Michael J. S. Dewar

Michael J. S. Dewar
Born	September 24, 1918(1918-09-24) Ahmednagar, India, Asia
Died	October 10, 1997(1997-10-10) (aged 79) Gainesville, Florida, U.S.
Nationality	American
Institutions	University of London 1951- University of Chicago 1959- University of Texas 1963- University of Florida 1989-1994
Alma mater	University of Oxford
Known for	Dewar-Chatt-Duncanson model
Notable awards	Foreign Member of the Royal Society (1960)[1]; Fellow of the American Academy of Arts and Sciences (1966); Member of the National Academy of Sciences (1983); Honorary Fellow, Balliol College, Oxford (1974); Tilden Medal of the Chemical Society (1954); Harrison Howe Award of the American Chemical Society (1961); Robert Robinson Medal, Chemical Society (1974); G.W. Wheland Medal of the University of Chicago (1976); Evans Award, The Ohio State University (1977); Southwest Regional Award of the American Chemical Society (1978); Davy Medal, Royal Society of London (1982); James Flack Norris Award of the American Chemical Society (1984); William H. Nichols Award of the Americal Chemical Society (1986); Auburn-G. M. Kosolapoff Award of the American Chemical Society (1988); Tetrahedron Prize for Creativity in Organic Chemistry (1989); WATOC Medal (World Association of Theoretical Organic Chemists Meda), (1990).

Michael James Steuart Dewar (born 24 September 1918) was a theoretical chemist born in Ahmednagar, India in 1918.^[2] He received the degrees of Bachelor of Arts, Master of Arts, and DPhil from the Balliol College, Oxford).^[3] He was appointed to the Chair in Chemistry at Queen Mary College of the University of London in 1951.^[3] He moved to the University of Chicago in 1959 and then to the first Robert A. Welch research chair at the University of Texas at Austin in 1963.^[3] After a long and productive period there, he moved to the University of Florida in 1989. He retired in 1994 as Professor Emeritus at the University of Florida.^[2] He died in 1997.^[4][3][5]

Dewar's reputation for providing original solutions to vexing puzzles first developed when he was still a postdoctoral fellow at Oxford University. In 1945, he deduced the correct structure for stipitatic acid, a mold product whose structure had baffled the leading chemists of the day. It involved a new kind of aromatic structure with a seven-membered ring for which Dewar coined the term tropolone.^[6] The discovery of the tropolone structure launched the field of non-benzenoid aromaticity, which witnessed feverish activity for several decades and greatly expanded the chemists' understanding of cyclic π-electron systems. Also in 1945, Dewar devised the then novel notion of a π complex, which he proposed as an intermediate in the benzidine rearrangement.^[7] This offered the first correct rationalization of the electronic structure of complexes of transition metals with alkenes, later known as the Dewar-Chatt-Duncanson model.^[8][9]

Stipitatic Acid

In the early 1950s, Dewar wrote a famous series of six articles^{[10][11][12][13][14][15]} on a general Molecular orbital Theory of Organic Chemistry, which extended and generalised Erich Huckel's original quantum mechanical treatments by using perturbation theory and resonance theory, and which in many ways originated the modern era of theoretical and computational organic chemistry.^[3] Following Woodward and Hoffmann's suggestion of selection rules for pericyclic reactions, Dewar championed (concurrently with Howard Zimmerman) an alternative approach (pioneered by M. G. Evans) to understanding pericyclic reactivity based on aromatic and antiaromatic transition states.^[16] He did not however believe in the utility of Möbius aromaticity, introduced by Edgar Heilbronner in 1964, and now a flourishing area of chemistry.

