Cationic surfactants are being used in various applications industrially and domestically for a long time. Pyridinium salts come under the category of cationic surfactants. These are unsaturated heterocyclic compounds having different functional groups present either on pyridine ring or at nitrogen atom. Initially, they were only considered as effective germicides. Several researches have been done for the modification of the properties of these salts, making them important for various applications. This paper reviews the types, synthesis, properties, and applications of quaternary pyridinium salts.

4-Amino-decylpyridinium bromide (ADPBr), an antimicrobial surface active agent, was synthesized by quaternization of 4-aminopyridine (AP) with decyl bromide (DBr). The reaction was carried out at 1:1.2 molar ratio of reactants (4-aminopyridine and decyl bromide, respectively) at 200°C for 10 min. The maximum yield of the product was 74.6%. The structure of the synthesized product was characterized by using modern analytical techniques, such as FT-IR, 1 H NMR, and 13 C NMR. The antimicrobial activity of the salt was evaluated with minimum inhibition concentration method and showed good activity against gram-negative bacteria. The MIC of the salt was found to be 600 ppm for 2 × 104 CFU/mL of E. coli.