Highly Altered State of Proton Transport in Acid Pools in Charged Reverse Micelles

Abstract

Transport mechanisms of solvated protons of 1 M HCl acid pools, confined within reverse micelles (RMs) containing the negatively charged surfactant sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) or the positively charged cetyltrimethylammonium bromide (CTABr), are analyzed with reactive force field simulations to interpret dynamical signatures from TeraHertz absorption and dielectric relaxation spectroscopy. We find that the forward proton hopping events for NaAOT are further suppressed compared to a nonionic RM, while the Grotthuss mechanism ceases altogether for CTABr. We attribute the sluggish proton dynamics for both charged RMs as due to headgroup and counterion charges that expel hydronium and chloride ions from the interface and into the bulk interior, thereby increasing the pH of the acid pools relative to the nonionic RM. For charged NaAOT and CTABr RMs, the localization of hydronium near a counterion or conjugate base reduces the Eigen and Zundel configurations that enable forward hopping. Thus, localized oscillatory hopping dominates, an effect that is most extreme for CTABr in which the proton residence time increases dramatically such that even oscillatory hopping is slow.

Scalable Transition-Metal-Free Synthesis of Aryl Amines from Aryl Chlorides through X@RONa-Catalyzed Benzyne Formation

“…The X@RONa clusters seemed to be thermodynamically more favored than other types of sodium alkoxide aggregates. , Spontaneous generation of X@RONa was always observed as long as halide anions were present, suggesting that NaH would behave similarly, although the direct observation of cluster formation cored by solid NaH was prohibitively difficult. Single-crystal X-ray diffraction data revealed that such endohedral mixed aggregates resembled reverse micelles, , wherein 12 lipophilic alkyl side chains positioned themselves outwardly, while the ions were located inside the cage (Scheme c). Its all-around aliphatic exterior shell and interchangeable ionic interior could make a potential phase-transfer catalyst that can carry insoluble NaH into organic solvents.…”