Ingold , Sir Christopher Kelk

(1893–1970) British chemist

Ingold, a Londoner, was educated at the University of Southampton and at Imperial College, London. After serving as professor of organic chemistry at the University of Leeds from 1924 until 1930, he moved to the chair of chemistry at University College, London, where he remained until his retirement in 1961.

With over 400 papers to his credit and as the author of the classic text, Structure and Mechanism in Organic Chemistry (1953), Ingold was one of the leading figures in British chemistry. The basic aim running through all his work was to understand the mechanism of organic reactions, particularly the kinetics of elimination and substitution reactions. In 1926 he introduced the idea of mesomerism, fully explained in his paper Principles of an Electronic Theory of Organic Reactions (1934). This was similar to the concept of resonance proposed by Linus Pauling in the early 1930s. The basic idea was that if a molecule could exist in two electronic structures then its normal state was neither one nor the other but some ‘hybrid’ form. This theory was substantiated by measuring bond lengths in appropriate molecules.