Acid Radical Quaternary Ammonium Salts


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Acid Radical Quaternary Ammonium Salts

Quaternary ammonium compounds (QACs) are active ingredients in over 200 disinfectants for use to inactivate virus. The amounts of these compounds used in household, workplace, and industry settings has very likely increased, and usage will continue to be elevated given the scope of the pandemic.

The general formula of quaternary ammonium compounds (QACs) is as follows:

General formula of QACFig 1. General formula of QAC

When X is an acid radical ion (HSO4-, SO42-, CH3COO-, PO43-, etc.), it is called acid radical quaternary ammonium salt.

A Synthesis Example of Acid Radical Quaternary Ammonium Salts

Menschutkin reaction is the most most common synthesis method of quaternary ammonium salt. Unfortunately, the most reactive alkylating agents in the Menschutkin reaction, namely iodides and bromides, result in the less desirable phase transfer catalysts. Consequently, an array of exchange reactions have been developed for the quantitative transformation of one ammonium salt into another. Frequently procedures have been reported for the synthesis of hydrogensulfates, chlorides, hydroxides, fluorides and carboxylates[1].

Here we mainly introduced the synthesis of TBAHS (tetrabutylammonium hydrogen sulfate).

More commonly known as TBAHS, tetrabutylammonium hydrogen sulfate is a stable and hygroscopic white solid which is widely used in various fields of chemistry as phase-trans-fer catalyst (PTC) and ion-pairing reagent as mobile phase additive in HPLC. It has been also used in a variety of organic transformations, some of which include the syntheses of triaryl pyridine, N-monosubstituted α-ketoamide, cyclic and acyclic β-disubstituted, α, β-unsaturated ketones, 1,8-dioxooctahydroxanthenes, etc.

Structure of tetrabutylammonium hydrogen sulfateFig 2. Structure of tetrabutylammonium hydrogen sulfate

TBAHS can be prepared from tetrabutylammonium azide by treating it with potassium hydrogen sulfate and 10% aqueous sulfuric acid in aqueous medium or from tetrabutylammonium thiocyanate by treating it with relatively concentrated sulfuric acid.

Synthesis of tetrabutylammonium hydrogen sulfateFig 3. Synthesis of tetrabutylammonium hydrogen sulfate

Alfa Chemistry offers various of acid radical quaternary ammonium salts including HSO4- series, SO42- series, CH3COO- series, PO43- series, HPO42- series, H2PO4- series, etc. 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. Sasson Y., Neumann R. (eds) Handbook of Phase Transfer Catalysis[M]. Springer, Dordrecht.