Scottish chemist who, independently of August Kekule, proposed the tetravalency of carbon and the ability of carbon atoms to bond with one another.

Couper was a student at the universities of Glasgow and Paris and became an assistant at the University of Edinburgh. Through Charles-Adolphe Wurtz, Couper submitted the paper on which his fame rests to the French Academy, but because Wurtz was not a member of the academy, the paper's presentation was delayed until June 14, 1858, about two months after Kekule's paper containing the same revolutionary theory had been presented. A controversy about priority ensued. Though Couper's paper was the first to use formulas picturing structural relationships of organic molecules by continuous or dotted lines, it was ignored. Kekule, by contrast, became famous. Couper had never enjoyed sound health, and after the rejection of his achievement he suffered physical and mental reverses and lived in retirement until his death.