The explicit consideration of ion exchange leads to a framework for the quantitative dissection and analysis of the influence of charged micelles on reactions which involve exchangeable ionic species. These include the following: (1) the binding of a reactive ion to the micelle in the presence or absence of salt and presence or absence of buffer; (2) the first-order reaction of an ionic substrate in the micelle; (3) the second-order reaction of an ionic nucleophile with a neutral substrate solubilized in the micellar phase; (4) the effect of micelles on the dissociation of weak acids; (5) the second-order reaction of the corresponding conjugate base. Model calculations based on the resulting mathematical expressions, which contain only experimentally accessible terms, are presented to exemplify the behavior patterns predicted by the model for each of these cases. These calculations illustrate the role that a given set of experimental conditions (unbuffered, buffered, added salt present, detergent concentration, etc.) plays in determining the concentration and kinetic behavior of exchangeable ionic reactants in the micellar pseudophase.

Product yields measured by high-performance liquid chromatography from chemical trapping of Cl -, Br -, and H2O by an aggregate-bound arenediazonium ion in cetyltrialkylammonium halide {(CTRA)X, R ) Me, Et, n-Pr, and n-Bu; X ) Cl, Br}, micelles are used to estimate, simultaneously, interfacial counterion, Xm, and water, H2Om, concentrations as a function of [(CTRA)X] and tetramethylammonium halide concentrations, [(TMA)X]. The results are interpreted by using a two-site pseudophase model. Values of Xm and H2Om are estimated by assuming that when the product yields from reaction of a long-tail aggregatebound arenediazonium ion in micelles are the same as the product yields from reaction of its short chain analogue in an aqueous quaternary ammonium ion salt solution, then Xm ) [Xw] and H2Om ) [H2Ow] in those solutions. The results show that Xm and H2Om are functions of headgroup size, surfactant concentration, and aqueous counterion concentration and type. Plots of Xm against [(CTRA)X] at a series of salt concentrations fall on separate curves. Xm increases gradually with added (CTRA)X and almost incrementally with added (TMA)X. However, plots of Xm and H2Om are essentially continuous functions of the aqueous counterion concentration, [Xw], at constant degree of micelle ionization, R. Three factors affect the shapes of these profiles. (a) An initial rapid increase in Xm is attributed to a salt-induced contraction of the micellar interfacial volume. (b) Above ca. 0.1 M [Xw], an incremental (slope of 1) increase in Xm with added counterion for (CTEA)Br, (CTPA)Br, and (CTBA)Br micelles is attributed to free movement counterions and co-ions between the interfacial region of the micelles (up to the micellar core) and the aqueous pseudophase. (c) Xm increases markedly for (CTMA)Br and (CTMA)Cl at their respective sphere-to-rod transitions ca. 0.1 M [Brw] and ca. 1.2 M [Clw]. The increases in Xm are accompanied by concomitant decreases in H2Om. Specific salt-induced rod formation is attributed to dehydration (partial) and tight ion pair formation between surfactant headgroups and counterions. Phase separation of (CTBA)Br micelles in 0.5 M (TMA)Br occurs when the interfacial water concentration is too low to maintain micelle stability. The dependence of Xm on [Xw] contradicts assumptions in the original pseudophase ion exchange model for aggregate effects on chemical reactivity that can be corrected, in part, by setting Xm equal to the sum the aqueous and interfacial counterion concentrations.

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Products from spontaneous reaction of a short-chain, water soluble arenediazonium salt, 2,4,6-trimethylbenzenediazonium tetrafluoroborate (1-ArN2BF4), in aqueous micellar solutions of cetyltrimethylammonium halides ((CTA)X (X = Cl, Br)) are used to estimate the degree of ionization, α, and the ion exchange constant, K Br/Cl. The arenediazonium ion (1-ArN2 +) reacts by rate-determining loss of N2 to give an aryl cation that traps available nucleophiles, i.e. H2O, Cl-, and Br-, to give stable phenol (1-ArOH) and halobenzene products (1-ArCl and 1-ArBr), respectively. Product yields are determined by HPLC from calibration curves obtained from independently prepared standards. Reproducible yields are obtained at very low halide ion concentrations, on the order of millimolar, well within the range needed to detect the “free counterions” in the aqueous intermicellar pseudophase. The basic assumption of the method is that 1-ArN2 + remains in the aqueous pseudophase at all (CTA)X and NaX concentrations. Trends in the Stern−Volmer constant for fluorescence quenching of Ru(bpy)3 2+ by 1-ArN2 + in (CTA)Cl/NaCl solutions strongly support this assumption. The results obtained by this method are in good agreement with literature values:  α = 0.25 and 0.29 for (CTA)Br and (CTA)Cl, respectively, and K Br/Cl = 2.65 ± 0.4. Potential applications of the method are briefly discussed.

We previously induced pathogenic antibodies against anionic phospholipids (PL) in experimental animals by immunization with lipid-free purified human beta2glycoprotein I (beta2GPI). We hypothesized that antiphospholipid antibodies (aPL) are induced by in vivo binding of foreign beta2GPI to self-PL, thus forming an immunogenic complex against which aPL antibodies are produced. If this hypothesis is true, other PL-binding proteins that are products of ubiquitous viral/bacterial agents may also induce aPL. To test this hypothesis, groups of NIH/Swiss mice were immunized with synthetic peptides of viral and bacterial origin that share structural similarity with the putative PL-binding region of beta2GPI. Compared with the control groups, animals immunized with the peptides produced significantly higher levels of aPL and anti-beta2GPI antibodies. These findings demonstrate that some PL-binding viral and bacterial proteins function like beta2GPI in inducing aPL and anti-beta2GPI production, and are consistent with a role for such viral and bacterial proteins in inducing aPL antibody production in humans.