He is known most famously for the development in the 1970s and 1980s of the Semi-empirical quantum chemistry methods, MINDO, MNDO, AM1 and PM3 that are in the MOPAC computer program, and which for the first time enabled the quantitative study of the structure and mechanism of reaction (transition state) of many real (i.e. large) systems.^[3] This was illustrated in 1974 by computing (using the technique of energy minimisation) the structure of a molecule as large as LSD (with 49 atoms) at a quantum mechanical level (the calculation taking several days of the then state-of-the-art supercomputer time, a CDC 6600). It is worth noting that in 2006, the equivalent calculation takes less than 1 minute on a personal computer. In 2006, the same structure computation can now be completed using high-level ab initio or density functional procedures in less than two days, and semiempirical programs can be used to optimize the structures of molecules with perhaps 10,000 atoms.

He was a member of the International Academy of Quantum Molecular Science.^[4]

References

1. ^ Murrell, J. N. (1998). "Michael James Steuart Dewar. 24 September 1918-11 October 1997". Biographical Memoirs of Fellows of the Royal Society 44: 129. doi:10.1098/rsbm.1998.0009.  edit
2. ^ ^{a b} Michael Dewar IAQMS page
3. ^ ^{a b c d e f} His page from the University of Texas
4. ^ ^{a b} List of IAQMS members
5. ^ Dewar, Michael (1992). A semiempirical life. Columbus, OH: American Chemical Society. ISBN 0-8412-1771-8. 
6. ^ Dewar, M. J. S. (1945). "Structure of Stipitatic Acid". Nature 155 (3924): 50–50. doi:10.1038/155050b0.  edit
7. ^ M. J. S. Dewar (1951). "A review of π Complex Theory". Bull. Soc. Chim. Fr.: C71–79. 
8. ^ Dewar, M. J. S. (1952). "A Molecular Orbital Theory of Organic Chemistry. I. General Principles". Journal of the American Chemical Society 74 (13): 3341. doi:10.1021/ja01133a038.  edit
9. ^ Dewar, M. J. S. (1945). "Mechanism of the Benzidine and Related Rearrangements". Nature 156 (3974): 784–780. doi:10.1038/156784a0.  edit
10. ^ Dewar, M. J. S. (1952). "A Molecular Orbital Theory of Organic Chemistry. I. General Principles". Journal of the American Chemical Society 74 (13): 3341. doi:10.1021/ja01133a038.  edit
11. ^ Dewar, M. J. S. (1952). "A Molecular Orbital Theory of Organic Chemistry. II. The Structure of Mesomeric Systems". Journal of the American Chemical Society 74 (13): 3345. doi:10.1021/ja01133a039.  edit
12. ^ Dewar, M. J. S. (1952). "A Molecular Orbital Theory of Organic Chemistry. III. Charge Displacements and Electromeric Substituents". Journal of the American Chemical Society 74 (13): 3350. doi:10.1021/ja01133a040.  edit
13. ^ Dewar, M. J. S. (1952). "A Molecular Orbital Theory of Organic Chemistry. IV. Free Radicals". Journal of the American Chemical Society 74 (13): 3353. doi:10.1021/ja01133a041.  edit
14. ^ Dewar, M. J. S. (1952). "A Molecular Orbital Theory of Organic Chemistry. V. Theories of Reactivity and the Relationship between Them". Journal of the American Chemical Society 74 (13): 3355. doi:10.1021/ja01133a042.  edit
15. ^ Dewar, M. J. S. (1952). "A Molecular Orbital Theory of Organic Chemistry. VI. Aromatic Substitution and Addition". Journal of the American Chemical Society 74 (13): 3357. doi:10.1021/ja01133a043.  edit
16. ^ M. J. S. Dewar (1971). "Aromatic (Huckel) and Antiaromatic (antiHuckel) Transition states". Angewandte Chemie, Int. Edition 10: 761–776. 

Bibliography

• Josef Michl and Marye Anne Fox (1998). "Michael J. S. Dewar September 24, 1918 — October 10, 1997". Biographical Memoires of the National Academy of Science. http://www.nap.edu/readingroom/books/biomems/mdewar.html. 

Persondata
Name	Dewar
Alternative names
Short description
Date of birth	1918-09-24
Place of birth	Ahmednagar, India
Date of death	1997-10-10
Place of death	Gainesville, Florida, United States