed on him from all parts of the world. Just a list of such recognitions would run into pages. Across Europe and elsewhere, streets, squares, schools, institutes, and bridges were named after him and many medals and prizes declared in his name. As for the 1944 Nobel Prize, when it was announced, some scientists felt that injustice had been done to Meitner and that she too should have got it along with Hahn. But, Meitner said Hahn “fully deserved the Nobel prize in Chemistry”, and later, in a TV interview in 1959, commented on his discovery of fission saying, “Hahn and Strassmann were able to do this by exceptionally good chemistry, fantastically good chemistry, which was way ahead of what anyone else was capable of at that time.”

In 1966 however, Hahn, Meitner, and Strassmann were honoured with the prestigious Enrico Fermi Award. In 1959, the Otto Hahn Institute in Mainz and the Hahn-Meitner-Institute for Nuclear Research (HMI) were thrown open in Berlin. In 1964, the only nuclear-powered civilian ship in Europe was named the NS Otto Hahn. To honour Hahn for his special contribution to German-Israeli relations, in 1974, a wing of the Weizmann Institute of Science in Rehovot, Israel, was named after him.

Unfortunately, tragedy struck Hahn’s family in 1960 when his only son, Hanno—a reputed art historian, and his daughter-in-law Ilse, were killed in an automobile accident. Hahn and his wife never really recovered from this terrible shock. Otto Hahn died on 28 July, 1968 after a fall. His wife passed away just two weeks later.

Advocate of world peace and social responsibility

Convinced that it was a crime to use nuclear energy for developing weapons of war, Otto Hahn began campaigning against further development and testing of nuclear weapons after the war ended. He also initiated the Mainau Declaration of 1955 to highlight the dangers of atomic weapons and in 1959 co-founded the Federation of German Scientists, a non-governmental organisation committed to upholding the ideal of responsible science.
Hahn underscored the inherent dangers of a nuclear arms race and the radioactive contamination of planet Earth through light verse writer Ethel Jacobson’s rhyme:

• To smash the simple atom
• All mankind was intent
• Now any day
• The atom may
• Return the compliment.

References

1. NobelPrize.org: Otto Hahn – Biographical – Nobel Media AB 2014, https://www.nobelprize.org/prizes/chemistry/1944/hahn/biographical/
2. Robert Spence: Otto Hahn – Encyclopaedia Britannica, 16 March, 2018, https://www.britannica.com/biography/Otto-Hahn#ref5260
3. The New York Times: Not Forgotten – nytimes.com, 28 July, 2016, https://www.nytimes.com/interactive/projects/cp/obituaries/archives/otto-hahn
4. Atomic Heritage Foundation: Otto Hahn – atomicheritage.org, https://www.atomicheritage.org/profile/otto-hahn
5. Science History Institute: Otto Hahn, Lise Meitner, and Fritz Strassmann – Sciencehistory.org, 7 December 2017, https://www.sciencehistory.org/historical-profile/otto-hahn-lise-meitner-and-fritz-strassmann
6. M. Sgantzos, G. Kyrgias, et al: Otto Hahn (1879-1968): Pioneer in radiochemistry and discoverer of radiotherapeutic mesothorium – Journal of Balkan Union of Oncology, 19(3): 866-869, July 2014
7. Complete Dictionary of Scientific Biography: Hahn, Otto – Encyclopedia.com, 11 Sep. 2018, https://www.encyclopedia.com/people/science-and-technology/chemistry-biographies/otto-hahn
8. ChemViews Magazine: 50th Anniversary: Death of Otto Hahn – chemistryviews.org, 28 July 2018, https://www.chemistryviews.org/details/ezine/11077587/50th_Anniversary_Death_of_Otto_Hahn.html.

A few times in the history of chemistry have new synthetic methods been deemed so important that the originators have been awarded the Nobel Prize.” This is how the magnitude of the research work of the winners of the Nobel Prize in Chemistry for 1979 was emphasized in the Award Ceremony Speech. The England-born American chemist Herbert Charles Brown and the German chemist Georg Wittig had been awarded the Nobel prize that year for the innovative development of boron and phosphorous compounds, respectively, into important reagents for use in organic synthesis.

