The Nobel Prize in Chemistry:
The Development of Modern Chemistry
by Bo
G. Malmström
First published December 1999
1. Introduction
1.1. Chemistry at the Borders to Physics and Biology
The turn of the century 1900 was also a turning
point in the history of chemistry. Consequently, a survey of the
Nobel Prizes in Chemistry during this century will provide an analysis
of important trends in the development of this branch of the Natural
Sciences, and this is the aim of the present essay. Chemistry has
a position in the center of the sciences, bordering onto physics,
which provides its theoretical foundation, on one side, and onto
biology on the other, living organisms being the most complex of
all chemical systems. Thus, the fact that chemistry flourished during
the beginning of the 20th century is intimately connected with fundamental
developments in physics.
In 1897 Sir
Joseph John Thomson (1856-1940) of Cambridge announced his discovery
of the electron, for which he was awarded the Nobel Prize for Physics
in 1906. He found that these negatively charged 'corpuscles', as
he called them, have a mass 1000 times smaller than the hydrogen
atom. Thomson's discovery had, of course, important implications
for chemistry, as it showed that the atom is not an indivisible
building block of chemical compounds, but it took a number of years
before this led to developments of direct relevance to chemistry.
In 1911 Ernest Rutherford (1871-1937),
who had worked in Thomson's laboratory in the 1890s, formulated
an atomic model, according to which the positively charged atomic
nucleus carries most of the mass of the atom but occupies a very
small part of its volume. This is instead created by a cloud of
electrons circling around the nucleus. Rutherford received the Nobel
Prize for Chemistry already in 1908 for his work on radioactivity
(see Section 2).
It was soon realized that in Rutherford's atomic
model the stability of atoms was at variance with the laws of classical
physics, since the electrons would lose energy in the form of electromagnetic
radiation and eventually fall into the nucleus. Niels
Bohr (1885-1962) from Copenhagen understood that an important
clue to the solution of this problem could be found in the distinct
lines observed in the spectra of atoms, the regularities of which
had been discovered in 1890 by the physics professor Johannes (Janne)
Rydberg (1854-1919) at Lund University. Consequently, Bohr formulated
in 1913 an alternative atomic model, in which only certain circular
orbits of the electrons are allowed. In this model light is emitted
(or absorbed), when an electron makes a transition from one orbit
to another. Bohr received the Nobel Prize for Physics in 1922 for
his work on the structure of atoms.
Another step in the application of the electronic
structure of atoms to chemistry was taken in 1916, when Gilbert
Newton Lewis (1875-1946) suggested that strong (covalent) bonds
between atoms involve a sharing of two electrons between these atoms
(electron-pair bond). Lewis also contributed fundamental work in
chemical thermodynamics, and his brilliant textbook, Thermodynamics
(1923), written together with Merle Randall (1880-1950), is counted
as one of the masterworks in the chemical literature. Much to the
surprise of the chemical community, Lewis never received a Nobel
Prize.
Even if the contributions just described were
made a decade or more after Thomson's discovery, much important
work in the borderland between physics and chemistry was published
in the 1890s, and this was naturally given a strong consideration
by the first Nobel Committee for Chemistry (see Section 2). In fact,
three of the Laureates during the first decade, Jacobus Henricus van't Hoff (1852-1911),
Svante Arrhenius (1859-1927) and Wilhelm Ostwald (1853-1932), are
generally regarded as the founders of a new branch of chemistry,
physical chemistry. Fundamental work had, however, also been done
in more traditional chemical fields, particularly in organic chemistry
and in the chemistry of natural products, which is clearly reflected
in the early prizes. The Nobel Committee, in addition, showed great
openness and foresight by recognizing the other border, that towards
biology, already in 1907 with the prize to Eduard Buchner (1860-1917) "for
his biochemical researches and his discovery of cell-free fermentation".
1.2. The Mechanics of the Work in the Nobel Committee for Chemistry
According to the statutes
of the Nobel Foundation, the Nobel Committees should have five members,
but the Committee for Chemistry has in recent decades chosen to
widen its expertise by adding a number of adjunct members (five
in 1998) with the same voting rights as the regular members. Until
recently there was no limit other than age on how many times regular
members could be re-elected for 3-year terms, so that some members
sat on the Committee for a very long period. For example, Professor
Arne Westgren (1889-1975) of Stockholm, who was secretary of the
Nobel Committees for Physics and for Chemistry 1926-1943, was also
Chairman of the Committee for Chemistry 1944-1965. Present rules,
however, only allow two re-elections, so that a member's maximum
total time on the Committee will be nine years.
Only persons that have been properly nominated
before 31 January can be considered for the Nobel Prize in a given
year. Consequently, the Nobel Committee starts its work by sending
out invitations to nominate in the autumn of the preceding year.
Recipients of these invitations, for both Physics and Chemistry,
are: 1) Swedish and foreign members of the Royal Swedish Academy
of Sciences; 2) members of the Nobel Committees for Physics and
for Chemistry; 3) Nobel Laureates in Physics and Chemistry; 4) professors
in Physics and Chemistry in Scandinavian universities and at the
Karolinska Institute; 5) professors in these subjects in a number
of universities outside Scandinavia, selected on a rotation basis
by the Academy of Sciences; and 6) other scientists that the Academy
chooses to invite.
In the initial years of the Nobel Prize, about
300 invitations to nominate for the Nobel Prize for Chemistry were
sent out, but this number has increased over the years and was as
high as 2,650 in 1998. The number of nominations received has also
increased dramatically from 20-40 during the first decade to 400-500
in the 1990s. The number of candidates is usually smaller than the
number of nominations, since many candidates receive more than one
nomination. During the first few years only about 10 scientists
were nominated, but in recent years this number has been in the
range of 250-350.
The invitations to nominate are personal, and
it is stressed that nominations should not be discussed with the
candidate or with colleagues. This is unfortunately not always respected
as is obvious from the fact that many identically worded nominations
are some years received from the same university. For this reason
the Committee does not put much weight on the number of nominations
a given candidate receives, unless clearly independent nominations
come from different universities in different countries. This attitude
was not taken in earlier years however, as is evident from the following
statement made by Committee Chairman Arne Westgren, in a survey
over the first 60 years of the Nobel Prize for Chemistry [1]: "In
fact, if a scientist is proposed by a large number of sponsors in
the preliminary international voting, he is normally selected by
the Academy."
Often the same candidate receives nominations
both for chemistry and for physics or for chemistry and for medicine.
This problem was met already in 1903, when Arrhenius had been nominated
both for the Prize for Chemistry and that for Physics, and in its
deliberations the Committee for Chemistry suggested that he should
be awarded half of each Prize, but this idea was rejected by the
Committee for Physics. Because of such borderline problems, the
Committee for Chemistry nowadays has joint meetings with those for
Physics and for Physiology or Medicine. However, as pronounced by
Westgren [1]: "It is now generally recognized that the important
thing is to decide whether work which can with equal justice be
reckoned as chemistry and physics or chemistry and medicine, is
in fact worthy of a Nobel Prize." For example, Peter
Mitchell (1920-1992), who received the 1978 Nobel Prize for
Chemistry, could with equal justice have been awarded the Prize
for Physiology or Medicine.
Nobel's
will laid down that the prize should be awarded for work done
during the preceding year, but in the statutes governing the committee
work this has been interpreted to mean the most recent results,
or for older work provided its significance has only recently been
demonstrated. It was undoubtedly this rule that excluded Stanislao
Cannizzaro (1826-1910) from receiving one of the first Nobel Prizes,
since his work on drawing up a reliable table of atomic weights,
helping to establish the periodic system, was done in the middle
of the 19th century. A more recent example is Henry Eyring (1901-1982),
whose brilliant theory for the rates of chemical reactions, published
in 1935, was apparently not understood by members of the Nobel Committee
until much later. As a compensation the Royal Swedish Academy of
Sciences gave him, in 1977, its highest honor, other than the Nobel
Prize, the Berzelius Medal in gold.
