ABSTRACT
2-Naphthol (2NOH) was used as a fluorescent probe in order to examine and quantify the changes in hydrogen ion concentration in micelles formed by the zwitterionic 3-(tetradecyldimethylammonium)-propanesulfonate (SB3-14) surfactant or by anionic sodium dodecyl sulfate (SDS). In the presence of SDS, 2NOH is incorporated into the anionic micelle and the neutral form of the probe becomes the dominant species. The results are consistent with a microenvironment probably with a higher acidity and/or lower polarity in the micellar surface. The addition of SB3-14 generates a plateau at pH 3 to 9 with a fluorescent component of low intensity, which indicates the partial formation of 2NO(-)*, promoted by proton transfer to water. Theoretical results provided information on the structural parameters, emission wavelength, and changes in ΔpK(a) values due to the solvent, which are consistent with a solubilization site similar to aqueous ethanol. Zwitterionic surfactants concentrate anions such as trifluoroacetate in zwitterionic micelles, and as a result, the micellar surface charge becomes negative and promotes hydrogen ion incorporation into the micellar surface. Effects observed on the proton transfer between 2NOH* and anions in zwitterionic micellar solutions are complex and, besides the well-known anion incorporation, include changes in the surface potential and acidity of the surface. Zwitterionic micelles are able to emulate the mostly zwitterionic nature of biological membranes, and in the complex nature of zwitterionic micelles, we found reasons for the selection of zwitterionic headgroups in surfactants in natural systems as major components of biological interfaces.
ABSTRACT
Sucrose forms a dicationic complex with cobalt(III)bis(phenanthroline) which can be isolated as the sparingly water-soluble triiodide salt or the water-soluble chloride. The circular dichroism (CD) spectrum demonstrates the Delta configuration at Co(III) and the presence of two phenanthroline and one sucrose residues in the complex. The O-2(g)--O-1(f) distance in crystalline sucrose permits strain-free coordination of these centers with Co(III) and in the complex the H-1,1'(f) singlet of sucrose separates into a pair of doublets. The 1H NMR spectrum in DMSO-d(6) shows that OH-2(g) is deprotonated and the signal of OH-1(f) is shifted strongly downfield by complexation with Co(III). Coordination involving glucose and fructose residues is consistent with neither alpha-methyl glucoside nor fructofuranose forming mixed complexes with phenanthroline. Structure simulation with the semi-empirical PM3(tm) basis set indicates that complexation by O-2(g) and OH-1(f) can give a Delta-complex with little structural distortion, whereas in hypothetical Lambda-complexes there is distortion of the sucrose residue. Observation of an NOE involving the sucrose and phenanthroline residues supports the postulated structure of the Delta-complex.
Subject(s)
Organometallic Compounds/chemistry , Phenanthrolines/chemistry , Circular Dichroism , Cobalt/chemistry , Cobalt/metabolism , Fructose/metabolism , Glucose/metabolism , Ligands , Magnetic Resonance Spectroscopy , Molecular Structure , Sucrose/chemistry , Sucrose/metabolismABSTRACT
The delta-[Co(III)bis(phenanthroline)(sucrose)]3+ complex forms with little perturbation of the sucrose conformation, and complexation by HO-2(g) and HO-1(f).
Subject(s)
Cobalt/chemistry , Organometallic Compounds/chemistry , Phenanthrolines/chemistry , Sucrose/chemistry , Carbohydrate Conformation , Circular Dichroism , Cobalt/metabolism , Ligands , Models, Molecular , Molecular Structure , Organometallic Compounds/metabolism , Phenanthrolines/metabolism , Sucrose/metabolism , WaterABSTRACT
Anionic micelles of sodium lauryl sulfate, NaLS, catalyze the monoalkylation of Hg2+ in dilute acid by alkyl aquobis-(dimethyl glyoximato) cobalt (III), RCo(DH)2(H2O) degrees and the related propane derivatives RCo(DOH) DOpn (H2O)+, where R = Me, Et, n-C5H11. Nonionic micelles of Igepal do not catalyze the reaction. In the absence of micelles RCo(DH)2(H2O) degrees is considerably more reactive than RCo(DOH)DOpn(H2O)+, but this higher reactivity is offset in part by its higher basicity. Anionic micelles markedly increase the basicity of RCo(DOH)DOpn(H2O)+ and slightly increase that of RCo(DH)2(H2O) degrees. For reactions of the unprotonated Co(III) complexes the maximum rate enhancements by micelles of NaLS are: R = Me, 19(131); Et, 58 (65); n-C5H11, 46 (32). (The values in parentheses are for RCo(DOH)DOpn(H2O)+.)
Subject(s)
Cobalt , Colloids , Mercury , Micelles , Alkylation , Chemical Phenomena , Chemistry , Molecular Conformation , Structure-Activity Relationship , Surface-Active AgentsSubject(s)
Choline/analogs & derivatives , Nitrobenzoates , Chemical Phenomena , Chemistry , Detergents , Hydrolysis , MicellesABSTRACT
The reactions of the cobalozime Co (DH)-2 and the related Co(DOH)DOpn0 are strongly catalyzed by cationic micelles of cetyltrimethylammonium bromide (CTABr). The rate enhancements for the cobaloxime reaction and for that of Co (DOH)DOpn0 (in parentheses) are: EtBr approximately 1 (8.5); n-C5H11Cl, 220 (200); ClCH2CO-2, 420 (173); ClCH2CH2CO-2, 373. Anionic micelles of sodium lauryl sulfate inhibit the reaction of Co(DOH)DOpn0 with ClCH2CO-2, but do not affect that with n-C5H11Cl. The reactions of Co(DOH)DOpn0, like those of the cobaloxime are SN2 displacements and in the absence of surfactant in MeOH n-PrBr is more reactive than iso-PrBr.
