1-Dodecyl-pyridinium

Fig. XI-13. Adsorption isotherms for SNBS (sodium p-3-nonylbenzene sulfonate) (pH 4.1) and DPC (dodecyl pyridinium chloride) (pH 8.0) on mtile at approximately the same surface potential and NaCl concentration of O.OlAf showing the four regimes of surfactant adsorption behavior, from Ref. 175. [Reprinted with permission from Luuk K. Koopal, Ellen M. Lee, and Marcel R. Bohmer, J. Colloid Interface Science, 170, 85-97 (1995). Copyright Academic Press.]...

The spectra of substituted pyridinium iodides are characterized by charge transfer bands involving the interaction of pyridinium and iodide ions. Mukerjee and Rayt showed that this band is shifted about 90 nm toward the red for dodecyl pyridinium iodide, which forms micelles, compared to methyl pyridinium iodide, which does not. They measured max for the micelles in mixed solvents of variable relative dielectric constant and obtained the following results ... 

Estimate the effective dielectric constant at the surface of the micelle from the fact that max occurs at 286 nm for dodecyl pyridinium iodide micelles in water. In light of the value estimated in Section 8.3 for the dielectric constant in the vicinity of solubilized benzene, does it seem likely that the value of er for bulk water applies in the Stern layer ... 

N-dodecyl pyridinium tetrakis (3,5-bis(trifluoromethyl)phenyl)borate... 

Szekeres, M., Dck any, I., and de Keizer, A., Adsorption of dodecyl pyridinium chloride on monodisperse porous sihca. Colloids Sutf. A, 141, 327, 1998. 

Spectral characteristics and selection of surfactant. Increase in the fluorescence intensity of the carbaryl solution was observed using SDS as surfactant at excitation and emission wavelengths of 281 nm and 349 nm respectively (Fig. 1). As can be seen from Fig. 1, Triton X-100 and dodecyl pyridinium chloride (DPC) decreased the fluorescence. This phenomenon clearly indicates that cationic surfactant (DPC) and neutral surfactant (Triton X-100) have negative effects on the fluorescence intensity for carbaryl while anionic surfactant (SDS) enhances the fluorescence intensity of carbaryl. This surfactant-enhanced phenomenon by SDS was used for the spectrofluorimetric determination of carbaryl. 

CMC) . In striking contrast, already in 1973, Muto and Meguro [66] had used several organic solvents like chloroform, benzene and cyclohexane on the one hand and the surfactants dodecyl pyridinium iodide and NaAOT on the other to examine the breaks in properties and determine the CMC s. The techniques included study of absorption spectra and light scattering. As expected, the values of the CMC were very small for most of the surfactant-solvent pairs and indeterminable for the polar molecule methanol. 

HOBS, dodecyl benzene sulfonic acid N-DPC, N-dodecyl pyridinium chloride. 

Strauss and Williamst have studied coil dimensions of derivatives of poly(4-vinylpyridine) by light-scattering and viscosity measurements. The derivatives studied were poly(pyridinium) ions quaternized y% with n-dodecyl groups and (1 - y)% with ethyl groups. Experimental coil dimensions extrapolated to 0 conditions and expressed relative to the length of a freely rotating repeat unit are presented here for the molecules in two different environments ... 

Decarboxylation is assisted by micellized pyridinium ion Aquation is accelerated by dodecyl-pyrazinium chloride... 

Thus, it was decided to employ a different substrate, and to that end we have followed the reaction of interphase-bound N-dodecyl 3-carbamoyl pyridinium bromide with cyanide ion at pH 11.8 (equation 1) in a cationic and in a nonionic microemulsion. 

N-dodecyl 3-carbamoyl pyridinium bromide (I) was prepared from vacuum-distilled n-dodecyl bromide (K K) and nicotinamide (Kodak) according to a published procedure (15) and identified... 

Kinetics. The reaction of N-dodecyl 3-carbamoyl pyridinium bromide (I) with cyanide ion in the microemulsions was observed by following the 340 nm absorption maximum of the 4-cyano adduct (II). See equation (1). Following the work of Bunton, Romsted and Thamavit in micelles ( ), a 5/1 mole ratio of KCN to NaOH was employed to prevent cyanide hydrolysis. The pH of each reaction mixture was measured on a Coleman 38A Extended Range pH meter to insure that the system was sufficiently basic to allow essentially complete ionization of the cyanide. The appropriate amounts of cyanide and hydroxide were added to the mlcroemulslon sample within 10 minutes of running a reaction. Cyanide concentration varied between 0.02 and 0.08 M with respect to the water content. Substrate was Injected via a Unimetrics model 1050 syringe directly into a known volume of the yE-nucleophlle mixture in a 1.0 cm UV quartz cell. Absorbance at 340 nm was followed as a function of time on a Perkln-Elmer model 320 spectrophotometer at 25.0 + 0.3 C. Since the Initial bulk concentration of substrate was 10 M, cvanide was always present in considerable excess. 

Table I. Phase volume corrected second order rate constants (k .) as a function of phase volume (( )) for the reaction of cyanide with N-dodecyl-3-carbamoyl-pyridinium ion in CTAB and BriJ 96 microemulsions...

ZnC12TPP+ — mejo-tris(4-Pyridyl)-iV-dodecyl-4-pyridinium)-porphyrinato-zinc(II)... 

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