Quaternary compound
![Quaternary ammonium cation. The R's may be the same or different groups. They may also be connected (cyclic).](/Images/godic/202502/05/Quaternary_ammonium_cation.svg4324.png")
In chemistry, a quaternary compound is a cation consisting of a central positively charged nitrogen atom with four substituents, especially organic (alkyl and aryl) groups, discounting hydrogen atoms.
The best known quaternary compounds are quaternary ammonium salts, having a nitrogen atom at the centre. For example, in the following reaction, the nitrogen atom is said to be quaternized as it has gone from 3 to 4 substituents: