Quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure NR4+ with R being alkyl groups. Unlike the ammonium ion NH4+ itself and primary, secondary, or tertiary ammonium cations, the quaternary ammonium cations are permanently charged, independent of the pH of their solution. Quaternary ammonium cations are synthesized by complete alkylation of ammonia or other amines. For possible synthesis route, see amines.
Quaternary ammonium salts or quaternary ammonium compounds are salts of quaternary ammonium cations with an anion. They are used as disinfectants, as surfactants, as anti-electrostatics (e.g. in shampoo), and as phase transfer catalysts .
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