What is a quaternary ammonium ion and what significance does it have in relation to amines? Reactions?

Answer 1

A quaternary ammonium ion is formed when the N atom of an amine donates its lone pair of electrons to an electron deficient species. The resulting co-ordinate bond makes the N atom positively charged.

Quaternary ions arise as intemediates in many reactions such as the Hoffmann's elimination reaction.