Amphiphilic compound carboxylic acid

These results are quite compatible with the preferred conformations of the two-chain carbonyl diacids in aqueous media mentioned above (Porter et al, 1986b, 1988). The meso-compounds preferred collinear conformation, which places the hydrogens at the asymmetric carbons in a nearly eclipsed position relative to each other (Fig. 44), is more stable than that of the ( )-diastereomer by about 1.2kcalmol 1. In this conformation, the two carboxylic acid groups at the ends of the chain can be attached to the water surface side-by-side. The entire molecule can then behave as a good-amphiphile whose structure is similar to a pair of single-chain fatty acid molecules bound side-by-side, each chain mirroring the other about the molecules plane of symmetry. 

Molecular recognition processes between amphiphilic biaryl dendrimers 2 (with carboxylic acid moieties) as host compounds and the protein chymotryp-sin as guest were compared with those involving corresponding benzyl ether dendrons 1 (Fig. 4.26) [44]. In the biaryl dendrimers both the carboxylic acid groups of the periphery and those located in the inner shells are available for... 

The molecular structure of retinoic acid is typical for an amphiphilic compound that is concentrated at interfaces. Further, the carboxylic acid groups allow such compounds to adjust their amphiphilic character by the degree of their dissociation. Surface tension measurements were carried out in order to determine the surface activity of retinoic acid [179]. The surface tension with respect to the concentration at pH 5 decreases more strongly than at pH 9. This reflects the fact that the protonated form of retinoic acid is more efficient in its surface activity than the deprotonated form. The critical micelle concentrations are 3.7 0.5 mg/L (pH 5) and 19 2 mg/L (pH 9). The limiting surface tension values in both curves is about 35 mN/m. Due to the precipitation of retinoic acid, the highest concentration in the surface tension curve at a pH of 5 was 20 mg/L. By contrast the solubility at pH 9 is at least 1 g/L. In order to verify the results from the FTIR measurements, films of the complexes were immersed in a solution of 0.15 mol/L sodium... 

Amphiphilic compounds — Compounds that possess both a hydrophilic and a hydrophobic part. Examples are carbonic acids, having a hydrophobic alkyl chain and a hydrophilic carboxyl group, lecithins, lipids, and many other organic compounds. See also -> hydrophilicity, and -> hydrophobic effect. 

Nonionic surfactants are amphiphilic compounds the lyophilic (in particular hydrophilic) part of which does not dissociate into ions and hence has no charge. However, there are nonionics, for example such as tertiary amine oxides, which are able to acquire a charge depending on the pH value. Even polyethers, such as polyethylene oxides, are protonated under acidic conditions and exist in cationic form. Long-chain carboxylic acids are nonionic under neutral and acidic conditions whereas they are anionics under basic conditions. So, the more accurate definition is as follows nonionics are surfactants that have no charge in the predominant working range of pH. The main part of nonionics can be classified into alcohols, polyethers, esters, or their combinations. 

Steroid derivatives were also employed as natural compounds able to confer amphiphilic properties to chitosan. Several examples of grafting of 5p-cholanic acid [72-75] and cholesterol [76] onto 0-glycol-chitosan are reported in the literature (Fig. 5). For steroids, the strategy relies on the activation of the carboxylic acid by iV-hydrosuccinimide in order to favor the grafting efficiency on the primary amine of glycol chitosan, mediated by EDC. 

At least two of the recognized mechanisms for the formation of electrical double layers (Hunter, elal. 1981 Russel etal., 1989) are relevant to LB film depositions (1) ionization of carboxylic acid group and amphoteric acid groups on solid surfaces, and (2) differences between the affinities of two phases for ions or ionizable species. The latter mechanism includes the uneven distribution of anions and cations between two immiscible phases, the differential adsorption of ions from an electrolyte solution to a solid surface, and the differential solution of one ion over the other from a crystal lattice. Since the solid-liquid and the film-liquid interfaces are flat, large surfaces and since both have a large, solid-like concentration, the analysis that follows applies to both interfaces. For an interface conformed by a thin film of an amphiphilic compound with the hydrophilic end of the molecule in contact with the water subphase, the equilibrium of charges is based on pH and subphase concentration. The effect of pH is highlighted by the definition of the of the carboxylic acid ... 

Polyfluorinated compounds comprise hundreds of chemicals characterized by hydrophobic linear alkyl chains partially or fully fluorinated (as the perfluorinated compounds [PFCs]) and containing different functional groups. Polyfluorinated compounds include perfluoroalkyl sulfonamides (PFASAs), fluorotelomer alcohols (FTOHs), polyfluorinated alkyl phosphates (PFAPs), fluorotelomer unsaturated carboxylic acids (FTUCAs), perfluoroalkyl acids (PFAAs), and their salts. The most common PFAAs are perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFASs). In particular, PFASs contain one or more fluorinated alkyl chains bonded to a polar head, which at neutral pH can be charged (anionic, cationic, and amphiphilic surfactants) or noncharged (nonionic surfactants). 

Fatty acid salts and many polar derivatives of fatty acids are amphiphilic, possessing both hydrophobic and hydrophilic areas within the one molecule. These are surface-active compounds that form monolayers at water/air and water/surface interfaces and micelles in solution. Their surface-active properties are highly dependent on the nature of the polar head group and, to a lesser extent, on the length of the alkyl chain. Most oleochemical processes are modihcations of the carboxyl group to produce specihc surfactants. 

With the purpose of preparing chitosan-based amphiphilic copolymer with only natural and renewable compounds, the grafting of fatty acids was investigated by several research groups [64-67]. Generally, the grafting occurred by formation of an amide bond between the primary amine of chitosan and the terminal carboxylic... 

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