2. The First Decade of Nobel Prizes for Chemistry
So much fundamental work in chemistry had been
carried out during the last two decades of the 19th century that,
as stated by Westgren [1], "During the first few years the
Academy was chiefly faced with merely deciding the order in which
these scientists should be awarded the prize." For the first
prize in 1901 the Academy had to consider 20 nominations, but no
less than 11 of these named van't Hoff, who was also chosen by the
Committee for Chemistry. van't Hoff had already during his thesis
work in Utrecht in 1874 published his suggestion that the carbon
atom has its four valences directed towards the corners of a regular
tetrahedron, a concept which is the very foundation of modern organic
chemistry. The Nobel Prize was, however, awarded for his later work
on chemical kinetics and equilibria and on the osmotic pressure
in solution, published in 1884 and 1886, when he held a professorship
in Amsterdam. When he received the prize he had, however, left this
for a position at Akademie der Wissenschaften in Berlin in 1896.
In his 1886 work van't Hoff showed that most
dissolved chemical compounds give an osmotic pressure equal to the
gas pressure they would have exerted in the absence of the solvent.
An apparent exception was aqueous solutions of electrolytes (acids,
bases and their salts), but in the following year Arrhenius showed
that this anomaly could be explained, if it is assumed that electrolytes
in water dissociate into ions. The rudiments of his dissociation
theory Arrhenius had already presented in his doctoral thesis, which
was defended in Uppsala in 1884 and was not entirely well received
by the faculty. It was, however, strongly supported by Ostwald in
Riga, who, in fact, travelled to Uppsala to initiate a collaboration
with Arrhenius. In 1886-90 Arrhenius did work with Ostwald, first
in Riga and then in Leipzig, and also with van't Hoff in Berlin.
When Arrhenius was awarded the Nobel Prize for Chemistry in 1903,
he was since 1895 professor of physics in Stockholm, and he was
also nominated for the Prize for Physics (see Section 1).
The award of the Nobel Prize for Chemistry in
1909 to Ostwald was chiefly in recognition of his work on catalysis
and the rates of chemical reactions. Ostwald had in his investigations,
following up observations in his thesis in 1878, shown that the
rate of acid-catalyzed reactions is proportional to the square of
the strength of the acid, as measured by titration with base. His
work offered support not only to Arrhenius' theory of dissociation
but also to van't Hoff's theory for osmotic pressure. Ostwald was
founder and editor of Zeitschrift für physikalische Chemie,
the publication of which is generally regarded as the birth of this
new branch of chemistry.
Three of the Nobel Prizes for Chemistry during
the first decade were awarded for pioneering work in organic chemistry.
In 1902 Emil Fischer (1852-1919), then
in Berlin, was given the prize for "his work on sugar and purine
syntheses". Fischer's work is an example of the growing interest
from organic chemists in biologically important substances, thus
laying the foundation for the development of biochemistry, and at
the time of the award Fischer mainly devoted himself to the study
of proteins. Another major influence from organic chemistry was
the development of chemical industry, and a chief contributor here
was Fischer's teacher, Adolf von Baeyer (1835-1917) in
Munich, who was awarded the prize in 1905 "in recognition of
his services in the advancement of organic chemistry and the chemical
industry,...". His contributions include, in particular, structure
determination of organic dyes (indigo, eosin) and the study of aromatic
compounds (terpenes). The third Laureate working in organic chemistry
was Otto Wallach (1847-1931) in Göttingen,
who, like von Baeyer, contributed to alicyclic chemistry, studying
not only terpenes but also camphor and other components of ethereal
oils. At the award ceremony in 1910 the importance of his discoveries
for chemical industry was emphasized.
Two of the early prizes were given for the discovery
of new chemical elements. Sir
William Ramsay (1852-1916) from London received the 1904 Nobel
Prize for Chemistry for his discovery of a number of noble gases,
a new group of chemically unreactive elements. The first one isolated
was argon ("the inactive one"), which Ramsay discovered
in 1894, in collaboration with Lord Rayleigh [John William Strutt
Rayleigh (1842-1919)] of the Royal Institution, who was awarded
the Prize for Physics in the same year, his investigations of the
density of air and other gases forming the basis for this discovery.
The following year Ramsay found helium, earlier observed only in
the solar spectrum (hence its name), in emanations from radium,
thus anticipating later prizes for nuclear chemistry (see below).
Later (1898) he also discovered, by fractional distillation of liquid
air, neon ("the new one"), krypton ("the hidden one")
and xenon ("the strange one"). The isolation of another
element, fluorine, by Henri Moissan (1852-1907) in Paris
was honored with the 1906 Nobel Prize. In attempts to prepare artificial
diamonds Moissan had also developed an electric furnace, and this
was specifically mentioned in the prize citation, perhaps a reflection
of the stipulation in Nobel's will that the Prize for Chemistry
can be given "for the most important discovery or improvement".
Ernest Rutherford [Lord Rutherford since 1931],
professor of physics in Manchester, was awarded the Nobel Prize
for Chemistry in 1908 for his investigations of the chemistry of
radioactive substances. The discovery of radioactivity had already
been recognized with the Nobel Prize for Physics in 1903, but what
Rutherford established was the transformation of one element into
another, earlier the alchemist's dream. In his studies of uranium
disintegration he found two types of radiation, named a- and b-rays,
and by their deviation in electric and magnetic fields he could
show that a-rays consist of positively charged particles. His demonstration
that these particles are helium nuclei came in the same year as
he received the Nobel Prize. Even if the importance of Rutherford's
work for chemistry is obvious, he naturally had also received many
nominations for the Nobel Prize for Physics (see Section 1).
In 1897 Eduard Buchner, at the time professor
in Tübingen, published results demonstrating that the fermentation
of sugar to alcohol and carbon dioxide can take place in the absence
of yeast cells. Earlier it had generally been considered that living
cells possess a "vital force", which makes the life processes
possible, even if a few prominent chemists, foremost Jöns Jacob
Berzelius (1779-1848) and Justus von Liebig (1803-73), had advocated
a chemical basis for life. The vitalistic outlook had been fiercely
defended by Louis Pasteur (1822-1895), who maintained that alcoholic
fermentation can only occur in the presence of living yeast cells.
Buchner's experiments showed unequivocally that fermentation is
a catalytic process caused by the action of enzymes, as had been
suggested by Berzelius for all life processes, and Buchner called
his extract zymase ("enzymes in yeast"). Because of Buchner's
experiment, 1897 is generally regarded as the birth date for biochemistry
proper. Buchner was awarded the Nobel Prize for Chemistry in 1907,
when he was professor at the agricultural college in Berlin. This
confirmed the prediction of his former teacher, Adolf von Baeyer:
"This will make him famous, in spite of the fact that he lacks
talent as a chemist."
3. The Nobel Prizes for Chemistry 1911-2000
A survey of the Nobel Prizes for Chemistry awarded
during the 20th century, reveals that the development of this field
includes breakthroughs in all of its branches, with a certain dominance
for progress in physical chemistry and its subcategories (chemical
thermodynamics and chemical change), in chemical structure, in several
areas of organic chemistry as well as in biochemistry. Of course,
the borders between different areas are diffuse, so many Laureates
will be mentioned in more than one place.
3.1. General and Physical Chemistry
The Nobel Prize for Chemistry in 1914 was awarded
to Theodore William Richards (1868-1928)
of Harvard University for "his accurate determinations of the
atomic weight of a large number of chemical elements". Most
atomic weights in Cannizzaros table (see Section 1.2) had already
been determined in the 19th century, particularly by the Belgian
chemist Jean Servais Stas (1813-91), but Richards showed that many
of them were in error, mainly because Stas had worked with very
concentrated solutions, leading to co-precipitation. In 1913 Richards
had discovered that the atomic weight of natural lead and of that
formed in radioactive decay of uranium minerals differ. This pointed
to the existence of isotopes, i.e., atoms of the same element with
different atomic weights, which was accurately demonstrated by Francis William Aston (1877-1945)
at Cambridge University, with the aid of an instrument developed
by him, the mass spectrograph. Aston also showed that the atomic
weights of pure isotopes are integral numbers, with the exception
of hydrogen, the atomic weight of which is 1.008. For his achievements
Aston received the Nobel Prize for Chemistry in 1922.
