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 o ...

.Michael Dewar IAQMS page
/ref>

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, DPhil; or ) is a terminal degree that usually denotes the highest level of academic achievement in a given discipline and is awarded following a course of graduate study and original research. The name of the deg ...

from

Balliol College, Oxford Balliol College () is a constituent college of the University of Oxford. Founded in 1263 by nobleman John I de Balliol, it has a claim to be the oldest college in Oxford and the English-speaking world. With a governing body of a master and aro ...

Career and research

Dewar was appointed to the Chair in Chemistry at

Queen Mary College Queen Mary University of London (QMUL, or informally QM, and formerly Queen Mary and Westfield College) is a public research university in Mile End, East London, England. It is a member institution of the federal University of London. Today, ...

of the

University of London The University of London (UoL; abbreviated as Lond or more rarely Londin in Post-nominal letters, post-nominals) is a collegiate university, federal Public university, public research university located in London, England, United Kingdom. The ...

in 1951. He moved to the

University of Chicago The University of Chicago (UChicago, Chicago, or UChi) is a Private university, private research university in Chicago, Illinois, United States. Its main campus is in the Hyde Park, Chicago, Hyde Park neighborhood on Chicago's South Side, 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 university, public research university in Austin, Texas, United States. Founded in 1883, it is the flagship institution of the University of Texas System. With 53,082 stud ...

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 university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...

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 The University of Oxford is a collegiate university, collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the List of oldest un ...

. 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 organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

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 liga ...

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

aromaticity In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugation alone. The e ...

, 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 Benzidine (trivial name), also called 1,1'-biphenyl-4,4'-diamine (systematic name), is an organic compound with the chemical formula, formula (C6H4NH2)2. It is an aromatic amine. It is a component of a test for cyanide. Related derivatives are ...

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. The lanthanide and actinid ...

s with

alkenes In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

, 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 don ...

. 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 finding ...

Theory of Organic Chemistry, which extended and generalised

Erich Hückel Erich Armand Arthur Joseph Hückel (August 9, 1896, Berlin – February 16, 1980, Marburg) was a German physicist and physical chemist. He is mainly known for the Debye–Hückel theory of electrolytic solutions and the Hückel method of approx ...

'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 middle ...

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 *Adolph Hoffmann (1858–1930), German politician *Albert Hoffmann (horticulturist), Albert Hoffmann (1846–1924), German horticulturist *Alexander Hoffmann (politician), Alexander Hoffma ...

'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, in ...

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 overl ...

reactions, Dewar championed (concurrently with

Howard Zimmerman Howard E. Zimmerman (July 5, 1926 – February 12, 2012) was a professor of chemistry at the University of Wisconsin–Madison. He was elected to the National Academy of Sciences in 1980 and the recipient of the 1986 American Institute of Chemis ...

) 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 state In chemistry, the transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. It is often marked w ...

s. He did not however believe in the utility of

Möbius aromaticity In organic chemistry, Möbius aromaticity is a special type of aromaticity believed to exist in a number of organic molecules. In terms of molecular orbital theory these compounds have in common a monocyclic array of molecular orbitals in which t ...

, introduced by

Edgar Heilbronner Edgar Heilbronner (13 May 1921 – 28 August 2006) was a Switzerland, Swiss Germany, German chemist. In 1964 he published the concept of Möbius–Hückel concept, Möbius cyclic annulenes, but the first Möbius aromatic was not synthesize ...

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 Semi-empirical quantum chemistry methods are based on the Hartree–Fock formalism, but make many approximations and obtain some parameters from empirical data. They are very important in computational chemistry for treating large molecules where t ...

MINDO MINDO, or Modified Intermediate Neglect of Differential Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Intermediate Neglect of Differential Overlap ...

MNDO MNDO, or Modified Neglect of Diatomic Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Neglect of Diatomic Differential Overlap integral approximation. ...

, AM1 and PM3 that are in the

MOPAC MOPAC is a computational chemistry software package that implements a variety of semi-empirical quantum chemistry methods based on the neglect of diatomic differential overlap (NDDO) approximation and fit primarily for gas-phase thermochemistry ...

computer program, and which for the first time enabled the quantitative study of the structure and mechanism of reaction (

) of many ''real'' (i.e. large) systems. This was illustrated in 1974 by computing (using the technique of energy minimisation) the structure of a molecule as large as

LSD Lysergic acid diethylamide, commonly known as LSD (from German ; often referred to as acid or lucy), is a semisynthetic, hallucinogenic compound derived from ergot, known for its powerful psychological effects and serotonergic activity. I ...

(with 49 atoms) at a quantum mechanical level (the calculation taking several days of the then state-of-the-art

supercomputer A supercomputer is a type of computer with a high level of performance as compared to a general-purpose computer. The performance of a supercomputer is commonly measured in floating-point operations per second (FLOPS) instead of million instruc ...

time, a

CDC 6600 The CDC 6600 was the flagship of the 6000 series of mainframe computer systems manufactured by Control Data Corporation. Generally considered to be the first successful supercomputer, it outperformed the industry's prior recordholder, the I ...

). 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 ( ) is a Latin term meaning "from the beginning" and is derived from the Latin ("from") + , ablative singular of ("beginning"). Etymology , from Latin, literally "from the beginning", from ablative case of "entrance", "beginning", related t ...

or 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 The International Academy of Quantum Molecular Science (IAQMS) is an international scientific learned society covering all applications of quantum theory to chemistry and chemical physics. It was created in Menton in 1967. The founding members we ...

Awards and honours

His accolades include: Fellow of the

American Academy of Arts and Sciences The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...

(1966); Member of the

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...

(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 The Davy Medal is awarded by the Royal Society of London "for an outstandingly important recent discovery in any branch of chemistry". Named after Humphry Davy, the medal is awarded with a monetary gift, initially of £1000 (currently £2000). Re ...

(1982); James Flack Norris Award of the American Chemical Society (1984); William H. Nichols Award of the

American Chemical Society The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 155,000 members at all ...

(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 Medal), (1990).

Personal life

He is the father of

Robert Dewar Robert Berriedale Keith Dewar (21 June 1945 – 30 June 2015) was an American computer scientist and educator. He helped to develop programming languages and compilers and was an outspoken advocate of freely licensed open-source software. He was ...

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 American theoretical chemists American computational chemists