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O

CTOBER

2002 T

ODAY


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HEMIST AT

W

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51

©2002 A


MERICAN

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HEMICAL



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OCIETY


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TO COURTES



Y OF RO

ALD H


OFFMANN

I

n high school, chemistry was not

one of Kenichi Fukui’s favorite subjects.

He loved mathematics, and was also

considered a literary scholar, known for his

great love of books and languages. But in

1981, Fukui became the first Japanese

scientist to receive the Nobel Prize in Chem-

istry, for his frontier orbital theory of chem-

ical reactivity. Based on his research on

the specific properties of electronic orbitals,

Fukui’s theory transformed scien-

tists’ ability to predict the routes

and products of chemical reactions.

Born in Nara, Japan, in 1918,

Fukui was the eldest of three sons

born to Ryokichi and Chie Fukui.

His father, Ryokichi, was a foreign

trade merchant and factory manag-

er. Although he was not enam-

ored of chemistry, Fukui took the

advice of a respected professor and

entered the Department of Indus-

trial Chemistry at Kyoto Universi-

ty, thus beginning a lifelong affil-

iation with the school. After

obtaining a B.A. in engineering in

1941, he accepted a position with

the Japanese Army Fuel Laboratory, where

he participated in Japan’s World War II

effort by developing synthetic fuels. He

returned to Kyoto University in 1943 and

became a lecturer in the Fuel Chemistry

Department. 

Simultaneously, he began work on his

doctoral degree. Rising through the academ-

ic ranks, he became an assistant professor

in 1945, received his Ph.D. in chemical

engineering in 1948, and achieved the rank

of full professor in 1951. 

Although Fukui was trained as an engi-

neer and had done applied fuel research,

he developed an interest in quantum chem-

istry. He became a largely self-taught theo-

retician and actively pursued this interest

soon after returning to Kyoto University.

By 1956, Fukui had gathered around him

a group of experimentalists and theoreti-

cians who went on to produce more than

450 papers over the next 30 years, among

which were some that dealt with the

electronic theory of organic reactions. Other

papers were about the statistical theory of

gelation, organic synthesis by inorganic

salts, and polymerization kinetics and cata-

lysts. Fukui also continued to work in exper-

imental organic chemistry and published

137 papers on the subject between 1944

and 1972.

“Delightful Discovery”

In 1952, Fukui published the first paper

detailing his theoretical work on the rela-

tionship between molecular orbitals (MO)

and chemical reactivity. He had found a

correlation between the frontier electron

density and the chemical reactivity in

aromatic hydrocarbons (he referred to this

as a “delightful discovery”). This paper

provided a simplified theoretical basis for

American Nobel Laureate Robert Mulliken’s

findings on charge transfer and electron

donor acceptors in complex chemical struc-

tures. Fukui believed that a reaction should

occur at the position of largest electron

density in the frontier (highest occupied

or lowest unoccupied) orbitals. Because

many experimental chemists at that time

did not have the necessary mathematical

background to understand its potential,

and because many theoretical chemists

thought the idea too simplistic, the paper

was largely ignored.

Undeterred, Fukui and his colleagues

continued to broaden their theories and

experiments and published two more impor-

tant papers in 1954. In the first of these

papers, Fukui included nucleophilic and

free-radical attack on conjugated hydro-

carbons in his methods. He showed that

these could be correlated respectively with

the substrate position having the great-

est virtual electron density—the lowest

unoccupied molecular orbital (which was

later called LUMO). 

In the mid-1960s, Fukui and

Roald Hoffmann (a Polish-born

American chemist) discovered—

almost simultaneously and inde-

pendently of each other—that

symmetry properties of frontier

orbitals could explain certain reac-

tion courses that had previously

been difficult to understand. This

gave rise to unusually intensive

research activity—both theoreti-

cal and practical—in many parts

of the world.

Fukui developed the theory that

during chemical reactions molecules

share loosely bonded electrons,

which occupy so-called frontier

orbitals. This theory advanced the under-

standing of the mechanism of chemical

reactions, especially in the production of

organic compounds. Fukui showed that

certain properties of the orbits of the most

loosely bound electrons and of the “most

easily accessible” unoccupied electronic

orbitals (which he called “frontier orbitals”)

had unexpected significance for the chem-

ical reactivity of molecules. 

