Pyridinium bromide quaternary

Avigad and Milner224 used a turbidimetric method based on the measurement of residual turbidity caused by complexing the acid polysaccharide with such quaternary ammonium detergents as cetyl-pyridinium bromide. The activity unit was expressed as the amount of enzyme bringing about a decrease of absorbance at 400 nm of 0.01/min. 

On the other hand, cationic polymer brushes grafted on PET surfaces could prevent microbial infection in industrial and medical fields, such as alkyl pyridinium or quaternary ammonium moieties. Gen et al. grafted copolymerized with 4-vinylpyridine (4VP) and subsequently quaternized with hexylbromide [53,54], and N-hexyl-N -(4-vinylbenzyl)-4,4 -bipyridinium bromide chloride (HVV) [55] onto PET films for enhancing antibacterial properties. The PET films were pretreated by argon plasma to form surface... 

Of derivatives of compound 3, the zwitterions 245 react with DMAD if magnesium bromide is added to give aminopyridine derivatives (00H(53)265). Compounds such as 102 are opened by acid to give quaternary pyridinium salts (92LA885). There are various interconversions of 2-substituted triazolopyridin-3-ones into 1-substituted zwitterions. An example is the reaction of 246 (83BCSJ2969) the reverse conversion is also reported. 

Fig. 10.8 A where the R substituents are alkyl or heterocyclic radicals to give compounds such as cetyltrimethylammonium bromide (cetrimide), cetylpyridinium chloride and benzalkonium chloride. Inspection of the stmctures of these compounds (Fig. 10.8B) indicates the requirement for good antimicrobial activily of having a chain length in the range Cg to Cig in at least one of the R substituents. In the pyridinium compounds (Fig. 10.8C) three of the four covalent links may be satisfied by the nitrogen in a pyridine ring. Polymeric quaternary ammonium salts such as polyquatemium 1 are finding increasing use as preservatives.

In the presence of 15% pentanol, large amounts of water can be solubilized into heptane or toluene solutions of Ci2-Ci6 alkylpyridinium or alkyltrimethylammo-nium bromides (Venable, 1985). In heptane/pentanol, the longer-chain surfactants appear to be more effective than the shorter ones, while in toluene/pentanol the shorter ones appear to be more effective. In both solvent mixtures, the pyridinium salts are more effective solubilizers than the corresponding trimethylammonium salts. All the quaternaries investigated were more effective than sodium dodecyl sulfate. 

Quaternary pyridinium polymers can show biological activity when bound to surfaces, e.g., poly(4-vinyl pyridine)-modified glass surfaces which were modified using different alkyl bromide derivatives. Suitable polymers for antibacterial applications not only exhibit antibacterial activity, but also non-toxicity to human cells (i.e., selectivity). 

The synthesis of pentazocine is comparatively short. The Grignard reaction with a pyridinium salt is followed by partial hydrogenation. Cleavage of the methyl ether is accompanied by acid-catalysed alkylation, which leads to the buildup of the quaternary centre. Finally, the amino-function is demethylated with cyanogen bromide and alkylated with isopentenyl bromide. 

These residues from cleaning agents and other fluids containing surfactants (e.g., cetyl pyridinium chloride and cetyl trimethyl ammonium bromide) may have bacteriostatic effects or cause flavor taints. To determine quaternary ammonium compounds (QACs), they are first extracted into solvent (1,1,2,2-tetrachlor-ethane) and then detected by the formation of a pink color with dioctyl sodium sulfosuccinate (Aerosol T), which is quantified by spectrophotometry. 

Tanaka and his associates demonstrated for the first time how to use non-volatile ionic liquids (ILs) as solvents in palladium-catalyzed carbonylations [163], In the case of alkoxycarbonylation of bromobenzene, higher yields were obtained when 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] was used as the reaction medium compared with standard conditions. And the selectivity for the monocarb-onylation of iodobenzene with t -PrOH or Et2NH was significantly enhanced by [bmim][BF4]. After separation of the products, the solvent-catalyst system was easily recycled and exhibited catalytic activity up to seven times. Since then the replacement of traditional solvents with quaternary ammonium halides, imidazoli-um- or pyridinium-derived ILs has gained increasing importance [164—173]. Recently, the phosphonium salt IL trihexyl(tetradecyl)phosphonium bromide has proven to be an effective reaction medium for various carbonylation reactions of aryl and vinyl bromides or iodides under mild conditions (Scheme 2.17) [174]. 

The pyridinium moiety may also be utilized in the construction of cationic receptors. For example, Shinoda et al. have reported the quaternary tetrapyridinium macrocycle 73 which may be prepared directly from an aqueous solution of bromomethylpyridinium bromide (Figure 40). This solution was neutralized with sodium bicarbonate and the bromomethylpyridinium bromide extracted into DCM. When the solvent was removed from the organic layer at room temperature, N-aUcylation occurred, giving a mixture of quaternary pyridinium salts. Crystalline 73 2H2O was obtained in 2% yield by recrystallization from water. 

Quaternary derivatives of 2- and 4 halogenopyridines are readily hydrolysed. Thus, alkali converts 2-chloro-l-phenacylpyridinium bromide into l-phenacylpyrid-2-one 4 , and other examples are known 28, 33ia, 949, Acid hydrolysis also occurs 28 that of l-ethyl-2-iodo-3- and -5-methylpyridinium iodides is accompanied by the formation of iodinated products 28, 4-Halo-geno-l-(4 -pyridyl)pyridinium chlorides give l-(4 -pyridyl)pyrid-4-one i7. 

The nitro group in quaternary salts of 4-nitropyridine is easily replaced. Recrystallization of the methiodide from undried acetone gives l-methyl-4-pyridone . Reaction of 4-nitropyridine with benzyl chloride yields 1-benzyl-4-pyridone, and with benzyl bromide, l-benzyl-3,5-dibromo-4-pyridone (nuclear bromination is thought to result from the oxidation of hydrobromic acid by nitrous acid) the experimental description suggests that in these reactions nucleophilic replacement of nitro by halide may occur initially . The consequences of the autoquaternization of 4-nitropyridine have already been mentioned. The formation of 4-hydroxypyridine from 4-nitropyridine and acetic anhydride a presumably involves the acetyl-pyridinium salt. 4-Nitropyridine 1-oxides give with acetic anhydride mainly 4-hydroxy-or 4-acetoxy-3-nitropyridine l-oxides sic but the presence... 

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