Historical highlights in organoarsenic chemistry

Arsenic is a member of the nitrogen group of the Periodic Table, forming compounds in both the +III and +V oxidation states. Unlike some metals, arsenic also forms organometallic compounds in both oxidation states, R₃ As and R₅ As.^1,2 The R₃ As compounds are pseudo tetrahedral (like ammonia), and where three different organic groups are present, optical isomers of the type R¹ R² R³ As are known. Although generally synthetic, there are naturally occurring organoarsenic compounds. For example the arsenobetaine Me₃ As⁺ CH₂ CO₂ has been found in the tail of the western rock lobster³ and in the muscle and liver of the shark Prionace glaucus.⁴