Michael James Steuart Dewar (24 September 1918 – 10 October 1997) was an American

theoretical chemist Theoretical chemistry is the branch of chemistry which develops theoretical generalizations that are part of the theoretical arsenal of modern chemistry: for example, the concepts of chemical bonding, chemical reaction, valence, the surface ...

.Michael Dewar IAQMS page
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Education and early life

Dewar was the son of Scottish parents, Annie Balfour (Keith) and Francis Dewar. He received the degrees of Bachelor of Arts, Master of Arts, and

DPhil A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is ...

from Balliol College, Oxford.

Career and research

Dewar was appointed to the Chair in Chemistry at

Queen Mary College , mottoeng = With united powers , established = 1785 – The London Hospital Medical College1843 – St Bartholomew's Hospital Medical College1882 – Westfield College1887 – East London College/Queen Mary College , type = Public researc ...

of the

University of London The University of London (UoL; abbreviated as Lond or more rarely Londin in post-nominals) is a federal public research university located in London, England, United Kingdom. The university was established by royal charter in 1836 as a degree ...

in 1951. He moved to the

University of Chicago The University of Chicago (UChicago, Chicago, U of C, or UChi) is a private university, private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park, Chicago, Hyde Park neighborhood. The University of Chic ...

in 1959 and then to the first Robert A. Welch research chair at the

University of Texas at Austin The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,07 ...

in 1963. After a long and productive period there, he moved to the

University of Florida The University of Florida (Florida or UF) is a public land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...

in 1989. He retired in 1994 as Professor Emeritus at the University of Florida. He died in 1997.List of IAQMS members
/ref> Dewar's reputation for providing original solutions to vexing puzzles first developed when he was still a postdoctoral fellow at the

University of Oxford , mottoeng = The Lord is my light , established = , endowment = £6.1 billion (including colleges) (2019) , budget = £2.145 billion (2019–20) , chancellor ...

. In 1945, he deduced the correct structure for stipitatic acid, a mould product whose structure had baffled the leading chemists of the day. It involved a new kind of

aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

structure with a seven-membered ring for which Dewar coined the term ''

tropolone Tropolone is an organic compound with the chemical formula . It is a pale yellow solid that is soluble in organic solvents. The compound has been of interest to research chemists because of its unusual electronic structure and its role as a ligan ...

''. The discovery of the tropolone structure launched the field of non-benzenoid

aromaticity In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

, 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. This offered the first correct rationalisation of the electronic structure of complexes of

transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that ca ...

s with

alkenes In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

, later known as the

Dewar–Chatt–Duncanson model The Dewar–Chatt–Duncanson model is a model in organometallic chemistry that explains the chemical bonding in transition metal alkene complexes. The model is named after Michael J. S. Dewar, Joseph Chatt and L. A. Duncanson. The alkene donat ...

. In the early 1950s, Dewar wrote a famous series of six articles on a general

Molecular orbital In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of findin ...

Theory of Organic Chemistry, which extended and generalised Erich Hückel's original quantum mechanical treatments by using

perturbation theory In mathematics and applied mathematics, perturbation theory comprises methods for finding an approximate solution to a problem, by starting from the exact solution of a related, simpler problem. A critical feature of the technique is a middl ...

and resonance theory, and which in many ways originated the modern era of theoretical and computational organic chemistry. Following Woodward and

Hoffmann Hoffmann is a German language, German surname. People A *Albert Hoffmann (horticulturist), Albert Hoffmann (1846–1924), German horticulturist *Alexander Hoffmann (politician), Alexander Hoffmann (born 1975), German politician *Arthur Hoffmann ...

's suggestion of

selection rules In physics and chemistry, a selection rule, or transition rule, formally constrains the possible transitions of a system from one quantum state to another. Selection rules have been derived for electromagnetic transitions in molecules, in atoms, i ...

for

pericyclic In organic chemistry, a pericyclic reaction is the type of organic reaction wherein the transition state of the molecule has a cyclic geometry, the reaction progresses in a concerted fashion, and the bond orbitals involved in the reaction overlap ...

reactions, Dewar championed (concurrently with Howard Zimmerman) an alternative approach (which he erroneously felt had been pioneered by M. G. Evans) to understanding pericyclic reactivity based on

and

antiaromatic Antiaromaticity is a chemical property of a cyclic molecule with a π electron system that has higher energy, i.e., it is less stable due to the presence of 4n delocalised (π or lone pair) electrons in it, as opposed to aromaticity. Unlike aroma ...

transition states. 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, Austin Model 1, AM1 and PM3 (chemistry), 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. This was illustrated in 1974 by computing (using the technique of energy BFGS method, 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 Control Data, 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 quantum chemistry methods, ab initio or Density-functional theory, density functional procedures in less than two days, and semiempirical programs can be used to optimise the structures of molecules with perhaps 10,000 atoms. He was a member of the International Academy of Quantum Molecular Science.

Awards and honours

His accolades include: 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 (1982); James Flack Norris Award of the American Chemical Society (1984); William H. Nichols Award of the American Chemical Society (1986); Auburn-G. M. Kosolapoff Award of the American Chemical Society (1988); Tetrahedron Prize, Tetrahedron Prize for Creativity in Organic Chemistry (1989); WATOC Medal (World Association of Theoretical Organic Chemists Meda), (1990).

Personal life

He is the father of Robert Dewar and C.E. Steuart Dewar.''DEWAR'' https://www.cesdewar.com/

References

{{DEFAULTSORT:Dewar, Michael James Steuart 1918 births 1997 deaths University of Florida faculty Fellows of the Royal Society British chemists Alumni of Balliol College, Oxford Academics of Queen Mary University of London Members of the International Academy of Quantum Molecular Science Theoretical chemists Computational chemists