Hydroxide-ion binding to nonionic interfaces in aqueous solution

Abstract

The mechanism of hydroxide ion binding to nonionic surfaces is explored by variation of the properties of the water-aggregate interface and by variation of the type of the aggregate.

Hydroxide and hydronium ion adsorption — A survey

“…Numerous experimental studies have revealed that inert surfaces show a negative surface charge in neutral solutions and isoelectric points (IEP) close to pH 4. Similar characteristics were observed in experiments with oil/water [10][11][12][13][14] and gas/water [15][16][17][18][19][20] interfaces.…”

“…Although the majority of integral experiments suggest a preferential adsorption of hydroxide ions [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], an opposite picture has emerged from experiments analyzing molecular structures and MD simulations [21•-26]. These studies concluded that the concentration of hydronium ions, but not hydroxide ions, is enhanced at the gas/water interface [21•-26].…”

Self‐Assembled Nanoreactors

“…For that reason, the Kemp elimination (Scheme 7) was studied in the presence of aggregates formed by a series of surfactants. [157][158][159] With respect to the reaction in pure water at the same pH, the elimination rate was increased up to 850 times. It turned out that vesicles were more effective catalysts than micelles, likely providing a more apolar microenvironment at the substrate binding sites for the deprotonation of the substrate.…”

“…158 The introduction of various other additives, such as linear alcohols and alkyl pyroanosides, led to changes in the vesicular catalysis reflecting its dependence on the molecular properties of the interface between the vesicle and bulk water. 159 The results obtained by the Engberts' group indicate that a highly complex mix of factors is involved in catalytic reactions occurring in synthetic and probably also in biological cell membranes. One of these factors is the counterion, which not only acts as a charge compensator but also can function as an active catalyst as already exemplified in the case of micelles (vide infra).…”

Vesicular catalysis of the decarboxylation of 6‐nitrobenzisoxazole‐3‐carboxylate. The effects of sugars, long‐tailed sugars, cholesterol and alcohol additives

“…The trends in the T m of vesicles formed from DHAB and additives used in this study are similar to those found for mixed vesicles formed from dimethyl-di-n-octadecylammonium chloride and organic additives. 29 However, upon addition of small amounts (<30 mol.%) of all additives a slight decrease in T m was found. Above 30 mol.%, C 12 Mal and C 12 Glu both give a further decrease in the main phase transition temperature upon increasing the mole fraction of additive.…”