Effect of Multiple Field Assistance with Reversed Micelles on the Decarboxylation of 6-Nitro-1,2-benzisoxazole-3-carboxylate

Abstract

Decarboxylation reaction of 6-nitro-1,2-benzisoxazole-3-carboxylate (1) in cationic and anionic reversed micelles has been investigated with particular attention to the microenvironmental effect, such as microviscosity, micropolarity, and microactivity, in the specific and restricted reaction field as provided by reversed micelles. In 0.20 M CTAC/0.32 M H2O/CHCl3 reversed micelles, the reaction was accelerated about 1300-fold compared with that in bulk aqueous solution. Of various surfactant aggregate systems such as aqueous micelle, bilayer, and reversed micelle, the cationic reversed micelle could provide the most effective reaction field for the present decarboxylation reaction. This reaction is never accelerated in an anionic aqueous micelle. However, in the anionic AOT reversed micelle, the reaction was apparently accelerated by both lowering the micropolarity and increasing the microviscosity around the substrate. The unique rate enhancement for the decarboxylation reaction of 1 provided by reversed micelles was interpreted in terms of the “multiple field assistance.”

Decarboxylation of 6-Nitrobenzisoxazole-3-carboxylate in Mixed Micelles of Zwitterionic and Positively Charged Surfactants

“…Rates of NBOC decarboxylation have been determined in several microheterogeneous systems such as micelles, ,− reverse micelles, , vesicles, , polymers , and microemulsions . The effects of these microheterogeneous systems on k ψ have been related to micropolarity and surface potential of micelles, local ion concentration, surface hydration, and changes in aggregate structure …”

Buffer-like Action in Water Pool of Aerosol OT Reverse Micelles

“…The water microdroplets, often called “water pool”, formed in the central region of the reverse micelles provide a useful hydrophilic reaction field. The reaction field effects for the water pool on various photoreactions and thermal reactions and physical transitions have attracted considerable interest. − Knowledge of the water pool properties, e.g., local viscosity, − local polarity, ,− local acidity, − and their heterogeneous structure (distribution along the water pool radius direction), ,,, is required to fully understand the unique reaction systems in this hydrophilic nanospace.…”