Russian-born U.S. chemist who was one of the first to investigate high-pressure catalytic reactions of hydrocarbons (hydrocarbon) and who developed a process for manufacturing high-octane gasoline.

In 1887 Ipatieff became an officer in the Imperial Russian Army and later attended the Mikhail Artillery Academy (1889–92), St. Petersburg, where he served as professor of chemistry (1898–1906). In 1897 he went to Munich to study and, while there, discovered the structure of isoprene, the basic molecular unit of rubber. Continuing his studies of hydrocarbons after his return to Russia, he soon learned to control and direct high-pressure catalytic reactions.

At the outbreak of World War I, Ipatieff was appointed chairman of the chemical committee of the Russian government, and throughout the war he served in administrative positions in the chemical industry. In spite of his anti-Communist feelings, he continued to work for the government after the Russian Revolution, but in 1930 he left the U.S.S.R. and accepted a position with the Universal Oil Products Company, Chicago. There he developed his catalytic processes for industrial use. Among the most important applications of these processes was the manufacture of high-octane gasoline from low-octane fuels.