A carbenium ion is a carbocation of the trivalent and classical type R3C+. It is one of two types of carbocation, the other being a carbonium ion. In older literature a carbocation of the type R3C+ may still be referred to as a carbonium ion, a term that is used now for five-coordinate carbon atoms. [1] The current definitions were proposed by the chemist George Andrew Olah in 1972. [2] and are now widely accepted