Quaternary compound

Quaternary ammonium cation. The Rs may be the same or different groups. (The Rs may also be connected, making a cyclic ion.)

In chemistry, a quaternary compound is a compound consisting of exactly four chemical elements.

In another use of the term in organic chemistry, a quaternary compound is or has a cation consisting of a central positively charged 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:

R 3 N + R C l ⟶ R 4 N +   C l − {\displaystyle \mathrm {R_{3}N+RCl\longrightarrow R_{4}N^{+}\ Cl^{-}} }

Other examples include substituted phosphonium salts (R4P+), substituted arsonium salts (R4As+) like arsenobetaine, as well as some arsenic-containing superconductors. Substituted stibonium (R4Sb+) and bismuthonium salts (R4Bi+) have also been described.

See also


  1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: :(2006–) "Onium compounds". doi:10.1351/goldboo... ...read more
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