Erich Armand Arthur Joseph Hückel
(August 9, 1896, Berlin – February 16, 1980,
Marburg
Marburg ( or ) is a university town in the German federal state (''Bundesland'') of Hesse, capital of the Marburg-Biedenkopf district (''Landkreis''). The town area spreads along the valley of the river Lahn and has a population of approximat ...
) was a German
physicist
A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe.
Physicists generally are interested in the root or ultimate cau ...
and
physical chemist. He is known for two major contributions:
*The
Debye–Hückel theory
The Debye–Hückel theory was proposed by Peter Debye and Erich Hückel as a theoretical explanation for departures from ideality in solutions of electrolytes and plasmas.
It is a linearized Poisson–Boltzmann model, which assumes an extrem ...
of
electrolytic solution
Solution may refer to:
* Solution (chemistry), a mixture where one substance is dissolved in another
* Solution (equation), in mathematics
** Numerical solution, in numerical analysis, approximate solutions within specified error bounds
* Solutio ...
s
*The
Hückel method of approximate
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 find ...
(MO) calculations on
π electron systems.
Hückel was born in the
Charlottenburg suburb of Berlin. He studied
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
and
mathematics
Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...
from 1914 to 1921 at the
University of Göttingen
The University of Göttingen, officially the Georg August University of Göttingen, (german: Georg-August-Universität Göttingen, known informally as Georgia Augusta) is a public research university in the city of Göttingen, Germany. Founded ...
.
On receiving his
doctorate
A doctorate (from Latin ''docere'', "to teach"), doctor's degree (from Latin ''doctor'', "teacher"), or doctoral degree is an academic degree awarded by universities and some other educational institutions, derived from the ancient formalism ''l ...
, he became an assistant at Göttingen, but soon became an assistant to
Peter Debye
Peter Joseph William Debye (; ; March 24, 1884 – November 2, 1966) was a Dutch-American physicist and physical chemist, and Nobel laureate in Chemistry.
Biography
Early life
Born Petrus Josephus Wilhelmus Debije in Maastricht, Netherland ...
at
Zürich
, neighboring_municipalities = Adliswil, Dübendorf, Fällanden, Kilchberg, Maur, Oberengstringen, Opfikon, Regensdorf, Rümlang, Schlieren, Stallikon, Uitikon, Urdorf, Wallisellen, Zollikon
, twintowns = Kunming, San Francisco
Z ...
. It was there that he and Debye developed their theory (the
Debye–Hückel theory
The Debye–Hückel theory was proposed by Peter Debye and Erich Hückel as a theoretical explanation for departures from ideality in solutions of electrolytes and plasmas.
It is a linearized Poisson–Boltzmann model, which assumes an extrem ...
, in 1923) of electrolytic solutions, elucidating the behavior of strong
electrolyte
An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon ...
s by considering interionic forces, in order to account for their
electrical conductivity
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
and their thermodynamic
activity coefficient
In thermodynamics, an activity coefficient is a factor used to account for deviation of a mixture of chemical substances from ideal behaviour. In an ideal mixture, the microscopic interactions between each pair of chemical species are the same ...
s.
After spending 1928 and 1929 in England and Denmark, working briefly with
Niels Bohr, Hückel joined the faculty of the
Technische Hochschule in
Stuttgart
Stuttgart (; Swabian: ; ) is the capital and largest city of the German state of Baden-Württemberg. It is located on the Neckar river in a fertile valley known as the ''Stuttgarter Kessel'' (Stuttgart Cauldron) and lies an hour from the Sw ...
. In 1935, he moved to
Phillips University in
Marburg
Marburg ( or ) is a university town in the German federal state (''Bundesland'') of Hesse, capital of the Marburg-Biedenkopf district (''Landkreis''). The town area spreads along the valley of the river Lahn and has a population of approximat ...
, where he finally was named Full Professor a year before his retirement 1961. He was a member of the
International Academy of Quantum Molecular Science.
Theories of unsaturated organic molecules
Hückel is most famous for developing the
Hückel method of approximate
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 find ...
(MO) calculations on
π electron systems, a simplified
quantum-mechanical
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, qu ...
method to deal with planar unsaturated
organic
Organic may refer to:
* Organic, of or relating to an organism, a living entity
* Organic, of or relating to an anatomical organ
Chemistry
* Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...
molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and b ...
s. In 1930 he proposed a
σ/π separation theory to explain the restricted rotation of
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, a ...
(compounds containing a C=C
double bond). This model extended a 1929 interpretation of the bonding in
triplet oxygen by
Lennard-Jones
Sir John Edward Lennard-Jones (27 October 1894 – 1 November 1954) was a British mathematician and professor of theoretical physics at the University of Bristol, and then of theoretical science at the University of Cambridge. He was an ...
. According to Hückel, only the ethene σ bond is axially symmetric about the C-C axis, but the π bond is not; this restricts rotation. In 1931 he generalized his analysis by formulating both
valence bond (VB) and
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 find ...
(MO) descriptions of
benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
and other cycloconjugated hydrocarbons. Although undeniably a cornerstone of organic chemistry, Hückel's concepts were undeservedly unrecognized for two decades. His lack of communication skills contributed. The famous Hückel
4n+2 rule for determining whether ring molecules composed of C=C bonds would show
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 ...
properties was first stated clearly by
Doering in a 1951 article on
tropolone. Tropolone had been recognised as an
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 ...
molecule by
Dewar in 1945.
In 1936, Hückel developed the theory of π-conjugated
biradicals (non-Kekulé molecules). The first example, known as the
Schlenk-Brauns hydrocarbon, had been discovered in the same year. The credit for explaining such biradicals is usually given to
Christopher Longuet-Higgins
Hugh Christopher Longuet-Higgins (April 11, 1923 – March 27, 2004) was a British scholar and teacher. He was the Professor of Theoretical Chemistry at the University of Cambridge for 13 years until 1967 when he moved to the University of Edin ...
in 1950.
In 1937 Hückel refined his MO theory of
pi electrons in unsaturated organic molecules. This is still used occasionally as an approximation, though the more precise PPP
Pariser–Parr–Pople method
In molecular physics, the Pariser–Parr–Pople method applies semi-empirical quantum mechanical methods to the quantitative prediction of electronic structures and spectra, in molecules of interest in the field of organic chemistry. Previous meth ...
succeeded it in 1953. "Extended Hückel MO theory" (
EHT) applies to both
sigma and pi electrons, and has its origins in work by
William Lipscomb and
Roald Hoffmann for nonplanar molecules in 1962.
Poem about Schrödinger
According to
Felix Bloch, Erich Hückel "incited and helped" the students at the University of Zurich to write poems about their great professors.
The poem about
Erwin Schrödinger went like this:
Gar Manches rechnet Erwin schon
Mit seiner Wellenfunktion.
Nur wissen möcht' man gerne wohl
Was man sich dabei vorstell'n soll.
It was freely translated by
Felix Bloch:
Erwin with his psi can do
Calculations quite a few.
But one thing has not been seen:
Just what does psi really mean?
Awards
*1965
Otto Hahn Prize for Chemistry and Physics
References
Further reading
*
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*
*
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* E. Hückel, ''Ein Gelehrtenleben: Ernst u. Satire'' (1975 ).
* A. Karachalios, ''Erich Hückel (1896 –1980): From Physics to Quantum Chemistry'' (Springer, 2010 ).
{{DEFAULTSORT:Huckel, Erich
1896 births
1980 deaths
20th-century German physicists
German physical chemists
Members of the International Academy of Quantum Molecular Science
Foreign Members of the Royal Society
Theoretical chemists
Scientists from Berlin