ScienceWeek

LINUS PAULING (1901-1994)

In every century, every field in science has its personal "tour de force", an individual with enormous intellect and prodigious research output who pushes the field to new boundaries. In 20th century chemistry, it can be argued that such an individual was Linus Pauling (1901-1994).

On the theoretical front, Pauling was largely responsible for the immensely successful extrapolation from quantum physics to chemistry. On the experimental front, Pauling investigated molecular structures using quantum mechanics, x-ray diffraction, electron diffraction, magnetic effects, and heats of reaction to calculate interatomic distances in molecule and the angles between chemical bonds. He introduced the concepts of hybrid orbitals, directed valency, the partial ionic character of covalent bonds, and resonance of molecular structure. His book /The Nature of the Chemical Bond and the Structure of Molecules and Crystals/ was the most influential chemical text in the 20th century. When he moved into biochemistry, Pauling did important work on the structure of proteins and the molecular basis of sickle cell anemia. He received the Nobel Prize in Chemistry in 1954.

During the last 30 years of his life, Pauling attempted to break new ground in several other areas in medical biology, including a theory of anesthesia and the use of high doses of vitamin C in the prevention and treatment of the common cold, but these attempts proved dead ends. Many people were saddened to see the last few decades of Pauling's life clouded by what appeared to be an almost obsessive search for acclamation. Most biologists and clinicians never took his vitamin C proposals seriously. As for his theory of anesthesia, Pauling apparently never understood that there are many ways to reversibly shut down nerve cells, so that advocating a single mechanism for all types of anesthesia is not justified. He certainly did not understand the paramount physiological difference between general anesthesia and local anesthesia. But no matter these failures during his later years, Pauling certainly stands as a formidable colossus of 20th century chemistry.

The following points are made by Gautam R. Desiraju (Nature 2000 408:407):

1) The author suggests that it was only when the idea of electron sharing was accepted and quantified that the chemical bond came into its very own. After that, "chemistry had no further need of physics for the rest of the century." This extrapolation from physics to chemistry and the articulation of chemistry as an independent subject was the handiwork of a single individual. "Linus Pauling ranks with Galileo, Da Vinci, Shakespeare, Newton, Bach, Faraday, Freud, and Einstein as one of the great thinkers and visionaries of the millennium. Truly he was not of his age, but for all time."

2) The author suggests that, in retrospect, it appears that chemistry was waiting for Pauling. His chapters in /The Nature of the Chemical Bond and the Structure of Molecules and Crystals/proceed almost ruthlessly through interatomic distances, electronegativity, ionic, covalent, and van der Waals radii, aromaticity and the structure of benzene, multiple bonds, electron deficient substances, the metallic bond and the hydrogen bond. "They were a route map for chemical research for the rest of the century."

3) The author suggests that chemistry is utterly different from physics and biology in its dependence, at a primal level, on just one scientist, and that this raises some awkward questions. Did Pauling's influence modify, divert, or even stunt the development of other, perhaps still unexplored or unidentified, branches of the subject? Are chemists introverted and cautious because much of their research flows from a single stream of consciousness, making big imaginative leaps unnecessary? Does chemistry lack the high drama of physics and the glamor of biology because these were appropriated by one larger than life individual? The author concludes: "Chemistry will become a different subject as it transforms from a unitary to a diversified science. Will it ultimately delocalize and dissolve into other disciplines? Only time will tell, but if it does, it would only be because its very identity depended for so long on the contributions of a single individual."