Ammonium-centered cationic

Zwitterionic micelles of the sulfobetaine C16H33N+Me2(CH2)3SO 3 have effects very similar to those of cationic micelles (Table 7). This result is understandable if the substrate binds close to the quaternary ammonium center and the anionic sulfate moiety extends into the aqueous region. 

The sulfonate moiety is only weakly nucleophilic in water, and the effects of micellized SB3-16 upon hydrolyses are generally very similar to those of cationic micelles (Tables IV-VI). This behavior suggests that in both systems the substrates bind close to the quaternary ammonium centers and that the sulfonate moiety, like a micellar-bound counteranion, is in the water and therefore not interacting strongly with the substrate (65). The only exceptions to this generalization were observed with hydrolyses of some acid chlorides (Table V). In these reactions, the balance between bond making and breaking seems to be very sensitive to the reaction medium (58). 

The n values were high for all of the ionic liquids investigated (0.97-1.28) when compared to molecular solvents. The n values result from measuring the ability of the solvent to induce a dipole in a variety of solute species, and they will incorporate the Coulombic interactions from the ions as well as dipole-dipole and polarizability effects. This explains the consistently high values for all of the salts in the studies. The values for quaternary ammonium salts are lower than those for the monoalkylammonium salts. This probably arises from the ability of the charge center on the cation to approach the solute more closely for the monoalkylammonium salts. The values for the imidazolium salts are lower still, probably reflecting the delocalization of the charge in the cation. 

This chapter describes our studies of electrophilic systems having adjacent, stable cationic centers. We have shown in a wide variety of systems that stable cationic centers (i.e., ammonium, pyridinium, and phosphonium groups) can enhance the reactivities of some electrophiles. This enhanced reactivity is evident by reactions with weak nucleophiles, but may also involve unusual rearrangements or regiochemistry in the conversions. Using this chemistry, reactive dicationic systems can be generated and studied. 

The protonation of the methyleneiminium cation gives rise to the superelectrophilic methyleniminium dication, 19, which is a gitonic 1,2-dicationic species (carbenium ammonium species). Such a carbodication has been observed by charge stripping mass spectrometry by Schwarz and coworkers.Olah and coworkers have shown by theoretical calculations that the carbenium ammonium species, 19a, is 27.6 kcal/mol more stable than the three-center two-electron (3c-2e) bonded structure, 19b. ... 

High surface area hexagonal mesoporous Ge also can be prepared with oxidative self-polymerization chemistry of [Ge9] clusters [48]. This synthetic route does not require external oxidants such as ferrocenium or linking Ge(lV) centers and occurs in the presence of cationic surfactant (iV-eicosane-A ,A -dimethyl-A -(2-hydroxyethyl)ammonium bromide, EDMHEABr) as stmcture-directing agent. The polymerization reaction proceeds through the slow oxidative coupling of (Ge9)-clusters and seems to be accompanied by a two-electron process (2). The electron acceptors in this case appear to be the surfactant molecules or the solvent. 

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