One branch of physical chemistry deals with
chemical events at the interface of two phases, for example, solid
and liquid, and phenomena at such interfaces have important applications
all the way from technical to physiological processes. Detailed
studies of adsorption on surfaces, were carried out by Irving Langmuir (1881-1957) at
the research laboratory of General Electric Company, and when he
was awarded the Nobel Prize for Chemistry in 1932, he was the first
industrial scientist to receive this distinction.
Two of the Prizes for Chemistry in more recent
decades have been given for fundamental work in the application
of spectroscopic methods to chemical problems. Spectroscopy had
already been recognized with Prizes for Physics in 1952, 1955 and
1961, when Gerhard
Herzberg (1904-1999), a physicist at the University of Saskatchewan,
received the Nobel Prize for Chemistry in 1971 for his molecular
spectroscopy studies "of the electronic structure and geometry
of molecules, particularly free radicals". The most used spectroscopic
method in chemistry is undoubtedly NMR (nuclear magnetic resonance),
and Richard R. Ernst
(1933- ) at ETH in Zürich was given the Nobel Prize for Chemistry
in 1991 for "the development of the methodology of high resolution
nuclear magnetic resonance (NMR) spectroscopy". Ernst's methodology
has now made it possible to determine the structure in solution
(in contrast to crystals; cf. Section 3.5) of large molecules, such
as proteins.
3.2. Chemical Thermodynamics
The first Nobel Prize for Chemistry, that to
van't Hoff, was in part for work in chemical thermodynamics, and
many later contributions in this area have also been recognized
with Nobel Prizes. Already in 1920 Walther Hermann Nernst (1864-1941)
of Berlin received this award for work in thermochemistry, despite
a 16-year opposition to this recognition from Arrhenius [2]. Nernst
had shown that it is possible to determine the equilibrium constant
for a chemical reaction from thermal data, and in so doing he formulated
what he himself called the third law of thermodynamics. This states
that the entropy, a thermodynamic quantity, which is a measure of
the disorder in the system, approaches zero as the temperature goes
towards absolute zero. van't Hoff had derived the mass action equation
in 1886, with the aid of the second law which says, that the entropy
increases in all spontaneous processes [this had already been done
in 1876 by J. Willard Gibbs (1839-1903) at Yale, who certainly had
deserved a Nobel Prize, but his work had been published in an obscure
place]. According to the second law, heat of reaction is not an
accurate measure of chemical equilibrium, as had been assumed by
earlier investigators. But Nernst showed in 1906 that it is possible
with the aid of the third law, to derive the necessary parameters
from the temperature dependence of thermochemical quantities.
To prove his heat theorem (the third law) Nernst
carried out thermochemical measurements at very low temperatures,
and such studies were extended in the 1920s by G.N. Lewis (see Section
1.1) in Berkeley. Lewis's new formulation of the third law was confirmed
by his student William Francis Giauque (1895-1982),
who extended the temperature range experimentally accessible by
introducing the method of adiabatic demagnetization in 1933. With
this he managed to reach temperatures a few thousandths of a degree
above absolute zero and could thereby provide extremely accurate
entropy estimates. He also showed that it is possible to determine
entropies from spectroscopic data. Giauque was awarded the Nobel
Prize for Chemistry in 1949 for his contributions to chemical thermodynamics.
The next Nobel Prize given for work in thermodynamics
went to Lars Onsager (1903-1976) of Yale
University in 1968 for contributions to the thermodynamics of irreversible
processes. Classical thermodynamics deals with systems at equilibrium,
in which the chemical reactions are said to be reversible, but many
chemical systems, for example, the most complex of all, living organisms,
are far from equilibrium and their reactions are said to be irreversible.
With the aid of statistical mechanics Onsager developed in 1931
his so-called reciprocal relations, describing the flow of matter
and energy in such systems, but the importance of his work was not
recognized until the end of the 1940s. A further step forward in
the development of non-equilibrium thermodynamics was taken by Ilya
Prigogine (1917- ) in Bruxelles, whose theory of dissipative
structures was awarded with the Nobel Prize for Chemistry in 1977.
3.3. Chemical Change
The chief method to get information about the
mechanism of chemical reactions is chemical kinetics, i.e., measurements
of the rate of the reaction as a function of reactant concentrations
as well as its dependence on temperature, pressure and reaction
medium. Important work in this area had been done already in the
1880s by two of the early Laureates, van't Hoff and Arrhenius, who
showed that it is not enough for molecules to collide for a reaction
to take place. Only molecules with sufficient kinetic energy in
the collision do, in fact, react, and Arrhenius derived an equation
in 1889 allowing the calculation of this activation energy from
the temperature dependence of the reaction rate. With the advent
of quantum mechanics in the 1920s (see Section 3.4), Eyring developed
his transition-state theory in 1935 and this showed that the activation
entropy is also important. Strangely, Eyring never received a Nobel
Prize (see Section 1.2).
In 1956 Sir
Cyril Norman Hinshelwood (1897-1967) of Oxford and Nikolay Nikolaevich Semenov (1896-1986)
from Moscow shared the Nobel Prize for Chemistry "for their
researches into the mechanism of chemical reactions". Among
Hinshelwood's major contributions can be mentioned his detailed
elucidation of the mechanism for the reaction between oxygen and
hydrogen, whereas Semenov's award was for his studies of so-called
chain reactions.
A limit in investigating reaction rates is set
by the speed with which the reaction can be initiated. If this is
done by rapid mixing of the reactants, the time limit is about one
thousandth of a second (millisecond). In the 1950s Manfred Eigen (1927- ) from Göttingen
developed chemical relaxation methods that allow measurements in
times as short as a thousandth or a millionth of a millisecond (microseconds
or nanoseconds). The methods involve disturbing an equilibrium by
rapid changes in temperature or pressure and then follow the passage
to a new equilibrium. Another way to initiate some reactions rapidly
is flash photolysis, i.e., by short light flashes, a method developed
by Ronald G.W. Norrish (1897-1978)
at Cambridge and George Porter (Lord Porter since
1990) (1920- ) in London. Eigen received one half and Norrish and
Porter shared the other half of the Nobel Prize for Chemistry in
1967. Henry
Taube (1915- ) of Stanford University was awarded the Nobel
Prize for Chemistry in 1983 "for his work on the mechanism
of electron transfer reactions, especially in metal complexes".
Even if Taube's work was on inorganic reactions, electron transfer
is important in many catalytic processes used in industry and also
in biological systems, for example, in respiration and photosynthesis.
The latest prize for work in chemical kinetics was that to Dudley R. Herschbach (1932- )
at Harvard University, Yuan T. Lee (1936- ) of Berkeley
and John C. Polanyi (1929- ) from
Toronto in 1986. Herschbach and his student Lee introduced the use
of fluxes of molecules with well-defined direction and energy, molecular
beams. By crossing two such beams they could study details of the
reaction between molecules at extremely short times. Another important
method to investigate such reaction details is infrared chemiluminescence,
introduced by Polanyi. The emission of infrared radiation from the
reaction products gives information on the energy distribution in
the molecules.
3.4. Theoretical Chemistry and Chemical Bonding
Quantum mechanics, developed in the 1920s, offered
a tool towards a more basic understanding of chemical bonds. In
1927 Walter Heitler (1984-1981) and Fritz London (1900-1954) showed
that it is possible to solve exactly the relevant equations for
the hydrogen molecule ion, i.e., two hydrogen nuclei sharing a single
electron, and thereby calculate the attractive force between the
nuclei. For molecules containing more than three elementary particles,
even the hydrogen molecule with Lewis's two-electron bond (see Section
1.1), the equation can, however, not be solved exactly, so one has
to resort to approximate methods. A pioneer in developing such methods
was Linus Pauling (1901-1994) at California
Institute of Technology, who was awarded the Nobel Prize for Chemistry
in 1954 "for his research into the nature of the chemical bond...".