Choosing to work on the often-ignored element boron, Herbert Brown discovered borohydrides and organoboranes that gave chemists, to quote from the Award Ceremony Speech again, “new and powerful tools for organic synthesis”. Today, organoboranes have become the most versatile reagents in organic synthesis. Brown created over 50 combinations of boron and hydrogen that proved to be invaluable for manufacturing pharmaceuticals and other biological compounds that would have otherwise been difficult to synthesize. Boranes are currently used for synthesizing important medications such as the cholesterol-lowering drug Lipitor, and the antidepressant Prozac.

Early Years

Brown’s early years were marked by hardship. Born Herbert Brovarnik (Brown being an anglicised form of his original surname) on 22 May 1912 in London to Ukrainian immigrant parents, he was just a toddler when his family moved to Chicago in June 1914. His father, who ran a hardware store, passed away when he was 14. So, he had to drop out of school for a few years to run the store though he excelled in studies and had been allowed to skip several grades. After his mother took over the running of the family store, he was able to resume his school education and finally completed it in 1930.

To support the family, he did a few odd jobs for a while before starting his college education at Crane Junior College. But, no sooner he began his studies there than it was announced the institution was likely to close. So, he shifted to night school and funded his education by working part-time as a shoe clerk. Luckily for him, one of the instructors at Crane decided to let some students use his lab and complete their education on their own, and Brown happily accepted the offer. That’s when he met his future wife Sarah Baylen, the brightest chemistry student at the lab before he joined the group. The two of them and a few other students then moved to Wright Junior College. When they completed their course here in 1935, his girlfriend Sarah had scribbled a message in his yearbook, beginning with: To a future Nobel Laureate. Prophetic words that later on came true. That same year, Brown joined the University of Chicago from where he earned a B. S. degree in 1936, completing the two-year course in one year.

Interest in boron chemistry – a stroke of serendipity

As a graduation gift, Sarah, who had also joined the University of Chicago, gave Brown a copy of Alfred Stock’s book—The Hydrides of Boron and Silicon. Running short of cash, she had picked this book because at $2 it was the cheapest one in the University bookstore! However, it was this gift that peaked Brown’s interest in an obscure subject like the hydrides of boron. Deciding to choose it for his Ph.D. thesis, he studied with Professor H.I. Schlesinger who taught at the University of Chicago and was a well-known chemist actively engaged in this area of research.

The very next year, in 1937, Herbert married Sarah. He was then earning a meagre $400 a year as a graduate assistant from which he had to pay $300 for his tuition fees. But with Sarah obtaining a position at Billings Hospital in Medical Chemistry, they somehow managed to make ends meet. Brown got his Ph.D. in 1938, and being a married man now, tried in vain to find a job in the industry. Finally, he accepted the postdoctoral position offered by Professor M. S. Kharasch at a stipend of $1600, and that was how his academic career began. Out of necessity. When honoured with the Nobel Prize, he had famously said: “I am an unusual example of a chemist who ended up in academic work because he could not find an industrial position.”

One year later, Professor Schlesinger invited him to become his research assistant with the rank of instructor. This job gave him the opportunity to research methods of preparing lithium and sodium borohydrides and other related borohydrides, and studying their reactions. The compound sodium borohydride, NaBH4, that he and his Ph.D. and postdoctoral mentor Schlesinger discovered was used to generate hydrogen gas for weather balloons during World War II. It also has multiple applications today including the manufacture of different antibiotics, as a bleaching agent in the dyeing industry, and as a reducing agent in the synthesis of gold nanoparticles.

In 1947, Herbert Brown joined Purdue University in West Lafayette, Indiana, as professor of inorganic chemistry. In 1959, he was promoted to the position of R. B. Wetherill Professor and in 1960 to R. B, Wetherill Research Professor. When he retired in 1978, he acquired the status of R. B. Wetherill Research Professor Emeritus. He retained this position till his death in 2004.

Meritorious achievements

The fortuitous gift of a cheap chemistry-related book motivated Brown to focus on boron for his Ph. D. research, and also led him to an area in chemistry for which he developed a lifelong attachment.

