150619-66-2Relevant academic research and scientific papers
Arenediazonium salts: New probes of the interfacial compositions of association colloids. 3.1,2 distributions of butanol, hexanol, and water in four-component cationic microemulsions
Yao, Jihu,Romsted, Laurence S.
, p. 11779 - 11786 (2007/10/02)
Product yields from dediazoniation of 4-hexadecyl-2,6-dimethylbenzenediazonium tetrafluoroborate, 16-ArN2BP4, bound to aggregates of four-component microemulsions composed of cetyltrimethylammonium bromide, (CTA)Br, H2O, hexadecane, and an alcohol, R'OH, either 1-butanol, BuOH, or 1-hexanol, HexOH, were used to estimate changes in H2O and R'OH compositions at the microemulsion interface over a range of microemulsion compositions. Analysis of % 16-ArOR'/% 16-ArOH product percent yield ratios obtained in the water-in-oil microemulsion region of the phase diagram at low water content show that mass action binding constants for the distributions of BuOH and HexOH between the interfacial and oil regions in these microemulsions are independent of [R'OH]. These results indicate that (CTA)Br mixes ideally with both alcohols and that alcohol binding is driven primarily by the hydrophobic effect with minimal contributions from specific interactions between R'OH and (CTA)-Br. We also show that our approach provides estimates of molar concentrations of BuOH and H2O in the oil. interfacial, and water regions at any composition of these 4-component microemulsions. Changes in the molar concentrations of H2O and BuOH mark the oil-in-water droplets to bicontinuous to water-in-oil droplets transitions. Potential applications of the dediazoniation method are discussed.
Arenediazonium salts: New probes of the interfacial compositions of association colloids. 2. Binding constants of butanol and hexanol in aqueous three-component cetyltrimethylammonium bromide microemulsions
Chaudhuri, Arabinda,Romsted, Laurence S.,Yao, Jihu
, p. 8362 - 8367 (2007/10/02)
Yields of aryl ether products, 16-ArOR′, were determined by HPLC with excellent reproducibility from dediazoniation of 4-hexadecyl-2,6-dimethylbenzenediazonium tetrafluoroborate (16-ArN2BF4) bound to surfactant aggregates in three-component microemulsions of cetyltrimethylammonium bromide ((CTA)Br), H2O, and an alcohol (R′OH), either 1-butanol (BuOH) or 1-hexanol (HexOH). The results were used to estimate the mole fractions (XA) of R′OH bound to the microemulsions, their mole fraction partition constants (KA), and mass action binding constants (KA′). Values of KA decrease with added R′OH consistent with literature results. Unexpectedly, values of AA′ are constant at all values of XA, indicating that (CTA)Br mixes ideally with both BuOH and HexOH in aqueous microemulsions and that binding of R′OH to (CTA)Br microemulsions is driven by a hydrophobic effect with minimal contributions from specific interactions between R′OH and (CTA)Br.
Arenediazonium salts: New probes of the interfacial compositions of association colloids. 1. Basic approach, methods, and illustrative applications
Chaudhuri, Arabinda,Loughlin, John A.,Romsted, Laurence S.,Yao, Jihu
, p. 8351 - 8361 (2007/10/02)
Product yields from the reactions of two different arenediazonium salts, z-ArN2+BF4-, bound to cetyltri-methylammonium halide ((CTA)X; X = Cl, Br) micelles and to aqueous three-component (CTA)X microemulsions containing an alcohol (R'′OH), either 1-butanol (BuOH) or 1 -hexanol (HexOH), are "snapshots" of the relative quantities of halide ion, water, and alcohol nucleophiles at the aggregates' interfaces. Yields of aryl ether, aryl halide, and phenol products measured simultaneously by HPLC are consistent with high concentrations of these nucleophiles in the immediate vicinity of the aggregates' interfaces. The interfacial concentration of each nucleophile is estimated from the yield of its respective product over wide ranges of (CTA)X and ROH concentrations by assuming that the selectivities of the long-chain (hexadecyl), water-insoluble, aggregate-bound arenediazonium ions, 16-ArN2+, toward anionic or neutral nucleophiles compared to water are the same as the selectivities of the short-chain (methyl), water-soluble analogues, 1-ArN2+, toward the same nucleophiles in aqueous solutions. The suitability of dediazoniation reactions as interfacial probes and the basic assumptions used in our approach are described. The observed rate constants for dediazoniation of the arenediazonium salts are almost completely independent of the salt, (CTA)X, and R′OH concentrations, consistent with rate-determining loss of N2 to give an aryl cation which reacts at diffusion-controlled rates with available nucleophiles. Salt-induced spectral shifts indicate formation of ion pairs in the ground state, and all our data are consistent with a heterolytic dediazoniation mechanism in which product distributions are determined by the equilibrium distribution of the ensemble of ground-state arenediazonium cation-anion and arenediazonium cation-molecule intimate pairs. Comparisons with previous results and potential applications are briefly discussed. The companion paper shows that ether product yields can also be used to estimate R′OH binding constants over a wide range of alcohol and surfactant concentrations.