Pauling's valence-bond (VB) method is rigorously described in his
1935 book Introduction to Quantum Mechanics (written together
with E. Bright Wilson, Jr., at Harvard). A few years later (1939)
he published an extensive non-mathematical treatment in The Nature
of the Chemical Bond, a book which is one of the most read and
influential in the entire history of chemistry. Pauling was not
only a theoretician, but he also carried out extensive investigations
of chemical structure by X-ray diffraction (see Section 3.5). On
the basis of results with small peptides, which are building blocks
of proteins, he suggested the
-helix as an important structural element. Pauling was awarded
the Nobel Peace Prize for 1962, and he is the only person to date
to have won two unshared Nobel Prizes.
Pauling's VB method cannot give an adequate
description of chemical bonding in many complicated molecules, and
a more comprehensive treatment, the molecular-orbital (MO) method,
was introduced already in 1927 by Robert S. Mulliken (1896-1986)
from Chicago and later developed further by him as well as by many
other investigators. MO theory considers, in quantum-mechanical
terms, the interaction between all atomic nuclei and electrons in
a molecule. Mulliken also showed that a combination of MO calculations
with experimental (spectroscopic) results provides a powerful tool
for describing bonding in large molecules. Mulliken received the
Nobel Prize for Chemistry in 1966.
Theoretical chemistry has also contributed significantly
to our understanding of chemical reaction mechanisms. In 1981 the
Nobel Prize for Chemistry was shared between Kenichi
Fukui (1918-1998) in Kyoto and Roald
Hoffmann (1937- ) of Cornell University "for their theories,
developed independently, concerning the course of chemical reactions".
Fukui introduced in 1952 the frontier-orbital theory, according
to which the occupied MO with the highest energy and the unoccupied
one with the lowest energy have a dominant influence on the reactivity
of a molecule. Hoffmann formulated in 1965, together with Robert
B. Woodward (1917-1979) (see Section 3.8), rules, based on the
conservation of orbital symmetry, for the reactivity and stereochemistry
in chemical reactions.
Rudolph
A. Marcus (1923- ) published during ten years, starting in 1956,
a series of seminal papers on a comprehensive theory for the rates
electron-transfer reactions, the experimental study of which had
given Taube a Nobel Prize in 1983 (see Section 3.3). Marcus's theory
predicts how the rate varies with the driving force for the reaction,
i.e., the difference in energy between reactants and products, and
counter to intuition he found that it does not increase continuously,
but goes through a maximum, into the Marcus inverted region, which
has later been confirmed experimentally. Marcus was awarded the
Nobel Prize for Chemistry in 1992.
The latest Nobel Prize for work in theoretical
chemistry was given in 1998 to Walter
Kohn (1923- ) of Santa Barbara and John
A. Pople (1925- ) of Northwestern University (but a British
citizen). The prize to Kohn, a theoretical physicist, was based
on his development of density-functional theory, which facilitates
detailed calculations both of the geometrical structures of complex
molecules and of the energy map of chemical reactions. Pople, a
mathematician (but now Professor of Chemistry), was awarded "for
his development of computational methods in quantum chemistry".
In particular, Pople has designed computer programs based in classical
quantum theory as well as on density-functional theory.
3.5. Chemical Structure
The most commonly used method to determine the
structure of molecules in three dimensions is X-ray crystallography.
The diffraction of X-rays was discovered by Max
von Laue (1879-1960) in 1912, and this gave him the Nobel Prize
for Physics in 1914. Its use for the determination of crystal structure
was developed by Sir William Bragg (1862-1942) and
his son, Sir Lawrence Bragg (1890-1971),
and they shared the Nobel Prize for Physics in 1915. The first Nobel
Prize for Chemistry for the use of X-ray diffraction went to Petrus
(Peter) Debye (1984-1966), then of Berlin, in 1936. Debye did
not study crystals, however, but gases, which give less distinct
diffraction patterns. He also employed electron diffraction and
the measurement of dipole moments to get structural information.
Dipole moments are found in molecules, in which the positive and
negative charge is unevenly distributed (polar molecules).
Many Nobel Prizes have been awarded for the
determination of the structure of biological macromolecules (proteins
and nucleic acids). Proteins are long chains of amino-acids, as
shown by Emil Fischer (see Section 2), and the first step in the
determination of their structure is to determine the order (sequence)
of these building blocks. An ingenious method for this tedious task
was developed by Frederick
Sanger (1918- ) of Cambridge, and he reported the amino-acid
sequence for a protein, insulin, in 1955. For this achievement he
was awarded the Nobel Prize for Chemistry in 1958. Sanger
later (1980) received part of a second Nobel Prize for Chemistry
for a method to determine the nucleotide sequence in nucleic acids
(see Section 3.12), and he is the only scientist so far who has
won two Nobel Prizes for Chemistry.
The first protein crystal structures were reported
by Max Perutz (1914- ) and Sir
John Kendrew (1917-1997) in 1960, and these two investigators
shared the Nobel Prize for Chemistry in 1962. Perutz had started
studying the oxygen-carrying blood pigment, hemoglobin, with Sir
Lawrence Bragg in Cambridge already in 1937, and ten years later
he was joined by Kendrew, who looked at crystals of the related
muscle pigment, myoglobin. These proteins are both rich in Pauling's
-helix (see Section
3.4), and this made it possible to discern the main features of
the structures at the relatively low resolution first used. The
same year that Perutz and Kendrew won their prize, the Nobel Prize
for Physiology or Medicine went to Francis
Crick (1916- ), James
Watson (1928- ) and Maurice
Wilkins (1916- ) "for their discoveries concerning the
molecular structure of nucleic acids...". Two years later (1964)
Dorothy Crowfoot
Hodgkin (1910-1994) received the Nobel Prize for Chemistry for
determining the crystal structures of penicillin and vitamin B12.
Two later Nobel Prizes for Chemistry in the
crystallographic field were given for work on structures of relatively
small molecules. William N. Lipscomb (1919- ) of
Harvard received the prize in 1976 "for his studies on the
structures of boranes illuminating problems of chemical bonding".
In 1985 Herbert A.
Hauptman (1917- ) of Buffalo and Jerome
Karle (1918- ) of Washington, DC, shared the prize for "the
development of direct methods for the determination of crystal structures".
Their methods are called direct, because they yield the structure
directly from the diffraction data collected, and they have been
indispensable in the determination of the structures of a large
number of natural products.
Crystallographic electron microscopy was developed
by Sir Aaron Klug (1926- ) in Cambridge,
who was awarded the Nobel Prize for Chemistry in 1982. With this
technique Klug has investigated the structure of large nucleic acid-protein
complexes, such as viruses and chromatin, the carrier of the genes
in the cell nucleus. Many of the most important life processes are
carried out by proteins associated with biological membranes. This
is, for example, true of the two key processes in energy metabolism,
respiration and photosynthesis. Attempts to prepare crystals of
membrane proteins for structural studies were, however, for many
years unsuccessful, but in 1982 Hartmut Michel (1948- ), then
at the Max-Planck-Institut in Martinsried, managed to crystallize
a photosynthetic reaction center after a painstaking series of experiments.
He then proceeded to determine the three-dimensional structure of
this protein complex in collaboration with Johann Deisenhofer (1943- ) and
Robert Huber (1937- ), and this
was published in 1985. Deisenhofer, Huber and Michel shared the
Nobel Prize for Chemistry in 1988. Michel has later also crystallized
and determined the structure of the terminal enzyme in respiration,
and his two structures have allowed detailed studies of electron
transfer (cf. Sections 3.3 and 3.4) and its coupling to proton pumping,
key features of the chemiosmotic mechanism for which Peter Mitchell
had already received the Nobel Prize for Chemistry in 1978 (see
Section 3.12).
