Alkyl imidazolines and other heterocyclic cationics

Most unsaturated ring quats of industrial importance are alkylpyridinium halides (I) and substituted imidazolinium compounds (11). To prepare alkylpyridinium halide, pyridine is reacted with the equimolar amounts of alkyl halide for several hours at 100-150 °C without solvent according the reactions given above. The reaction is two orders slower in this case because the basicity of pyridine is much weaker in comparison with aliphatic tertiary amines and heterocyclic aliphatic amines, such as N-alkylpiperidine and N-alkylmorpholine, too. Typical examples of the aromatic quaternaries are given below  

Instead of alkyl halide, short-chain dialkylsulphate can be refluxed with imidazolinium to produce quaternary imidazolinium compound [52, 101,102a] such as shown below  

The surfactants in which the second long chain R is interrupted by the ester or amido group show better biodegradability. Alkylethylmorpholinium ethosulphate (e.g., Forestall cationic series, were alkyl = tallow or soy) is used as water-soluble conditioning agent compatible with some anionic surfactants. Other heterocyclic compounds have not so mueh practieal importance. The heterocyclic quaternaries are used as antistatics, fabric softeners, antimicrobial agents and corrosion inhibitors. 

Products of industrial importance are (I) alkylpyridinium halides known, e.g., as Dehyquart C/D of Henkel and Emcol E 607S of Witco, (II) Accosoft 808/808HT of Stepan, Ammonyx 4080 of Onyx, Rewoquat W75/W90 and Varisoft K-75/455/475/3690 series of Witco. 

Cationic non-nitrogeneous surfactants may be synthesized essentially in the same way as the nitrogeneous compounds. So, tertiary long-chain phosphines or arsines are quatemised with conventional alkylating agents, such as alkyl halides or alkyl sulphates [101, 102]. However, heterogeneous chain compounds other than N-containing ones are not so beneficial especially from an economical viewpoint. 

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