Solubilization tendency of 1-alkanols and hydrophobic interaction in sodium lauryl sulfate in ordinary water, heavy water, and urea solutions

Abstract

6445dehydration may be required to account for this. The present study, as shown above, provides us some evidence to indicate the structure of acid sites included in silica-alumina and silica-coated alumina. First, we can conclude that the silica on alumina does not possess such acid sites as found in the silica-alumina catalyst. In other words, silanol attached to AI does not show strong Bransted acidity. This is in agreement with the conclusion by Kawakami et al. on the basis of the quantumchemical cal~ulations.~ They proposed a distorted structure consisting of silicon and aluminum for the strong Bransted acid sites. In the boundary layer between alumina and silica, the species as assumed or the substituted aluminum cation like in zeolite framework could be formed to play the role of the Bransted acid site.Because the electronegativity of the silicon cation (Si4+) is larger than that of the aluminum cation (AI3+), the silicon atom pulls an electron to become negatively charged; in place of that, the hydrogen of hydroxide becomes positively charged, Le., -A I U Si--OH+. Because of the induced effect, silanol attached to aluminum may behave as a weak Bransted acid site. It can be postulated that the distribution of the acid strength is fine due to the discrete structure of deposit silanol. Therefore, the silica monolayer on alumina could catalyze the appropriate reaction effectively. The sharp distribution of the acid site with a homogeneous strength of the acidity may be a characteristic of the material distinguishable from usual mixed oxides. ConclusionsI . Chemical vapor deposition of silicon methoxide on alumina formed the monolayer of silica fully covering the alumina surface. Further deposition of silica is possible; double-layer formation is suspected.2. The silica monolayer does not possess the strong Bransted acidity for the cumene cracking but does possess the weak acidity to catalyze the isomerization of butene and the dehydration of tert-butyl alcohol. The acidity may be created by an induced effect of the assumed species -A I U S i -O H , and a fine distribution of the acidity strength is estimated.The effects of I-propanol, 1-butanol, I-hexanol, and 1 -octanol on the micellization parameters of sodium lauryl sulfate (NaLS) in heavy water (D20) and in aqueous urea solutions, solvent systems with stronger and weaker hydrogen-bonded skeletal structures, respectively, than in ordinary water, have been determined at 25 OC. We have also determined the transfer free energy of an alcohol from H20 to D20 and also to urea solutions by head space gas chromatography. Results show the following: (1) The ability to depress the critical micelle concentration (cmc) increases in going from D20 to H20 to 5 M urea, the direction of decreasing structuredness of the solvent system. (2) The coaggregation equation ( J . Phys. Chem. 1983, 87, 5443), relating the ability to depress the cmc and the ability to increase the micellar degree of ionization to the distribution coefficient of the amphiphilic additive between the m...

Fluorescence of 8-Anilinonaphthalene-1-sulfonate and Properties of Sodium Dodecyl Sulfate Micelles in Water–Urea Mixtures

“…2b are given in Table 2. In the range of urea concentrations from 0 to 5 M, where comparison is possible, the values obtained here are in very good agreement with literature values derived from specific conductance measurements (5). A notable aspect of the results shown in Fig.…”

“…It has been found that urea (A) increases the criti-Similarly, urea was assumed to be a nonpenetrating agent cal micelle concentration of ionic (1, 4-7, 12, 15-17) and in a study performed by Gonzalez et al (12) on the effect nonionic (1,2,7,9) surfactants; (B) decreases the micellar of additives on the solubility of naphthalene derivatives in size of ionic (8,14,17) and nonionic (9) surfactants; (C) micellar solutions. Alternatively, results from recent studies increases the counterion dissociation degree of ionic micelles have been interpreted in favor of a direct mechanism of urea (5,8,15,16); (D) increases the cloud point of nonionic action on properties of micelles (1-4, 13, 15, 17). Most of the studies concluding that urea acts according to the direct 1 To whom correspondence should be addressed.…”

“…Additives, particularly urea, can modify water or water plus urea mixtures were measured as follows. the micellar microenvironments but also alter the solubiliza-A dilute solution of ANS in water or water plus urea was tion behavior (5,12) and the photophysics of the probe in shaken with n-octanol for ca. 10 min.…”

Tl+/Na+Competitive Binding at the Surface of Dodecylsulfate Micelles in Water–Urea Mixtures

“…Miyaghisi et al (11) performed a study of proteins (15) and alters several properties of micellar of the alteration in properties of micelles induced by pertursolutions: (A) it increases the critical micelle concentration bation in the external environment and used urea as an addiof ionic (1,5,7,9) and nonionic (1,2,6,9) surfactants; tive assumed to be unable to penetrate the micelles. Simi-(B) it decreases the micellar size of ionic (8,14) and non-larly, urea was assumed to be a nonpenetrating agent in a ionic (6) surfactants; (C) it increases the counterion dissoci-study performed by Gonzalez et al (12) regarding the effect ation degree of ionic micelles (5,7,8); (D) it increases the of additives on the solubility of naphthalene derivatives in cloud point of nonionic (2,6) and decreases the cloud point micellar solutions. Alternatively, results from recent studies of zwitterionic (10) surfactants; (E) it increases the local have been interpreted to favor a direct mechanism of urea viscosity and decreases the local polarity at the micellar action upon properties of micelles.…”

The Impact of Surfactants on FeIII–TAML‐Catalyzed Oxidations by Peroxides: Accelerations, Decelerations, and Loss of Activity

“…[30] The reactivity of 1 strongly decreases on going from water to organic solvents, [39] which may be partly due to a decrease in the dielectric constant of the media, but alcohols are known to influence the dielectric constant within micelles, [38] as well as influencing other key properties. [43][44][45] …”