3.6. Inorganic and Nuclear Chemistry
Much of the progress in inorganic chemistry
during the 20th century has been associated with investigations
of coordination compounds, i.e., a central metal ion surrounded
by a number of coordinating groups, called ligands. In 1893 Alfred Werner (1866-1919) in Zürich
presented his coordination theory, and in 1905 he summarized his
investigations in this new field in a book (Neuere Anschauungen
auf dem Gebiete der anorganischen Chemie), which appeared in no
less than five editions 1905-1923. Compounds in which a metal ion
binds several other molecules (ligands), for example, ammonia, had
earlier been thought to have a linear structure, in accord with
a theory advanced by the Swedish chemist Wilhelm Blomstrand (1826-1862)
in Lund. Werner showed that such a structure is inconsistent with
some experimental facts, and he suggested instead that all the ligand
molecules are bound directly to the metal ion. Werner was awarded
the Nobel Prize for Chemistry in 1913. Taube's investigations of
electron transfer, awarded in 1983 (see Section 3.3), were mainly
carried out with coordination compounds, and vitamin B12
as well as the proteins hemoglobin and myoglobin, investigated by
the Laureates Hodgkin, Perutz and Kendrew (see Section 3.5), also
belong to this category.
Another early prize for work in inorganic chemistry
was that to Fritz Haber (1868-1934) from Berlin
in 1918 "for the synthesis of ammonia from its elements",
i.e., from nitrogen and hydrogen. The importance of this synthesis
is above all in its industrial application in the form of the Haber-Bosch
method, which had been developed by Carl Bosch (1874-1940) as an improvement
(cf. Nobel's will) of Haber's original procedure. It allows the
manufacture of ammonia on a large scale, and the ammonia can then
be used for the production of many different nitrogen-containing
chemicals. Bosch shared the Nobel Prize for Chemistry with Friedrich Bergius in 1931 (see
Section 3.13).
Much inorganic chemistry in the early 1900s
was a consequence of the discovery of radioactivity in 1896, for
which Henri Becquerel (1852-1908) from
Paris was awarded the Nobel Prize for Physics in 1903, together
with Pierre (1859-1906)
and Marie Curie
(1867-1934). In 1911 Marie
Curie received the Nobel Prize for Chemistry for her discovery
of the elements radium and polonium and for the isolation of radium
and studies of its compounds, and this made her the first investigator
to be awarded two Nobel Prizes. The prize in 1921 went to Frederick
Soddy (1877-1956) of Oxford for his work on the chemistry of
radioactive substances and on the origin of isotopes. In 1934 Frédéric Joliot
(1900-1958) and his wife Irène Joliot-Curie (1897-1956),
the daughter of the Curies, discovered artificial radioactivity,
i.e., new radioactive elements produced by the bombardment of non-radioactive
elements with -particles or neutrons. They were awarded the Nobel Prize for Chemistry
in 1935 for "their synthesis of new radioactive elements".
Many elements are mixtures of non-radioactive
isotopes (see Section 3.1), and in 1934 Harold
Urey (1893-1981) of Columbia University had been given the Nobel
Prize for Chemistry for his isolation of heavy hydrogen (deuterium).
Urey had also separated uranium isotopes, and his work was an important
basis for the investigations by Otto Hahn (1879-1968) from Berlin.
In attempts to make transuranium elements, i.e., elements with a
higher atomic number than 92 (uranium), by radiating uranium atoms
with neutrons, Hahn discovered that one of the products was barium,
a lighter element. Lise Meitner (1878-1968), at the time a refugee
from Nazism in Sweden, who had earlier worked with Hahn and taken
the initiative for the uranium bombardment experiments, provided
the explanation, namely, that the uranium atom was cleaved and that
barium was one of the products [3]. Hahn was awarded the Nobel Prize
for Chemistry in 1944 "for his discovery of the fission of
heavy nuclei", and it can be wondered why Meitner was not included.
Hahn's original intention with his experiments was later achieved
by Edwin M. McMillan (1907-1991)
and Glenn T. Seaborg (1912-1999) of
Berkeley, who were given the Nobel Prize for Chemistry in 1951 for
"discoveries in the chemistry of transuranium elements".
The use of stable as well as radioactive isotopes
have important applications, not only in chemistry, but also in
fields as far apart as biology, geology and archeology. In 1943 George de Hevesy
(1885-1966) from Stockholm received the Nobel Prize for Chemistry
for his work on the use of isotopes as tracers, involving studies
in inorganic chemistry and geochemistry as well as on the metabolism
in living organisms. The prize in 1960 was given to Willard F. Libby (1908-1980)
of the University of California, Los Angeles (UCLA), for his method
to determine the age of various objects (of geological or archeological
origin) by measurements of the radioactive isotope carbon-14.
3.7. General Organic Chemistry
Contributions in organic chemistry have led
to more Nobel Prizes for Chemistry than work in any other of the
traditional branches of chemistry. Like the first prize in this
area, that to Emil Fischer in 1902 (see Section 2), most of them
have, however, been awarded for advances in the chemistry of natural
products and will be treated separately (Section 3.9). Another large
group, preparative organic chemistry, has also been given its own
section (Section 3.8), and here only the prizes for more general
contributions to organic chemistry will be discussed. In 1969 the
Nobel Prize for Chemistry went to Sir Derek H. R. Barton (1918-1998)
from London, and Odd Hassel (1897-1991) from Oslo
for developing the concept of conformation, i.e., the spatial arrangement
of atoms in molecules, which differ only by the orientation of chemical
groups by rotation around a single bond. This stereochemical concept
rests on the original suggestion by van't Hoff of the tetrahedral
arrangement of the four valences of the carbon atom (see Section
2), and most organic molecules exist in two or more stable conformations.
The Nobel Prize for Chemistry in 1975 to Sir John Warcup Cornforth (1917-
) of the University of Sussex and Vladimir Prelog (1906-1998) of
ETH in Zürich was also based on research in stereochemistry.
Not only can a compound have more than one geometric form, but chemical
reactions can also have specificity in their stereochemistry, thereby
forming a product with a particular three-dimensional arrangement
of the atoms. This is especially true of reactions in living organisms,
and Cornforth has mainly studied enzyme-catalyzed reactions, so
his work borders onto biochemistry (Section 3.12). One of Prelog's
main contributions concerns chiral molecules, i.e., molecules that
have two forms differing from one another as the right hand does
from the left. Stereochemically specific reactions have great practical
importance, as many drugs, for example, are active only in one particular
geometric form.
Organometallic compounds constitute a group
of organic molecules containing one or more carbon-metal bond, and
they are thus the organic counterpart to Werner's inorganic coordination
compounds (see Section 3.6). In 1952 Ernst Otto Fischer (1918- ) and
Sir Geoffrey Wilkinson (1921-1996)
independently described a completely new group of organometallic
molecules, called sandwich compounds. In
such compounds a metal ion is bound not to a single carbon atom
but is "sandwiched" between two aromatic organic molecules.
Fischer and Wilkinson shared the Nobel Prize for Chemistry in 1973.
Work on the interaction of metal ions with organic
molecules was also recognized by the prize in 1987, which was shared
by Donald J. Cram (1919- ) of UCLA, Jean-Marie Lehn (1939- ) from
Strasbourg (and Paris) and Charles J. Pedersen (1904-1989)
of the Du Pont Company. These three investigators have synthesized
molecules with a ring structure, in which the hole in their middle
specifically recognizes and binds different metal ions. They can,
for example, distinguish between closely related ions, such as those
of sodium and potassium, and thus they mimic enzymes in their specificity.
The first such compound was synthesized by Pedersen in 1967, and
later Lehn and Cram developed increasingly sophisticated organic
compounds with cavities and cages in which not only metal ions but
other molecules are bound. This research has applications in the
whole spectrum of the chemical field, from inorganic chemistry to
biochemistry.
