Non-ionic micelles

There are cationic, anionic, and non-ionic micelles. Divalent metal ions having positive charges are highly hydrophilic and cannot be incorporated into cationic micelles. Anionic micelles tend to form water insoluble salts with divalent metal ions. Interactions of non-ionic micelles with divalent metal ions appear to be small. Thus incorporation of a divalent metal ion into a micelle to form a catalytic center... 

Table 10 indicates the results obtained in non-ionic micelles and may be compared with Table 9 of cationic micelles. 

Micellar catalysis of decarboxylation of [52] was reported by Bunton and coworkers (Bunton and Minch, 1970 Bunton et al., 1971a Bunton et al., 1973). As illustrated in Table 5, cationic micelles, non-ionic micelles, and mixed... 

Non-ionic surfactants either decrease or have insignificant effects on the rate constants for hydrolysis of carboxylic esters (Lach and Pauh, 1959 Riegelman, 1960 Nogami et al., 1960, 1962 Kakemi et al., 1962 Mitchell, 1963 Behme et al., 1965 Mitchell and Broadhead, 1967 Saheki et al., 1968 Ullmann et al., 1968). The available data do not warrant conclusions on the relationship between substrate or surfactant structure on the magnitude or nature of catalysis by non-ionic micelles, but it should be noted that synthetic and naturally occurring amphiphiles cause very similar retardations of the rate of alkaline hydrolysis of ethyl p-aminobenzoate (Lach and Pauli, 1969). 

Tong et al. (1965) have investigated the effects of cationic, anionic, and non-ionic micelles on the hydroxide ion-catalyzed deamination of anionic indoaniline dyes, 23. The extent of partitioning, K, and the... 

The similarities between non-ionic micelles and globular proteins (Nemethy, 1967 Schott, 1968 Jencks, 1969) render micelles potentially useful as models for the investigation of hydrophobic interactions. Indeed, the stability of non-ionic micelles has been treated theoretically in terms of hydrophobic interactions (Poland and Scheraga, 1965). Since the critical micelle concentration is related to the degree and nature of the hydrophobic interactions of the amphiphile, its valne in the presence of additives and at different temperatures can be nsed as a quantitative measure of the effect of these variables on the hydrophobic interactions. In spite of the similarities between proteins and micelles, considerable caution is warranted in extrapolating the results obtained from micellar models to the more complex protein systems. 

Figure 7. Variations of aggregation numbers for ionic and non-ionic micelles in aqueous binary mixtures at 298.15 K...

C qTAB aggregates has little charge and that the kinetic data are similar to those found for non-ionic micelles. 

For example, reactions between anions and neutral molecules are typically speeded by cationic and inhibited by anionic, micelles, whereas reactions between cations and neutral molecules are typically speeded by anionic and inhibited by cationic, micelles. However charge effects are not all important, because reactions between non-ionic reactants are often speeded by micelles, and rates of some ionic reactions are affected by non-ionic micelles. Some examples of these rate effects are in Table 1 [1-6]. 

Hansen and Ugelstad [27,41] proposed that the radical capture efficiencies may not only be different for micelles and particles, but also among particles because of different sizes, surface charges, and monomer and radical concentrations. The rate of absorption of radicals in micelles and small particles may be lower than expected from diffusion-controlled irreversible absorption. Radicals arriving at the surface of the micelles can adsorb, thai desorb back into the bulk or diffuse further into the micelle. Because of the small size of the micelles, desorptirai can take place at a relatively fast rate. For ionic surfactants, the radicals approach the micelles, adsorb and desorb at almost equal rates, and essentially pass through the micelles. For non-ionic micelles, the presence of a condensed layer at the water side of the micelle can cause a higher resistance to radical capture and thus result in an even lower radical capture efficiency than for ionic miceUes. 

Scaling Theory of Non-ionic Block Copolymer Micelles 3.1 Spherical Non-ionic Micelles... 

Similarly to the case of non-ionic micelles, micelles with a charged corona can demonstrate shape transformations. The physical origin of these morphology... 

Surfactant-like zwitterionic hydroxamates show enhanced reactivities with 4-nitrophenyl acetate in cationic, zwitterionic, and non-ionic micelles compared with the non-micellar reaction. This is attributed to a hydrophobic ion pair and a lowering the pK of the hydroxamic acid. Similarly, sulphate transfer to surfactant zwitterionic hydroxamates occurs faster in the presence of cetyl-trimethylammonium bromide micelles than simple anionic hydroxamates." ... 

Dimerization of photoreactive olefins is generally enhanced in micelles. In iso-phorone (128) dimerization, the ratio of possible photodimers is altered on micellization, and acenaphthene dimerization to (129) gives 95% of product in non-ionic or anionic surfactant solution, but 10% on irradiation in benzene solution under otherwise identical conditions. The cis.trans ratio varies from 22.3 1 in sodium lauryl sulphate micelles, but 0.06 1 at low substrate concentration in non-ionic micelles. The crossed photodimer (130) is a significant product on co-irradiation of acenaphthene and acrylonitrile in micelles, but not in benzene. Irradiation of 3-alkylcyclopentenones in micelles of potassium dodecanoate gives 98% of head-to-head dimer (131), which is never the dominant product in organic solvents. This result implies ordering of the... 

The oxidation of dextrose by A -bromothalimide in H2SO4 both in the absence and in the presence of surfactants (sodium dodecylsulfate, tritonX-100) is fractional order in dextrose and negative fractional order in H+ the role of anionic and non-ionic micelle is best explained by Berezin s model. ... 

The effect of cetyltrimethylammonium bromide on the rate constants of hydrolysis of ethyl glycinate hydrochloride has been reported. " Cationic and non-ionic micelles inhibited and anionic micelles accelerated the acid hydrolysis of A-p-tolyl-benzohydroxamic acid (189). The rates of acid hydrolysis of acetohydroxamic acid, MeCONHOH, benzohydroxamic acid, PhCONHOH, and A-phenylbenzohydroxamic acid, PhCON(OH)Ph, were increased by perfiuorooctanoic acid and by sodium 1-dodecanesulfonate and sodium dodecyl sulfate (SDS). " The effects of micelles of SDS upon the rates of reaction of ionized phenyl salicylate with Bu"NH2, piperidine and pyrroiidine have been reported. 

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