Herbert C. Brown

Herbert Charles Brown (May 22, 1912 – December 19, 2004) was an English-born American chemist and Nobel Prize in Chemistry laureate for his work with organoboranes.

Life and career

Brown was born Herbert Brovarnik in London, to Ukrainian Jewish immigrants from Zhitomir, Pearl (née Gorinstein) and Charles Brovarnik, a hardware store manager and carpenter.^[1] He moved to the United States in June 1914, at the age of two.^[2] In 1935 he left Wilbur Wright Junior College and that autumn entered the University of Chicago, completed two years of studies in three quarters, and earned a B.S. in 1936.^[2] That same year, he became a naturalized United States citizen.^[3] On February 6, 1937, Brown married Sarah Baylen, the person he credits with making him interested in hydrides of boron, a topic related to the work in which he with Georg Wittig won the Nobel prize in Chemistry in 1979.^[2] Two years after starting graduate studies, he earned a Ph.D. in 1938, also from the University of Chicago.

Unable to find a position in industry, he decided to accept an offer for a position as a post-doctorate. This became the beginning of his academic career. He became an instructor at the University of Chicago in 1939, and held the position for four years before moving to Wayne University in Detroit as an assistant professor. In 1946, he was promoted to an associate professor. He became a professor of inorganic chemistry at Purdue University in 1947^[4] and joined the Beta Nu Chapter of Alpha Chi Sigma there in 1960.^[5] He held the position of Professor Emeritus from 1978 until his death in 2004.^[2] The Herbert C. Brown Laboratory of Chemistry was named after him on Purdue University's campus. He was an honorary member of the International Academy of Science.

During World War II, while working with Hermann Irving Schlesinger, Brown discovered a method for producing sodium borohydride (NaBH₄), which can be used to produce boranes, compounds of boron and hydrogen. His work led to the discovery of the first general method for producing asymmetric pure enantiomers. The elements found as initials of his name H, C and B were his working field.

In 1969, he was awarded the National Medal of Science.^[6]

Brown was quick to credit his wife Sarah with supporting him and allowing him to focus on creative efforts by handling finances, maintaining the house and yard, etc. According to Brown, after receiving the Nobel prize in Stockholm, he carried the medal and she carried the US$100,000 award.

He was inducted into the Alpha Chi Sigma Hall of Fame in 2000.^[7]

He died December 19, 2004, at a hospital in Lafayette, Indiana after a heart attack. His wife died May 29, 2005, aged 89.

Research

Borane, BH₃, is a gaseous compound that is only present at high temperatures. It diamerizes to form diborane, B₂H₆. Diborane has a pair of three-center two-electron bonds.

As a doctoral student at the University of Chicago, Herbert Brown studied the reactions of diborane, B₂H₆. Hermann Irving Schlesinger's laboratory at the University of Chicago was one of two laboratories that prepared diborane. It was a rare compound that was only prepared in small quantities. Schlesinger was researching the reactions of diborane to understand why the simplest hydrogen-boron compound is B₂H₆ instead of BH₃.^[8]

A general reaction between diborane and a ketone

When Brown started his own research, he observed the reactions of diborane with aldehydes, ketones, esters, and acid chlorides. He discovered that diborane reacts with aldehydes and ketones to produce dialkoxyboranes, which are hydrolyzed by water to produce alcohols. Until this point, organic chemists did not have an acceptable method of reducing carbonyls under mild conditions. Yet Brown’s Ph.D. thesis published in 1939 received little interest. Diborane was too rare to be useful as a synthetic reagent.^[8]

In 1939, Brown became the research assistant in Schlesinger’s laboratory. In 1940, they began to research volatile, low molecular weight uranium compounds for the National Defense Research Committee. Brown and Schlesinger successfully synthesized volatile uranium (IV) borohydride, which had a molecular weight of 298. The laboratory was asked to provide a large amount of the product for testing, but diborane was in short supply. They discovered that lithium hydride reacts with boron trifluoride in ethyl ether, allowing them to produce diborane in larger quantities. This success was met with several new problems. Lithium hydride was also in short supply, so Brown and Schlesinger needed to find a procedure that would allow them to use sodium hydride instead. They discovered that sodium hydride and methyl borate reacted to produce sodium trimethoxyborohydride, which successfully replaced the lithium hydride.^[8]

Soon they were informed that there was no longer a need for uranium borohydride, but it appeared that sodium borohydride could be useful in generating hydrogen. They began to look for a cheaper synthesis and discovered that adding methyl borate to sodium hydride at 250° produced sodium borohydride and sodium methoxide. When acetone was used in an attempt to separate the two products, it was discovered that sodium borohydride reduced the acetone.^[8]

Sodium borohydride is a mild reducing agent that works well in reducing aldehydes, ketones, and acid chlorides. Lithium aluminum hydride is a much more powerful reducing agent that can reduce almost any functional group. When Brown moved to Purdue University in 1947, he worked to find stronger borohydrides and milder aluminum hydrides that would provide a spectrum of reducing agents. The team of researchers at Purdue discovered that changing the metal ion of the borohydride to lithium, magnesium, or aluminum increases the reducing ability. They also found that introducing alkoxy substituents to the aluminum hydride decreases the reducing ability. They successfully developed a full spectrum of reducing agents.^[8]

In hydroboration-oxidation, the OH group adds to the less-substituted carbon in the double bond.