George
A. Olah (1927- ) from the University of Southern California
was awarded the Nobel Prize for Chemistry in 1994 "for his
contributions to carbocation chemistry". Already in the 1920s
and 1930s chemists had suggested that positively charged ions of hydrocarbons are
formed as short-lived intermediates in organic chemical reactions.
Such carbocations were, however, thought to be so reactive and unstable
that it would be impossible to prepare them in quantity. Olah's
investigations, starting in the 1960s, contradicted this supposition,
since he showed that stable carbocations can be prepared by the
use of a new type of extremely acidic compounds ("superacids"),
and carbocation chemistry now has a prominent position in all modern
textbooks of organic chemistry.
The preparation of a new form of carbon compounds
was also recognized by the Nobel Prize for Chemistry in 1996 to Robert F. Curl, Jr., (1933- )
of Rice University, Sir Harold W. Kroto (1939- ) of
the University of Sussex and Richard E. Smalley (1943- ) of
Rice University. These investigators had in 1985 discovered compounds,
called
fullerenes, in which 60 or 70 carbon atoms are bound together
in clusters in the form of a ball. The
designation fullerenes is taken from the name of an American architect,
R. Buckminster Fuller, who had designed a dome having the form of
a football for 1967 Montreal World Exhibition.
3.8. Preparative Organic Chemistry
One of the chief goals of the organic chemist
is to be able to synthesize increasingly complex compounds of carbon
in combination with various other elements, such as hydrogen, oxygen,
nitrogen, sulfur and phosphorus. The first Nobel Prize for Chemistry
recognizing pioneering work in preparative organic chemistry was
that to Victor Grignard
(1871-1935) in Nancy and Paul
Sabatier (1854-1941) from Toulouse in 1912. Grignard had discovered
that organic halides can form compounds with magnesium. These compounds,
now generally called Grignard reagents, are very reactive, and they
are consequently widely used for synthetic purposes. Sabatier was
given the prize for developing a method to hydrogenate organic compounds
in the presence of metallic catalysts. With his method oils can
be converted to saturated fats, and it is, for example, used for
margarine production and other industrial processes.
The prize in 1950 was presented to Otto Diels (1876-1954) from Kiel
and Kurt Alder (1902-1958) from Cologne
"for their discovery and development of the diene synthesis",
also called the Diels-Alder reaction. In this reaction, which was
developed already in 1928, organic compounds containing two double
bonds ("dienes") can effect the syntheses of many cyclic
organic substances. During the decades following the original work
several industrial applications of the Diels-Alder reaction have
been found, for example, in the production of plastics, which may
explain the lateness of the prize.
The German organic chemist Hans
Fischer (1881-1945) from Munich had already done significant
work on the structure of hemin, the organic pigment in hemoglobin,
when he synthesized it from simpler organic molecules in 1928. He
also contributed much to the elucidation of the structure of chlorophyll,
and for these important achievements he was awarded the Nobel Prize
for Chemistry in 1930 (cf. Section 3.5). He finished his determination
of the structure of chlorophyll in 1935, and by the time of his
death he had almost completed its synthesis as well.
Robert
Burns Woodward (1917-1979) from Harvard is rightly considered
the founder of the most advanced, modern art of organic synthesis.
He designed methods for the total synthesis of a large number of
complicated natural products, for example, cholesterol, chlorophyll
and vitamin B12. He received the Nobel Prize for Chemistry
in 1965, and he would probably have received a second chemistry
prize in 1981 for his part in the formulation of the Woodward-Hoffmann
rules (see Section 3.4), had it not been for his early death. Work
in synthetic organic chemistry was also recognized in 1979 with
the prize to Herbert C. Brown (1912- ) of Purdue
University and Georg Wittig (1897-1987) from
Heidelberg, who had developed the use of boron- and phosphorus-containing
compounds, respectively, into important reagents in organic synthesis.
Another master in chemical synthesis is Elias James Corey (1928- ) from
Harvard, who received the prize in 1990. He had made a brilliant
analysis of the theory of organic synthesis, which permitted him
to synthesize biologically active compounds of a complexity earlier
considered impossible.
The Nobel Prize for Chemistry in 1984 was given
to Robert Bruce Merrifield (1921-
) of Rockefeller University "for his development of methodology
for chemical synthesis on a solid matrix". Specifically, Merrifield
applied this ingenious idea to the synthesis of large peptides and
small proteins, for example, ribonuclease (cf. Section 3.12), but
the principle has later also been applied to nucleic acid chemistry.
In earlier methods each intermediate in the synthesis had to be
isolated, which resulted in a drastic drop in yield in syntheses
involving a large number of consecutive steps. In Merrifield's method
these isolation steps are replaced by a simple washing procedure,
which removes by-products as well as remaining starting materials,
and in this way substantial losses are avoided.
3.9. Chemistry of Natural Products
The synthesis of complex organic molecules must
be based on detailed knowledge of their structure. Early work on
plant pigments was carried out by Richard Willstätter (1872-1942),
a student of Adolf von Baeyer from Munich (see Section 2). Willstätter
showed a structural relatedness between chlorophyll and hemin, and
he demonstrated that chlorophyll contains magnesium as an integral
component. He also carried out pioneering investigations on other
plant pigments, such as the carotenoids, and he was awarded the
Nobel Prize for Chemistry in 1915 for these achievements. Willstätter's
work laid the ground for the synthetic accomplishments of Hans Fischer
(see Section 3.8). In addition, Willstätter contributed to
the understanding of enzyme reactions.
The prizes for 1927 and 1928 were both presented
to Heinrich Otto Wieland (1877-1957)
from Munich and Adolf Windaus (1876-1959) from
Göttingen, respectively, at the Nobel ceremony in 1928. These
two chemists had done closely related work on the structure of steroids.
The award to Wieland was primarily for his investigations of bile
acids, whereas Windaus was recognized mainly for his work on cholesterol
and his demonstration of the steroid nature of vitamin D. Wieland
had already in 1912, before his prize-winning work, formulated a
theory for biological oxidation, according to which removal of hydrogen
(dehydrogenation) rather than reaction with oxygen is the dominating
process.
Investigations on vitamins were recognized in
1937 and 1938 with the prizes to Sir
Norman Haworth (1883-1950) from Birmingham and Paul
Karrer (1889-1971) from Zürich and to Richard Kuhn (1900-1967) from
Heidelberg. Haworth did outstanding work in carbohydrate chemistry,
establishing the ring structure of glucose. He was the first chemist
to synthesize vitamin C, and this is the basis for the present large-scale
production of this nutrient. Haworth shared the prize with Karrer,
who determined the structure of carotene and of vitamin A. Kuhn
also worked on carotenoids, and he published the structure of vitamin
B2 at the same time as Karrer. He also isolated vitamin
B6. In 1939 the Nobel Prize for Chemistry was shared
between Adolf Butenandt (1903-1995) from
Berlin and Leopold Ruzicka (1887-1976) of
ETH. Butenandt was recognized "for his work on sex hormones",
having isolated estrone, progesterone and androsterone. Ruzicka
synthesized androsterone and also testosterone.
The awards for outstanding work in natural-product
chemistry continued after World War II. In 1947 Sir
Robert Robinson (1886-1975) from Oxford received the prize for
his studies on plant substances, particularly alkaloids, such as
morphine. Robinson also synthesized steroid hormones, and he elucidated
the structure of penicillin. Many hormones are of a polypeptide
nature, and in 1955 Vincent du Vigneaud (1907-1997)
of Cornell University was given the prize for his synthesis of two
such hormones, vasopressin and oxytocin. Finally, in this area, Alexander R. Todd
(Lord Todd since 1962) (1907-1997) was recognized in 1957 "for
his work on nucleotides and nucleotide co-enzymes". Todd had
synthesized ATP (adenosine triphosphate) and ADP (adenosine diphosphate),
the main energy carriers in living cells, and he determined the
structure of vitamin B12 (cf. Section 3.5) and of FAD
(flavin-adenine dinucleotide).
