Cyclizations of 2-(ω-Bromoalkyloxy)phenoxide Ions in Dicationic Surfactants

Abstract

Cyclization of 2-(3-bromopropyloxy)phenoxide ion (PhBr7) in micelles is a model for SN2 reactions of nucleophilic anions at micelle-water interfaces. In this paper we report observed rate constants (kobs) in aqueous micelles of dimeric surfactants. kobs in 1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide ( 1) is constant in a range of concentration, then increases at high [1], suggesting a transition to a different type of aggregate. A 1 H NMR investigation confirms a phase transition at the [1] which corresponds to the reactivity change. (2S,3S)-2,3-Dimethoxy-1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide (2) forms very large aggregates and shows a modest catalytic effect. Cyclization of 2-(12-bromododecyloxy)phenoxide ion (PhBr16) in 1 under preparative conditions yields the intramolecular cyclic product only despite a low effective molarity and a relative high substrate concentration. This result reveals the presence of a well-organized substrate-surfactant aggregate.

A 1H NMR study of 1,4-bis(N-hexadecyl-N, N-dimethylammonium)butane dibromide/sodium anthranilate system: spherical to rod-shaped transition

“…The main features and peaks were similar as reported previously [34]. The cmc values determined from conductivity (2.0×10 −5  M, 25°C) and surface tension (2.63×10 −5  M, 35°C) measurements were in close agreement with the literature value [34–36]. All solutions for the cmc determination were prepared in demineralized double distilled water.…”

Influence of ionic and nonionic hydrotropes on micellar behavior of a cationic gemini surfactant butanediyl-1,4-bis(dimethylcetylammonium bromide)

“…Our results show that the cmc of pure surfactant agrees well with the literature [25][26][27] values (Fig. 1).…”

Synthesis and properties of ionic liquid-type Gemini imidazolium surfactants

“…Besides, compared with conventional surfactants, the ionic liquid-type Gemini surfactants show several advantages due to the existence of imidazolium head groups. For example, as cationic micelle systems, they would display a significantly stronger tendency toward self-aggregation, owing to the distinct polarizability of imidazolium head groups, and thus they could be used as supramolecular templates in the preparation of functional materials [11][12][13]; or may be applied to modify various types of chemical reactions: nucleophilic substitutions [14], decarboxylations [15], and cyclizations [16,17]. As the cationic reverse-micelle systems, they would show several advantages, such as the reverse micelles with big imidazolium head groups showing higher ca-* Corresponding author.…”