Building on his frontier orbital research,

Fukui expanded his research into formu-

lating the path of chemical reactions, and

he published his first paper on the topic

in 1970. In his autobiography listed on the

Nobel website (www.nobel.se/chemistry/



laureates/1981/fukui-autobio.html), he

commented on the findings in this paper:

“This simple idea served to provide infor-

mation on the geometrical shape of react-

ing molecules, and I was able to make the

C h e m i s t r y   C h r o n i c l e s

J

ULIE

L. M

C

D

OWELL

AND

J

ULIA

B

ELCHER

Fukui’s Frontiers

The first Japanese scientist to win a Nobel Prize

introduced the concept of frontier orbitals.

Kenichi Fukui at a 1981 Nobel Prize committee reception.



role of the frontier orbitals in chemical

reactions more distinct through visualiza-

tion, by drawing their diagrams.”

Fukui shared the 1981 Nobel Prize in

Chemistry with Roald Hoffmann for their

theories on the course of chemical reac-

tions. Known for his calm demeanor, Fukui

was said to be gracious but composed when

informed that he won this prestigious prize.

“I am just another chemist scholar,” he said,

and feared that the publicity would disrupt

his commitment to a peaceful existence. 

Although his earliest paper outlining

the theories of frontier orbitals was ignored,

Fukui’s (and Hoffmann’s) method of attack-

ing difficult and complicated problems

succeeded because they made generaliza-

tions through simplifications. Today, their

method of conceiving the course of chem-

ical reactions is used by, among others,

chemists studying life processes and

chemists making new drugs. Pharmaceuti-

cal and fine chemical companies use Fukui’s

ideas and methods to predict optimum

conditions for a particular reaction path-

way and to minimize unwanted side reac-

tions. This level of analysis enables phar-

maceutical and chemical manufacturers to

yield highly specific and pure products. 

Honors Accrue

By the end of the 1960s, Fukui had earned

an international reputation as a respect-

ed scientist. In 1970, he taught at the

Illinois Institute of Technology as a Nation-

al Science Foundation senior foreign scien-

tist. In 1981, the year he won the Nobel

Prize, he was named a foreign fellow of the

National Academy of Science. The follow-

ing year, Fukui was named both professor

emeritus of Kyoto University and president

of the Kyoto Institute of Technology. He

served as president of the Chemical Soci-

ety of Japan from March 1983 to Febru-

ary 1984. In addition, Fukui was known

for his efforts to promote science educa-

tion in Japan during the later years of his

life and was the director of the Institute

for Fundamental Chemistry (Kyoto) from

1988 to 1998.

Fukui died of cancer at the age of 79

in January 1998. His obituary in The



Independent, a London newspaper, remem-

bers Fukui as a “modest, retiring man who

hated any kind of publicity. He led a

quiet life with his family and a few friends,

with whom he loved to drink sake and to

play music, for he was an excellent singer

of French and German songs.” 

“I must confess that, when I was writ-

ing the 1952 paper, I never imagined I

would be coming to Stockholm to receive

the Nobel Prize 30 years later,” he wrote

in his autobiography. “The possibility

became a reality through the good circum-

stances in which I found myself: with my

teachers, my colleagues and students,

and of course, my parents and family.”



Further Reading

Fukui, K., Fujimoto, H., Eds. Frontier Orbitals and



Reaction Paths: Selected Papers of Kenichi Fukui;

World Scientific Publishing Co.: Singapore, 1997.

Autobiographical sketch for the Nobel e-Museum;

www.nobel.se/chemistry/laureates/1981/

fukui-autobio.html.

Julie L. McDowell is an assistant editor

and Julia Belcher is an associate editor

of Today’s Chemist at Work. Send your

comments or questions about this article to

tcaw@acs.org or to the Editorial Office

address on page 6. 

52 T

ODAY


S

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HEMIST AT

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2002

www.tcawonline.org



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