10.1021/ja00846a035
The study investigates the impact of cationic micelles, specifically hexadecyltrimethylammonium bromide (CTABr), on the acidity of carbon acids and phenols, as well as the electronic and 'H nuclear magnetic resonance (NMR) spectral characteristics of nitro carbanions in micelles. The researchers found that CTABr micelles significantly enhance the acid dissociation of various carbon acids and phenols, with the effect being most pronounced for nitro carbanions. The study involved several chemicals, including 4-nitrophenylacetonitriles, 1-nitroindene, 4-nitrophenol, and 2,6-di-tert-butyl-4-nitrophenol, which were used to examine the changes in their acid dissociation constants (pKa values) in the presence of CTABr micelles. Additionally, the visible and 'H NMR spectra of these nitro carbanions were analyzed to understand the interactions between the carbanions and CTABr molecules. The results showed that CTABr micelles cause a red shift in the visible spectra of nitro carbanions and induce upfield shifts in the 'H NMR signals of the aromatic protons of the carbanions and the N+(CH3)3 protons of the surfactant, indicating tight interactions. The study concludes that the presence of CTABr micelles enhances the acidity of carbon acids and phenols by stabilizing the anionic form through tight association with the surfactant molecules, and the spectral changes observed are attributed to the unique interactions within the micelle environment rather than chemical reactions.