During the 1950s, he and his team of graduate students and post-doctoral researchers discovered that the simplest compound of boron and hydrogen, diborane, easily reacts with unsaturated organic molecules to produce organoboranes. He then carried out extensive research on organoboranes and on the reduction of different organic compounds with sodium borohydride, other related borohydrides, and aluminohydrides. His research work revolutionised many areas of chemistry, including synthetic organic chemistry, the compounds he discovered drastically reducing the time required for synthesising new compounds that could potentially be used as drugs, many of them directly leading to the successful manufacturing of important drugs such as hydrocortisone, steroids, and prostaglandins.

Brown mentored a large number of students and researchers. He would repeatedly urge his team members to refrain from spending more than eight hours a day in the laboratories. Instead, he stressed the value of sound thinking, planning, preparation, and execution of laboratory experiments, and timely interpretation of the results. The celebrated Japanese chemists Ei-ichi Negishi and Akira Suzuki, both 2010 Nobel Laureates in Chemistry, studied with Brown in the 1960s.

Herbert Brown held dozens of patents. During the course of his illustrious career spanning around seven decades, he published almost 1300 scientific publications, including a number of books, authoring on an average around 20 publications a year.

Brown’s many achievements were internationally acknowledged by way of a slew of awards. He was awarded the Nichols Medal for 1959, the ACS Award for Creative Research in Synthetic Organic Chemistry for 1960, the Linus Pauling Medal for 1968, the National Medal of Science for 1969, the Roger Adams Medal for 1971, the Charles Frederick Chandler Medal for 1973, the Madison Marshall Award for 1975, among others, and of course, the Nobel Prize for 1979.

He was elected to the National Academy of Sciences in 1957 and the American Academy of Arts and Sciences in 1966. He received an honorary Doctorate of Science degree from the University of Chicago in 1968, was an honorary member of the International Academy of Science, a member of the American National Academy of Sciences, honorary fellow of the Chemical Society (London), and a foreign member of the Indian National Academy of Sciences. He was inducted into the Alpha Chi Sigma Hall of Fame in 2000.
Besides, the Herbert C. Brown Laboratory of Chemistry at Purdue University has been named after him.

Herbert and Sarah generously provided a number of endowments – the ACS Herbert C. Brown Award for Creative Work in Synthetic Methodology, the Herbert C. Brown Lectures in 1983, the Herbert C. Brown Distinguished Professorship in 1998, and the Herbert C. Brown Center for Borane Research in 1998, to name a few.

Herbert Charles Brown died at the age of 92 on 19 December 2004 of a heart attack at a hospital in West Lafayette. Sarah died a few months later on 29 May 2005 at the age of 89. Interestingly, Brown’s distinguished one-time assistant Ei-ichi Negishi had visited him at his home barely 10 hours before he died to discuss an urgent chemistry-related matter. Negishi said, “For his age he appeared well, showing no sign of his sudden death the next morning.”

After Brown passed away, a biography issued by Purdue University lauded him for having discovered ‘a new continent in chemistry, a continent that will take many years of enthusiastic research effort to explore in detail and exploit for the good of mankind’.
His wife Sarah had sort of predicted decades earlier that he would someday be a Nobel Laureate. But, Brown not only achieved this distinction, he also rose to the stature of a trailblazing giant in the fields of organic and organoboron chemistry and came to be acknowledged as one of the foremost American chemists of the 20th century.

References

1. Nobelprize.org: Herbert C. Brown – Biographical – Nobel Media AB 2014, https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1979/brown-bio.html
2. Editors, Biography.com: Herbert C. Brown Biography – Biography.com, 2 April 2014, https://www.biography.com/people/herbert-c-brown-9228287
3. Mitch Jacoby: Herbert C. Brown Dead At Age 92 – Chemical & Engineering News, 21 December 2004, http://pubs.acs.org/cen/news/8251/8251brown12_23.html
4. Ei-Ichi Negishi: Herbert Charles Brown 1912 – 2004: A Biographical Memoir – National Academy of Sciences, 2008.
5. Purdue University, Department of Chemistry: Herbert C. Brown: 1979 Nobel Prize in Chemistry – https://www.chem.purdue.edu/hcbrown/
6. Editors, TheFamousPeople.com: Herbert C. Brown Biography – TheFamousPeople.com, 31 October 2017, https://www.thefamouspeople.com/profiles/herbert-c-brown-7571.php
7. Bea Perks: Obituary: Herbert C. Brown – Chemistry World, 1 February 2005, https://www.chemistryworld.com/news/obituary-herbert-c-brown/3003031.article.