Ingold, Christopher (Kelk) (1893–1970)

English organic chemist who specialized in the concepts, classification, and terminology of theoretical organic chemistry. He explained the mechanisms of organic reactions in terms of the behaviour of electrons in the molecules concerned. He was knighted in 1958.

Ingold was born in London and studied at Southampton. He became professor at Leeds in 1924, moving to University College, London, in 1930.

In 1926 Ingold put forward the concept of mesomerism, which allows a molecule to exist as a hybrid of a pair of equally possible structures. His ideas, first published in 1932, are still fundamental to understanding reaction mechanisms. They concerned the role of electrons in elimination and nucleophilic aliphatic substitution reactions, which he interpreted in terms of ionic organic species.

His Structure and Mechanisms in Organic Chemistry (1953) is a classic reference book.