While researching these reducing agents, Brown’s coworker, Dr. B. C. Subba Rao, discovered an unusual reaction between sodium borohydride and ethyl oleate. The borohydride added hydrogen and boron to the carbon-carbon double bond in the ethyl oleate. The organoborane product could then be oxidized to form an alcohol.^[8] This two-step reaction is now called hydroboration-oxidation and is a reaction that converts alkenes into anti-Markovnikov alcohols. Markovnikov's rule states that, in adding hydrogen and a halide or hydroxyl group to a carbon-carbon double bond, the hydrogen is added to the less-substituted carbon of the bond and the hydroxyl or halide group is added to the more-substituted carbon of the bond. In hydroboration-oxidation, the opposite addition occurs.^[9]

See also

• List of Jewish Nobel laureates

References

External links

• Herbert Brown biography at the Nobel Foundation from Les Prix Nobel, 1979
• Herbert Brown obituary in Chemical & Engineering News
• Herbert Brown obituary in USA Today
• National Academy of Sciences Biographical Memoir
• Nobel Lecture 1979

Laureates of the Nobel Prize in Chemistry 1901–1925 1901 Jacobus van 't Hoff 1902 Emil Fischer 1903 Svante Arrhenius 1904 William Ramsay 1905 Adolf von Baeyer 1906 Henri Moissan 1907 Eduard Buchner 1908 Ernest Rutherford 1909 Wilhelm Ostwald 1910 Otto Wallach 1911 Marie Curie 1912 Victor Grignard / Paul Sabatier 1913 Alfred Werner 1914 Theodore Richards 1915 Richard Willstätter 1916 1917 1918 Fritz Haber 1919 1920 Walther Nernst 1921 Frederick Soddy 1922 Francis Aston 1923 Fritz Pregl 1924 1925 Richard Zsigmondy 1926–1950 1926 Theodor Svedberg 1927 Heinrich Wieland 1928 Adolf Windaus 1929 Arthur Harden / Hans von Euler-Chelpin 1930 Hans Fischer 1931 Carl Bosch / Friedrich Bergius 1932 Irving Langmuir 1933 1934 Harold Urey 1935 Frédéric Joliot-Curie / Irène Joliot-Curie 1936 Peter Debye 1937 Norman Haworth / Paul Karrer 1938 Richard Kuhn 1939 Adolf Butenandt / Leopold Ružička 1940 1941 1942 1943 George de Hevesy 1944 Otto Hahn 1945 Artturi Virtanen 1946 James B. Sumner / John Northrop / Wendell Meredith Stanley 1947 Robert Robinson 1948 Arne Tiselius 1949 William Giauque 1950 Otto Diels / Kurt Alder 1951–1975 1951 Edwin McMillan / Glenn T. Seaborg 1952 Archer Martin / Richard Synge 1953 Hermann Staudinger 1954 Linus Pauling 1955 Vincent du Vigneaud 1956 Cyril Hinshelwood / Nikolay Semyonov 1957 Alexander Todd 1958 Frederick Sanger 1959 Jaroslav Heyrovský 1960 Willard Libby 1961 Melvin Calvin 1962 Max Perutz / John Kendrew 1963 Karl Ziegler / Giulio Natta 1964 Dorothy Hodgkin 1965 Robert Woodward 1966 Robert S. Mulliken 1967 Manfred Eigen / Ronald Norrish / George Porter 1968 Lars Onsager 1969 Derek Barton / Odd Hassel 1970 Luis Federico Leloir 1971 Gerhard Herzberg 1972 Christian B. Anfinsen / Stanford Moore / William Stein 1973 Ernst Otto Fischer / Geoffrey Wilkinson 1974 Paul Flory 1975 John Cornforth / Vladimir Prelog 1976–2000 1976 William Lipscomb 1977 Ilya Prigogine 1978 Peter D. Mitchell 1979 Herbert C. Brown / Georg Wittig 1980 Paul Berg / Walter Gilbert / Frederick Sanger 1981 Kenichi Fukui / Roald Hoffmann 1982 Aaron Klug 1983 Henry Taube 1984 Robert Merrifield 1985 Herbert A. Hauptman / Jerome Karle 1986 Dudley R. Herschbach / Yuan T. Lee / John Polanyi 1987 Donald J. Cram / Jean-Marie Lehn / Charles J. Pedersen 1988 Johann Deisenhofer / Robert Huber / Hartmut Michel 1989 Sidney Altman / Thomas Cech 1990 Elias Corey 1991 Richard R. Ernst 1992 Rudolph A. Marcus 1993 Kary Mullis / Michael Smith 1994 George Olah 1995 Paul J. Crutzen / Mario J. Molina / Frank Rowland 1996 Robert Curl / Harold Kroto / Richard Smalley 1997 Paul D. Boyer / John E. Walker / Jens Christian Skou 1998 Walter Kohn / John Pople 1999 Ahmed Zewail 2000 Alan J. Heeger / Alan MacDiarmid / Hideki Shirakawa 2001–present 2001 William Knowles / Ryoji Noyori / K. Barry Sharpless 2002 John B. Fenn / Koichi Tanaka / Kurt Wüthrich 2003 Peter Agre / Roderick MacKinnon 2004 Aaron Ciechanover / Avram Hershko / Irwin Rose 2005 Robert H. Grubbs / Richard R. Schrock / Yves Chauvin 2006 Roger D. Kornberg 2007 Gerhard Ertl 2008 Osamu Shimomura / Martin Chalfie / Roger Y. Tsien 2009 Venkatraman Ramakrishnan / Thomas A. Steitz / Ada E. Yonath 2010 Richard F. Heck / Akira Suzuki / Ei-ichi Negishi 2011 Dan Shechtman 2012 Robert Lefkowitz / Brian Kobilka 2013 Martin Karplus / Michael Levitt / Arieh Warshel 2014 Eric Betzig / Stefan Hell / William E. Moerner 2015 Tomas Lindahl / Paul L. Modrich / Aziz Sancar