Solvent/substrate effects on the micelle-catalyzed aquation reactions of some iron(II) phenanthroline complexes, I. Influence of water and acid on the aquation of Fe(Ph2Phen)32+ in acetone

The effects of a substrate additive, H⁺ and solvents (water and acetone), on the micelle-catalyzed aquation of tris-(4,7-diphenyl-1, 10-phenanthroline)iron(II), Fe(Ph₂Phen)₃ ²⁺, have been investigated using^#Triton X-100 micelles. The k₀ vs. [TX-100] profiles at fixed [H₂O] are structured, exhibiting maxima. Catalytic factors of 46.6–171.7 are observed for 5.56×10⁻²≤[H₂O] 55.60×10⁻² mol dm⁻³. On the other hand, at fixed [H⁺], the k₀ vs. [TX-100] exhibit broad maxima. The aquation reaction is inhibited by H⁺ and catalytic factors decrease rapidly and exponentially from 422.5 to 20.9 for 0.20×10⁻³≤[H⁺]≤2.00×10⁻³ mol dm⁻³. The aquation is found to be faster (ca. 160–1200 fold) in acetone than in the aqueous medium depending on the added [H₂O]. These observations are rationalized on the basis of a proposed modified lamellar structure for the Triton X-100 (TX-100) micelles in which direct substitution of water molecules into the coordination sphere of the complex occurs.     

Alkaline hydrolysis of brilliant green in mixed cationic surfactant systems

Kinetic measurements were performed for the alkaline hydrolysis of brilliant green — a triphenylmethane dye used as a model compound for probing micellar rate effects. This reaction was studied both in the presence of tetradecyltrimethylammonium bromide (TTAB) and tetradecyltriphenylphosphonium bromide (TTPPBr) and also in binary mixtures of these surfactants at different mole fractions of each. All rate surfactant profiles were analyzed using the pseudo-phase model in order to obtain the regression parameters, including binding constants and rate constants in the micellar pseudo-phase. The reaction was catalyzed by both surfactants. The catalytic factor increases from about 10 for pure TTPPBr to about 38 for pure TTAB. Binding of BG to micellar surface is greater in pure TTAB than in pure TTPPBr but significantly reduced in the surfactant mixtures than in pure components. Reduction of the binding constant becomes more significant as the mole fraction of TTAB is increased in the mixture. The kinetic data have been analyzed in terms of models of Piszkiewicz and Raghavan-Srinivasan which are in good agreement.      

Salt effect on base hydrolysis of tris(1, 10-phenanthroline) iron(II) at 25°C

The kinetics of base hydrolysis of tris(1,10-phenanthroline) iron(II) has been investigated in the presence of sodium sulfate and sodium benzoate at 25°C. Pre-c.m.c. association constant (k_m) decreases as the salt concentration increases. The average number of monomer per micelle varies from 4 to 2.     

A kinetic model for the SDS micelle catalyzed hydrolysis of tris (3, 4, 7, 8-tetramethyl-1, 10-phenanthroline) iron(II) in alkaline medium

A kinetic model of micellar catalysis of more general application is proposed. Kinetic data in the base hydrolysis of Fe (Me₄phen) ₃ ²⁺ caalyzed by SDS micelle is adequately explained by the model.     

Periodate oxidation of dicyano-bis-(1, 10-phenanthroline) iron(II) dihydrate in aqueous sodium dodecyl sulphate (SDS)

Periodate oxidation of bis-(1,10-phenanthroline)-dicyano iron(II) ([Fe(C₁₂H₈N₂)(CN)₂]), known also as ferrocyphen, in SDS surfactant was studied in aqueous and acidic medium. The redox reaction is catalysed 124-fold in 1.220 × 10⁻⁴ mol dm⁻³ H₂SO₄ acid. The catalytic factor is much lower in absence of acid. The higher rates in acid-micelle solution are the reverse to what is observed in surfactant-free medium where acid inhibits the reaction. The results are interpreted in terms of electrostatic attraction between the protonated species and the anionic surfactant aggregates.     

Influence of the preparation conditions on the textural properties andn-hexane isomerization activity of Pt/SO42??ZrO2

The effect of Na₂SO₄ and PhCOONa on the aquation of [Fe(Me₄phen)₃]²⁺ has been investigated in pure Triton X-100 as solvent. The rate and mechanism of the aquation are explained in terms of changes in the mobility, activity and structure of H₂O in the restricted environment of water pockets in the Triton X-100 solvent.     

Mixed Micelles of Tetradecyltrimethylammonium and n-Alkyltriphenylphosphonium Bromides

The critical micelle concentrations (CMC) of binary mixtures of tetradecyltrimethylammonium bromide and n-alkyltriphenylphosphonium bromide (ATPPB) with alkyl chain length of 10, 12, 14, and 16 have been determined in water by conductivity measurements. The CMCs were lower than predicted from ideal mixing theory indicating positive synergistic interactions in mixed micelle formation. The results of the mixed systems were analyzed using the regular solution theory which allowed for the determination of the composition of the mixed micelle, the activity coefficients, and the pair-wise molecular interaction parameter β. The average β values were all negative showing significant deviation from ideality which increases as the chain length of the n-ATPPB increases. The excess free energy of the mixed systems was also calculated, and the values were all negative for the four mixed systems studied, an indication that the mixed micelles are thermodynamically stable relative to the individual component.