3.10. Analytical Chemistry and Separation Science
Inorganic chemists, organic chemists and biochemists
develop analytical methods as part of their regular research. It
is consequently natural that not many Nobel Prizes have been awarded
for contributions specifically in analytical chemistry. One such
prize was, however, that to Fritz Pregl (1869-1930) from Graz
in 1923 for his development of organic microanalysis. The medical
biochemist from Uppsala, Olof Hammarsten (1841-1932), who gave the
presentation speech as Chairman of the Nobel Committee for Chemistry,
stressed that Pregl's work constituted an improvement rather than
a discovery, in accord with Nobel's will. Pregl modified existing
methods for quantitative elemental analysis of organic substances
to handle very small quantities, which saved time, labor and expense.
Another prize in analytical chemistry was given to Jaroslav
Heyrovsky (1890-1967) from Prague in 1959 for his development
of polarographic methods of analysis. In these a dropping mercury
electrode is employed to determine current-voltage curves for electrolytes.
A given ion reacts at a specific voltage, and the current is a measure
of the concentration of this ion.
The analysis of macromolecular constituents
in living organisms requires specialized methods of separation.
One such method is ultracentrifugation, developed by The
Svedberg (1884-1971) from Uppsala a few years before he was
awarded the Nobel Prize for Chemistry in 1926 "for his work
on disperse systems" (see Section 3.11). Svedberg's student, Arne Tiselius
(1902-1971), studied the migration of protein molecules in an electric
field, and with this method, named electrophoresis, he demonstrated
the complex nature of blood proteins. Tiselius also refined adsorption
analysis, a method first used by the Russian botanist, Michail Tswett
(1872-1919), for the separation of plant pigments and named chromatography
by him. In 1948 Tiselius was given the prize for these achievements.
A few years later (1952) Archer J.P. Martin (1910- ) from
London and Richard L.M. Synge (1914-1994)
from Bucksburn (Scotland) shared the prize "for their invention
of partition chromatography", and this method was a major tool
in many biochemical investigations later awarded with Nobel Prizes
(see Section 3.12).
3.11. Polymers and Colloids
Polymeric substances in solution, including
life constituents, such as proteins and polysaccharides, are in
a colloidal state, i.e., they exist as suspensions of particles
one millionth to one thousandth of a centimeter in size. In the
case of the biological polymers the individual molecules are so
large that they form a colloidal suspension, but many other substances
can be obtained in a colloidal state. A much-studied example is
aggregates of gold atoms, and the Nobel Prize for Chemistry for
1925 was given to Richard Zsigmondy (1865-1929)
from Göttingen for demonstrating the heterogeneous nature of
such gold sols. He did this with the aid of an instrument, the ultramicroscope,
which he had developed in collaboration with scientists at the Zeiss
factory in Jena. With this instrument the particles and their motion
can be observed by the light they scatter at a right angle to the
direction of the illuminating light beam. Early work in colloid
chemistry had also been carried out by Wolfgang Ostwald (1883-1943),
son of the 1909 Laureate Wilhelm Ostwald, but this was not of a
caliber earning him a Nobel Prize.
The Svedberg who received the Nobel Prize for
Chemistry in 1926, also investigated gold sols. He used Zsigmondys
ultramicroscope to study the Brownian movement of colloidal particles,
so named after the Scottish botanist Robert Brown (1773-1858), and
confirmed a theory developed by Albert Einstein (1859-1955) in 1905
and, independently, by M. Smoluchowski. His greatest achievement
was, however, the construction of the utracentrifuge, with which
he studied not only the particle size distribution in gold sols
but also determined the molecular weight of proteins, for example,
hemoglobin. In the same year as Svedberg got the prize the Nobel
Prize for Physics was awarded to Jean
Baptiste Perrin (1870-1942) of Sorbonne for developing equilibrium
sedimentation in colloidal solutions, a method which Svedberg later
perfected in his ultracentrifuge. Svedberg's investigations with
the ultracentrifuge and Tiselius's electrophoresis studies (see
Section 3.10) were instrumental in establishing that protein molecules
have a unique size and structure, and this was a prerequisite for
Sanger's determination of their amino-acid sequence and the crystallographic
work of Kendrew and Perutz (see Section 3.5).
In the 1920s Hermann
Staudinger (1881-1965) from Freiburg developed the concept of
macromolecules. He synthesized many polymers, and he showed that
they are long chain molecules. The large plastic industry is largely
based on Staudinger's work. In 1953 he received the Nobel Prize
for Chemistry "for his discoveries in the field of macromolecular
chemistry". The prize in 1963 was shared by Karl Ziegler (1898-1973) of the
Max-Planck-Institute in Mülheim and Giulio Natta (1903-1979) from
Milan for their discoveries in polymer chemistry and technology.
Ziegler demonstrated that certain organometallic compounds (see
Section 3.7) can be used to effect polymerization reactions, and
Natta showed that Ziegler catalysts can produce polymers with a
highly regular three-dimensional structure. The latest Nobel Prize
for contributions in polymer chemistry was given to Paul
J. Flory (1910-1985) of Stanford in 1974. Flory carried out
fundamental theoretical as well as experimental investigations of
the physical chemistry of macromolecules, but his work also led
to such important polymers as nylon and synthetic rubber.
3.12. Biochemistry
The second Nobel Prize for discoveries in biochemistry
came in 1929, when Sir Arthur Harden (1865-1940)
from London and Hans von Euler-Chelpin (1873-1964)
from Stockholm shared the prize for investigations of sugar fermentation,
which formed a direct continuation of Buchner's work awarded in
1907. With his young co-worker, William John Young (1878-1942),
Harden had shown in 1906 that fermentation requires a dialysable
substance, called co-zymase, which is not destroyed by heat. Harden
and Young also demonstrated that the process stops before all sugar
(glucose) has been used up, but it starts again on addition of inorganic
phosphate, and they suggested that hexose phosphates are formed
in the early steps of fermentation. von Euler had done important
work on the structure of co-zymase, shown to be nicotinamide adenine
dinucleotide (NAD, earlier called DPN). As the number of Laureates
can be three, it may seem appropriate for Young to have been included
in the award, but Euler's discovery was published together with
Karl Myrbäck (1900-1985), and the number of Laureates is limited
to three.
The next biochemical Nobel Prize was given in
1946 for work in the protein field. James
B. Sumner (1887-1955) of Cornell University received half the
prize "for his discovery that enzymes can be crystallized"
and John H. Northrop (1891-1987) together
with Wendell M. Stanley (1904-1971),
both of the Rockefeller Institute, shared the other half "for
their preparation of enzymes and virus proteins in a pure form".
Sumner had in 1926 crystallized an enzyme, urease, from jack beans
and suggested that the crystals were the pure protein. His claim
was, however, greeted with great scepticism, and the crystals were
suggested to be inorganic salts with the enzyme adsorbed or occluded.
Just a few years after Sumner's discovery Northrop, however, managed
to crystallize three digestive enzymes, pepsin, trypsin and chymotrypsin,
and by painstaking experiments shown them to be pure proteins. Stanley
started his attempt to purify virus proteins in the 1930s, but not
until 1945 did he get virus crystals, and this then made it possible
to show that viruses are complexes of protein and nucleic acid.
The pioneering studies of these three investigators form the basis
for the enormous number of new crystal structures of biological
macromolecules, which have been published in the second half of
the 20th century (cf. Section 3.5).
Several Nobel Prizes for Chemistry have been
awarded for work in photosynthesis and respiration, the two main
processes in the energy metabolism of living organisms (cf. Section
3.5). In 1961 Melvin Calvin (1911-1997) of Berkeley
received the prize for elucidating the carbon dioxide assimilation
in plants. With the aid of carbon-14 (cf. Section 3.6) Calvin had
shown that carbon dioxide is fixed in a cyclic process involving
several enzymes. Peter
Mitchell (1920-1992) of the Glynn Research Laboratories in England
was awarded in 1978 for his formulation of the chemiosmotic theory.
