Paul Walden

Paul Walden (; ; ; 26 July 1863 – 22 January 1957) was a Russian, Latvian and German chemist known for his work in stereochemistry and history of chemistry. In particular, he discovered Walden's rule, he invented the stereochemical reaction known as Walden inversion and synthesized the first room-temperature ionic liquid, ethylammonium nitrate. Provided by Wikipedia