Alkylpyridinium halides

Figure 2, Surface tension of alkylpyridinium halides at 30°C. o Ci2PyCl A CmPyBr Cj gPyBr.

Pyridine is difficult to reduce (as is benzene ), but pyridinium salts, e.g. alkylpyridinium halides, are partly reduced by hydride transfer reagents such as lithium aluminium hydride (LiAlH ) and sodium borohydride (NaBH4). LiAlH, which must be used in anhydrous conditions, only gives the 1,2-dihydro derivative, but the less vigorous reductant NaBH in aqueous ethanol yields the 1,2,5,6-tetrahydro derivative (Scheme 2.30)1... 

Alkylpyridinium halides give mixtures of alkylpyridines on heating, e.g. (964) gives 2- and 4-picoline, with other minor products. This reaction is known as the Ladenburg rearrangement, and involves /V-alkyl bond homolysis. 

Because of the possibility of charge-transfer interactions between polar head and halide ion, ion specific interactions can be expected to be particularly marked for alkylpyridinium halides. From the CMCs counterion dependence3, as well as from counterion dissociation studies, binding is found to follow the sequence I- > Br > CP. The size of hexadecylpyridinium micelles is very sensitive to the anion of added salt, aggregation being promoted according to the sequence227 F [Pg.52]

Substituted indolizines 18 are formed in Chichibabin reactions of l-[alkyl(aryl)carbonylmethyl]-2-alkylpyridinium halides 17 (Scheme 11) <1972AJC1003>. Various modifications of this method are used for the preparation of many other pyrrolo[l,2-< ]azines and pyrrolo[l,2- ]azoles. Indolizines can also be made by intramolecular Michael additions, e.g., by the cyclization of 2-acylpyridine 19 (Scheme 12). 

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 ... 

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. 

In the past decade, ionic liquids have developed from a curiosity to a new class of solvent with attractive properties. However, the history of these salts goes back to the early twentieth century. In 1914, Walden reported that the [EtNH3][N03] salt 1 (Figure 2.1), with a melting point of 8 C, was liquid at room temperature. This interesting property did not attract a lot of interest until it was observed that mixtures of AICI3 and A-alkylpyridinium halide salt could be liquid at room temperature. 

Many conventional cationic surfactants have antibacterial properties, in particular the 1-alkylpyridinium halides and the benzaUconium chlorides (Af-benzyl-A Af-dimethyl-A-R chloride, R=Cg to C ). It is, therefore, only natural that ILBSs were tested for the same property, especially because this bears on their impact in the environment, for example, their toxicological effects on aqnatic organisms [73-76]. The emphasis in these stndies has been on the types of microorganism sensitive to ILBSs and the structme/activity relationships (SAR), in particnlar with regard to the length of the alkyl gronp, the heterocycle employed, and the counterion. 

Two relaxation processes were evidenced for a large number of surfactants by using two relaxation techniques or, in favorable instances, a single one. Examples of conventional surfactants sodium dodecylsulfate (shock tube (ST) or ultrasonic relaxation (USR) and p-jump - ) sodium tet-radecyl- and hexadecylsulfates (ST and p-jump ) alkylpy-ridinium sulfates (ST and p-jump ) alkylpyridinium halides (ST and p-jump ) alkylammonium halides (ST and p-jump ) surfactants with divalent counterions (T-jump, p-jump, SF ) two-chain surfactants (USR, SF, and p-jump ) nonionic surfactants (T-jump ). Examples of perfluoronated surfactants perfluorononanoate with various counterions (p-jump, T-jump, and SF ). Examples of dimeric surfactants the alkanediyl-a,co-bis(dodecyldimethylammonium bromide) (p-jump and ST °). 

Nakae, A., K. Kunihiro, G. Muto, Homologous alkylbenzyldimethylammonium chlorides and alkylpyridinium halides by HPLC,X Chromatogr., 1977,134,459-466. 

Ci2-C,8 alkyltrimethylammonium, C]2-C ji W-alkyl-V-benzyldi-methylammonium, and C12-C18 alkylpyridinium chlorides resolution of each type according to alkyl chain length C 2-C]8 alkyltrimethylammonium, C12-C18 Al-alkyl-lV-benzyldi-methylammonium, and C12-C18 alkylpyridinium halides resolution of each tj pe according to alkyl chain length C 6 alkyltrimethylammonium and Ci(i alkylpyridinium chlorides senaration from each other and... 

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