Halide Quaternary Ammonium Salts


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Halide Quaternary Ammonium Salts

Quaternary ammonium compounds (QACs) were first introduced in 1917 and were probably the best known cationic surface-active agents. Their general formula is as follows:

General formula of QACFig 1. General formula of QAC

When X is a halide (F, Cl, Br, I), it is called halide quaternary ammonium salt.


The mainly synthesis way of halide quaternary ammonium salts is Menschutkin reaction[1] which converts a tertiary amine into a quaternary ammonium salt by reaction with an alkyl halide.

Halide quaternary ammonium salts were synthesized by reacting a tertiary amine with available alkyl halide. The reaction between a neutral amine and an alkyl halide producing two ions of opposite sign, also known as a Menschutkin reaction, is a bimolecular nucleophilic substitution (SN2) reaction.

This reaction occurs at an aliphatic carbon with a stable, electronegative leaving group (halide). The breaking of the carbon-halide bond and the formation of the new nitrogen-carbon bond occurs simultaneously during the transition state. In solutions, final products may exist as separate ions, ion pairs or solid salts[2].

Synthesis route diagram of halide quaternary ammonium saltFig 2. Synthesis route diagram of halide quaternary ammonium salt


Halide quaternary ammonium salts are the most common quaternary ammonium salts, and they can be used widely in sterilizing fields and industry fields. The mainly applications are showed below:

  • Fungicide

Halide quaternary ammonium salt can be used as fungicide like agricultural fungicide, public places fungicide, circulating water fungicide, aquaculture fungicide, medical fungicide, red tide fungicide, blue algae sterilizer and others. Especially, Gemini quaternary ammonium salt has outstanding bactericidal effect and low comprehensive cost.

Used as fungicidesFig 3. Used as fungicides

  • Antistatic softening agent

Halide quaternary ammonium salts can be used as antistatic softening agents in textile and printing and dyeing industry with excellent softness, antistatic, sterilization and anti-yellowing properties.

Used in textile and printing and dyeing industryFig 4. Used in textile and printing and dyeing industry

  • Flocculants and Demulsifiers

Halide quaternary ammonium salts are widely used in water treatment industry, as flocculant synergists. Because halide quaternary ammonium salts can cause suspended particles to stick together very strongly after coming into contact.

Used as flocculantFig 5. Used as flocculant

Halide quaternary ammonium salts are also used as demlsifiers. When it comes to separating crude oil and water, the halide quaternary ammonium salts work by either causing the oil droplets to clump together, massing the water droplets together, and by dropping the water.

Alfa Chemistry offers various of halide quaternary ammonium salts including fluoride Series, chloride Series, bromide Series and iodide Series. You can search the CAS No. or chemical name on our website. If you cannot find them, please feel free to contact us for custom synthesis.


  1. W. R. Brasen, C. R. Hauser (1954). "o-Methylethylbenzyl Alcohol". Org. Synth. 34: 58.
  2. Ugochukwu C. Okeke, Chad R. Snyder and Stanislav A. Frukhtbeyn. Synthesis, Purification and Characterization of Polymerizable Multifunctional Quaternary Ammonium Compounds[J]. Molecules, 2019, 24, 1464.