설명(영) |
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Quaternary Ammonium Compounds (generally referred to as quats) are positively charged tetra-substituted nitrogen derivatives of the following structure:
in which R, R', R'', and R''' may be the same or different, but may not be hydrogen; and in which X- represents a typical anion, e.g., chloride or methosulfate. If any or some of the R groups are hydrogen, the compounds of the above structures are amine salts (see Organic Salts) or amphoterics (see Alkylamido Alkylamines, Alkyl Substituted Amino Acids). The R groups may be aliphatic and carry additional substituents. The nitrogen atom may be part of a heterocyclic or aromatic ring system as (e.g., Cetethyl Morpholinium Ethosulfate or Steapyrium Chloride).
The quaternary nitrogen atom in these compounds always carries a cationic charge regardless of the pH of the system. At high pHs, the anion may be OH-, which may reduce the normally high water solubility of quaternary ammonium compounds.
The positive charge on the quats makes them substantive to the slightly negatively charged skin and hair proteins. This accounts for the use of most monomeric and polymeric quats for all types of hair and skin conditioning purposes and as antistatics. Some of the polymeric quats find use as hair setting and styling products. In addition, many quats have the ability to disrupt the surface membranes of microbial species and are widely used as antimicrobial agents (e.g., Cetyl Pyridinium Chloride or Benzalkonium Chloride). |