GRUENSTEIN, NATHAN (1877–1932?), German organic chemist. Gruenstein was born in Lithuania. Working for a chemical firm in Frankfurt on the Main, he developed a method of converting acetylene into acetaldehyde, with mercury salts as a catalyst, and thence into acetic acid, acetic anhydride, acetone, etc. His process, first used industrially in 1916, remained the chief method of producing these chemicals for nearly 50 years. Gruenstein was an active Zionist.