Quaternary Ammonium Compounds
Quaternary ammonium cations, also known as quaternary ammonium salts, quaternary ammonium compounds or "Quats", are salts of quaternary ammonium cations with an anion. Quats are positively charged ions of the structure NR4+ with R being alkyl groups. Unlike ammonium NH3 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.
The general formula of a quaternary ammonium compound (quat) is:
- FeF Chemicals manufactures quats using only high purity tertiary amines with various alkyl chain lengths, normally ranging from C12 to C18.
Quats' Mode of Action - Surfactants
The majority of applications for quaternary ammonium compounds (Quats) are related to their very strong affinity for surfaces, which makes them powerful surfactants. The quaternary ammonium compounds adsorb on almost any surface resulting in the formation of a monolayer. As most surfaces, including skin, mucosa and hair, are charged negatively, they attract the positively charged quaternary ammonium ions.
The quaternary ammonium compounds contain a hydrophobic group like for example the tetradecyl group in Tetradecyl Trimethyl Ammonium Bromide (Cetrimide) or the cetyl group in Cetyl Trimethyl Ammonium Bromide (CTAB). This group has an oily character and thus it repels water. When absorbed on surfaces this oily group extends outwards from the surface as illustrated below:
The formation of this monolayer of oil and the neutralization of surfaces, as well as their good wetting and adhesive properties, form the basis for the utilization of quaternary ammonium compounds (Quats) in many different fields of application.
The properties of the quaternary ammonium compounds (Quats) vary by:
- the number and length of the alkyl chains
- introduction of various active groups in the molecules
- selection of the corresponding anion (chloride, bromide, etc.)
In general quaternary ammonium compounds are incompatible with anionic surfactants, soaps and synthetic anionic detergents. They are however compatible with non-ionic as well as with amphoteric detergents. The anionic sarcosinates are claimed compatible with quaternary ammonium compounds. Formulation of conditioning shampoos, combined cleaners and disinfectants etc. based on quaternary ammonium compounds and sarcosinates or non-ionic detergents is a possibility.
