Linus Pauling

A Portland boy with a chemistry set

Linus Carl Pauling was born on 28 February 1901 in Portland, Oregon, the firstborn child of a pharmacist who died when Linus was nine. He fell in love with chemistry at twelve, after a friend showed him a chemistry set, and he built his own out of glass jars and scraps from a closed steel mill. He left high school without a diploma (he had refused a required American-history class) and rode the train down to Oregon Agricultural College. The college issued the missing diploma in 1962, the year he won his second Nobel.

Caltech and the new mechanics

Pauling went south to Caltech in 1922, finished his PhD in three years, and won a Guggenheim Fellowship to Europe at twenty-five. He spent 1926 with Arnold Sommerfeld in Munich, Erwin Schrödinger in Zurich, and Niels Bohr in Copenhagen, arriving in Munich just as Schrödinger’s wave equation appeared. Unlike the older chemists who had grown up on Lewis-dot diagrams, he absorbed quantum mechanics as his native tongue.

Between 1928 and 1935 he wrote a sequence of papers that turned chemistry into an applied branch of quantum mechanics: hybrid orbitals in 1931, the concept of electronegativity, the partial-double-bond character of the peptide bond, and the rules that still bear his name for predicting ionic crystal structures. In 1939 Cornell University Press published The Nature of the Chemical Bond and the Structure of Molecules and Crystals. It was textbook, research monograph, and manifesto in one volume: how sp, sp², and sp³ hybridization explained the tetrahedral carbon; how resonance between contributing structures gave benzene its stability; how electronegativity differences set bond polarity on a quantitative scale.

In the late 1920s, Pauling began publishing papers on the nature of the chemical bond. Between 1937 and 1938, he took a position as George Fischer Baker Non-Resident Lecturer in Chemistry at Cornell University. While at Cornell, he delivered a series of nineteen lectures and completed the bulk of his famous textbook The Nature of the Chemical Bond. It is based primarily on his work in this area that he received the Nobel Prize in Chemistry in 1954 "for…

The Nobel committee cited that work when it gave him the 1954 Chemistry Prize “for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances.”

The α-helix on a slip of paper

In the spring of 1948 Pauling was visiting Oxford and came down with a cold. Confined to bed, bored, he asked for paper and a pencil and began folding a strip to model a polypeptide chain, respecting the planar peptide bond he had argued for years earlier. By the time the fever broke he had the α-helix: 3.6 amino acids per turn, hydrogen bonds running parallel to the helical axis, the backbone wound into a right-handed spring. He published with Robert Corey and Herman Branson in early 1951, and the structure was, in detail, correct.

The same intuition nearly delivered DNA. In February 1953 he and Corey published a triple-helix model with the phosphate backbone on the inside, a structure wrong in a way an undergraduate organic chemist could have caught. James Watson and Francis Crick, reading the preprint at the Cavendish, realised the great man had stumbled and accelerated their own work. Two months later they had the double helix. Pauling, who could not get a passport because the State Department considered him a security risk, never saw the King’s College X-ray photographs that would have set him straight.

The Peace Prize the State Department tried to prevent

The bomb changed Pauling. He had stayed out of politics during the war (he turned down the directorship of the Manhattan Project’s chemistry division) but Hiroshima and Nagasaki made him a public moralist for the rest of his life. He campaigned against atmospheric nuclear testing, calculating with care how many cases of leukaemia and how much genetic damage each megaton produced. In 1958 he and his wife Ava Helen presented the United Nations with a petition signed by 11,021 scientists from 49 countries demanding an end to nuclear tests.

The aftermath of the Manhattan Project and his wife Ava's pacifism changed Pauling's life profoundly, and he became a peace activist. In June 1945, a "May-Johnson Bill" began that would become the Atomic Energy Act of 1946 (signed August 1, 1946). In November 1945, Pauling spoke to the Independent Citizens Committee of the Arts, Sciences and Professions (ICCASP) on atomic weapons; shortly after, wife Ava and he…

The Limited Test Ban Treaty went into effect on 10 October 1963. The same day the Nobel Foundation announced that Pauling would receive the 1962 Peace Prize. He is the only person to have won two unshared Nobel Prizes, and the second came in the teeth of a campaign by Life magazine, which had called him “weird” and “a fellow traveler”, and the FBI, which had a file on him running to thousands of pages.

Vitamin C and the long late chapter

The last act is harder. From the late 1960s onward Pauling became convinced that very large doses of vitamin C could prevent or shorten the common cold and treat advanced cancer. Clinical trials his clinic ran with the surgeon Ewan Cameron produced results that the Mayo Clinic, repeating the work under more rigorous controls, could not reproduce. The bulk of the medical community concluded that megadose vitamin C does roughly nothing for cancer survival, possibly a little for the duration of colds. Pauling never accepted this and went on prescribing himself grams a day. He died of prostate cancer in 1994, at home in Big Sur, aged 93.

What he means to the quantum story

Pauling carried quantum mechanics out of the hydrogen atom and into the real, dirty world of molecules, crystals, and proteins. Before him, chemistry was an empirical art with a puzzling new physics nibbling at its edges. After him, the sp³ tetrahedron and the p-orbital double bond were as standard a piece of mental furniture for a first-year chemistry student as the covalent bond itself.