According to this theory, electron transfer (cf. Sections 3.3 and
3.4) in the membrane-bound enzyme complexes in both respiration
and photosynthesis, is coupled to proton translocation across the
membranes, and the electrochemical gradient thus created is used
to drive the synthesis of ATP (adenosine triphosphate), the energy
storage molecule in all living cells. Paul
D. Boyer (1918- ) of UCLA and John
Walker (1941- ) of the MRC Laboratory in Cambridge shared one
half of the 1997 prize for their elucidation of the mechanism of
ATP synthesis; the other half of the prize went to Jens
Skou (1918- ) in Aarhus for the first discovery of an ion-transporting
enzyme. Walker had determined the crystal structure of ATP synthase,
and this structure confirmed a mechanism earlier proposed by Boyer,
mainly on the basis of isotopic studies.
Luis
F. Leloir (1906-1987) from Buenos Aires was awarded in 1970
"for the discovery of sugar nucleotides and their role in the
biosynthesis of carbohydrates". In particular, Leloir had elucidated
the biosynthesis of glycogen, the chief sugar reserve in animals
and many microorganisms. Two years later the prize went with one
half to Christian B. Anfinsen (1916-1995)
of NIH and the other half shared by Stanford Moore (1913-1982) and
William H. Stein (1911-1980),
both from Rockefeller University, for fundamental work in protein
chemistry. Anfinsen had shown, with the enzyme ribonuclease, that
the information for a protein assuming a specific three-dimensional
structure is inherent in its amino-acid sequence, and this discovery
was the starting point for studies of the mechanism of protein folding,
one of the major areas of present-day biochemical research. Moore
and Stein had determined the amino-acid sequence of ribonuclease,
but they received the prize for discovering anomalous properties
of functional groups in the enzyme's active site, which is a result
of the protein fold.
Naturally a number of Nobel Prizes for Chemistry
have been given for work in the nucleic acid field. In 1980 Paul Berg (1926- ) of Stanford
received one half of the prize for studies of recombinant DNA, i.e.,
a molecule containing parts of DNA from different species, and the
other half was shared by Walter Gilbert (1932- ) from Harvard
and Frederick Sanger (see Section 3.5) for developing methods for
the determination of the base sequences of nucleic acids. Berg's
work provides the basis of genetic engineering, which has led to
the large biotechnology industry. Base sequence determinations are
essential steps in recombinant-DNA technology, which is the rationale
for Gilbert and Sanger sharing the prize with Berg. Sidney Altman (1939- ) of Yale
and Thomas R. Cech (1947- ) of the
University of Colorado shared the prize in 1989 "for their
discovery of the catalytic properties of RNA". The central
dogma of molecular biology is: DNA > RNA > enzyme.
The discovery that not only enzymes but also RNA possesses catalytic
properties have led to new ideas about the origin of life. The 1993
prize was shared by Kary B. Mullis (1944- ) from La
Jolla and Michael Smith (1932- ) from Vancouver,
who both have given important contributions to DNA technology. Mullis
developed the PCR ("polymerase chain reaction") technique,
which makes it possible to replicate millions of times a specific
DNA segment in a complicated genetic material. Smith's work forms
the basis for site-directed mutagenesis, a technique by which it
is possible to change a specific amino-acid in a protein and thereby
illuminate its functional role.
3.13. Applied Chemistry
A few Nobel Prizes for Chemistry have recognized
contributions outside the conventional basic chemical fields. The
prize in 1931 went to Carl Bosch (1874-1940) and Friedrich Bergius (1884-1949),
both from Heidelberg, "for the invention and development of
chemical high pressure methods". Bosch had modified Haber's
method for ammonia synthesis (see Section 3.6) to make it suitable
for large-scale industrial use. Bergius used high-pressure methods
to prepare oil by the hydrogenation of coal, and Bosch, like Bergius
working at the large concern I.G. Farben, later improved the procedure
by finding a good catalyst for the Bergius process.
Work in agricultural and nutritional chemistry
led to the award of Artturi Ilmari Virtanen (1895-1973)
from Helsinki in 1945. The citation particularly stressed his development
of the AIV method, so named after the inventor's initials. Virtanen
had first carried out biochemical studies of nitrogen fixation by
plants with the aim of producing protein-rich crops. He then found
that the fodder could be preserved with the aid of a mixture of
sulfuric and nitric acid (AIV acid).
Finally, basic work in atmospheric and environmental
chemistry was recognized in 1995 with the prize to Paul
Crutzen (1933- ), from the Netherlands, but working at the Max-Planck-Institute
in Mainz, Mario Molina
(1943- ) of MIT and F.
Sherwood Rowland (1927- ) of Irvine. These three investigators
have studied in detail the chemical processes leading to the formation
and decomposition of ozone in the atmosphere. In particular, they
have shown that the atmospheric ozone layer is very sensitive to
emission chemicals produced by human activity, and these discoveries
have led to international legislation.
4. Concluding Remarks
The first hundred years of Nobel Prizes for
Chemistry give a beautiful picture of the development of modern
chemistry. The prizes cover the whole spectrum of the basic chemical
sciences, from theoretical chemistry to biochemistry, and also a
number of contributions to applied chemistry. From a quantitative
point of view, organic chemistry dominates with no less than 25
awards. This is not surprising, since the special valence properties
of carbon result in an almost infinite variation in the structure
of organic compounds. Also, a large number of the prizes in organic
chemistry were given for investigations of the chemistry of natural
products of increasing complexity and thus are on the border to
biochemistry.
As many as 11 prizes have been awarded for
biochemical discoveries. Even if the first biochemical prize was
given already in 1907 (Buchner), only three awards in this area
came in the first half of the century, illustrating the explosive
growth of biochemistry in recent decades (8 prizes in 1970-1997).
At the other end of the chemical spectrum, physical chemistry, including
chemical thermodynamics and kinetics, dominates with 13 prizes,
but there has also been 6 prizes in theoretical chemistry. Chemical
structure is another large area with 8 prizes, including awards
for methodological developments as well as for the determination
of the structure of large biological molecules or molecular complexes.
Industrial chemistry was first recognized in 1931 (Bergius, Bosch),
but many more recent prizes for basic contributions lie close to
industrial applications, for example, those in polymer chemistry.
Science is a truly international undertaking,
but the western dominance of the Nobel scene is striking. No less
than 46 scientists in the United States have received the Nobel
Prize for Chemistry, but the majority have been given the prize
after World War II. The first US prize was awarded in 1915 (for
1914, Richards), and only two more Americans got the prize before
1946 (Langmuir in 1932, Urey in 1934). German chemists form the
second most awarded group with 26 Laureates, but 14 of these received
the prize before 1945. Of the 25 British investigators recognized,
on the other hand, no less than 19 got the prize in the second half
of the century. France has 7 Laureates in chemistry, Sweden and
Switzerland 5 each, and the Netherlands and Canada 3. One prize
winner each is found in the following countries: Argentina, Austria,
Belgium, Czechoslovakia, Denmark, Finland, Italy, Japan, Norway
and Russia.
Extrapolating the trend of the 20th century
Nobel Prizes for Chemistry, it is expected that in the 21st century
theoretical and computational chemistry will flourish with the aid
of the expansion of computer technology. The study of biological
systems may become more dominant and move from individual macromolecules
to large interactive systems, for example, in chemical signaling
and in neural function, including the brain. And it is to be hoped
that the next century will witness a wider national distribution
of Laureates.
References
1. A. Westgren, in: W. Odelberg (Ed.), "Nobel
the Man and His Prizes", Elsevier, New York, 1972, pp.
279-385.
2. D. Kormos Barkan, "Walther Nernst and the Transition in
Modern Physical Science", Cambridge University Press, 1999.
3. Patricia Rife, "Lise Meitner and the Dawn of the Nuclear
Age", Birkhäuser, 1999.
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