The Spectral Displacement Technique for Determining the Binding Constants of β-Cyclodextrin – Alkyltrimethylammonium Inclusion Complexes

A survey of the literature reveals that the spectroscopic displacement method, in which phenolphthalein is used as a competitive chromophore to determine binding constants of β-cyclodextrin with surfactants was successful in the case of homologous hydrocarbon and fluorocarbon anionic surfactants. We show here that this method can be applied also for homologous alkyltrimethylammonium bromides (with alkyl varying from octyl- to hexadecyl) under the condition that the concentration of the cationic surfactant is distinctly lower than the value of itscritical micelle concentration.     

Binding of Benzyltrimethylammonium Bromide and its Alkyldimethylbenzylammonium Homologues by β-Cyclodextrin in Water

The binding constants, K′, for the reaction between some alkyldimethylbenzylammonium bromide homologues (alkyl = methyl, ethyl, propyl, butyl, hexyl, decyl, and dodecyl, respectively) and β-cyclodextrin in water at 25.0 ± 0.1 ^∘C have been determined, by applying the spectral displacement technique with phenolphthalein as the displacing anion. It has been shown that the ln K′ values increase linearly with the number of carbon atoms in the alkyl chain for the salts whose alkyl chain has at least four carbon atoms. The ln K′ values estimated for the parent compound benzyltrimetylammonium bromide and its two nearest homologues are distinctly lower than might be expected by extrapolation of the linear relation found for the higher homologues. Assuming that it is the organic cation that undergoes association with β-cyclodextrin, then one may suppose that a change occurs in the mode of inclusion of the cation upon passing to higher homologues. In the case of the lighter homologues, it is the phenylene group that undergoes inclusion. This model of inclusion is confirmed by analysis of rotating-frame overhauser effect spectroscopy (ROESY) spectra.     

Embeddings of general blowups of abelian surfaces

Blowups of algebraic surfaces polarized by tensor powers of ample line bundles were studied by Coppens [8]. In this note we complete the picture in the case of abelian surfaces studying blowups of surfaces polarized by primitive line bundles. Received: 16 November 1999 / Revised version: 13 June 2000     

On 3-syzygy and unexpected plane curves

Geometriae Dedicata - We prove a new inequality relating volume to length of closed geodesics on area minimizers for generic metrics on the complex projective plane. We exploit recent regularity...     

Highly stereoselective synthesis of 2-deoxy-α- glycosides and α-disaccharides

Highly stereoselective synthesis of 2-deoxy-α-glycosides including disaccharides is described, using S-(2-deoxyglycosyl)phosphorodithioates as glycosyl donors, in the presence of silver perchlorate in acetonitrile     

Surface tension studies on the complexation of dodecylpyridinium chloride byβ-cyclodextrin in aqueous electrolyte solutions

Surface tension measurements have been performed at 25° C for aqueous mixtures of dodecylpyridinium chloride and -cyclodextrin in 0.1 M NaCl. Data analyses assuming 1:1 stoichiometry were applied to estimate the complexation constant of the host-guest complex formation. The technique yields consistent results for solutions with a swamping, constant concentration of a simple inorganic electrolyte.     

NEW NATURAL SULFOXIDES OF NUPHAR ORIGIN. STRUCTURE,CHEMISTRY, PUMMERER REARRANGEMENT

Abstract

Further studies on basic compounds from Nuphar luteum L. Sm. resulted in isolation of a new group of sulfoxides with thiohemiaminal type of structure.     

10-Methylacridinium ion as a fluorimetric probe measuring the activity of halide anions in aqueous solutions of cationic surfactants

The quenching of fluorescence of 10-methylacridinium ion by inorganic anions in aerated aqueous solutions was studied at room temperature. In the case of cationic surfactants, with chloride and bromide anions as counterions, characteristic breaks on the Stern-Volmer plots could be observed at concentrations corresponding to the critical micelle concentration of the surfactants. It is shown that the ratio of the slopes of the two linear fragments of the plots, in the micellar and premicellar concentration ranges, gives an estimate of the value of the ionization degree, alpha, of the micelles. This approach is applicable also in aqueous-alcohol systems.     

Ortho- and para-substituted Hoveyda-Grubbs carbenes. An improved synthesis of highly efficient metathesis initiators

A novel highly efficient and general route to various 3- and 5-substituted 2-alkoxystyrenes, required for the preparation of Hoveyda-Grubbs catalysts, is described.