Solution properties of octyl-β-D-glucoside. Part 2: Thermodynamics of micelle formation

Solution properties of octyl--D-glucoside have been examined in a wide temperature and concentration range, by means of freezing point depression, volumetric and calorimetric methods. Partial molal quantities and the variations consequent to micellization have been evaluated and discussed. Strong support to the hypothesis of a growth of the micellar aggregates was inferred from heat capacity findings.     

Liquid-liquid partition and aqueous phase hydration of beryllium β-diketonates

Partition coefficients of four beryllium β-diketonates of two homologous series in aqueous NaClO₄ solution/n-hexane systems have been measured as functions of temperature (5–45°C) and of sodium perchlorate concentration (0–3 M). The ligands examined were: acetylacetone, propionylacetone, 3-methylacetylacetone, and 3-ethylacetylacetone. ΔG°, ΔH°, ΔS°, and ΔC°_p2 values for the partition processes have been evaluated as well as salting-out coefficients of the chelates and the corresponding ΔH° and ΔS° values.The results have been interpreted in terms of water structure changes (hydrophobic hydration) and of specific hydration in the outer coordination sphere of the coordinatively saturated chelates (hydration of the bonded ligands). The effect of changing both number and position of the CH₂ groups in the ligand molecules on ΔG°_p can be described using the surface area approach to the hydrophobic interaction. Irregularities in the remaining thermodynamic quantities indicate, however, a possibility of changes in the outer-sphere hydration of the chelates, probably due to the inductive effect of the ligand substituents.A contribution from the outer-sphere hydration must not be neglected when analysing thermodynamics of extraction of metal complexes.     

Photo-oxidative degradation of polyethylene: Effect of polymer characteristics on chemical changes and mechanical properties. Part 1—Quenched polyethylene

Photo-oxidative degradation of quenched samples of linear low density (LLD), medium density (MD) and two kinds of high density (HD) polyethylene (PE) films was studied using a medium-pressure mercury lamp. Greater amounts of crosslinking and build up of oxidation products were noticed in LLDPE than the other samples. The primary products of interaction between dienes and oxygen are considered to participate in the initiation of the photo-oxidation reactions. Using the FT-IR difference spectrum technique, the amount of branch concentration in the photo-irradiated PE samples was determined. Oxidation damage at the boundary region between crystalline and amorphous phases is considered to be important in determining the embrittlement time.     

Vibrational and thermodynamic properties of β-HMX: a first-principles investigation

Thermodynamic properties of β-HMX crystal are investigated using the quasi-harmonic approximation and density functional theory within the local density approximation (LDA), generalized gradient approximation (GGA), and GGA + empirical van der Waals (vdW) correction. It is found that GGA well describes the thermal expansion coefficient and heat capacity but fails to produce correct bulk modulus and equilibrium volume. The vdW correction improves the bulk modulus and volume, but worsens the thermal expansion coefficient and heat capacity. In contrast, LDA describes all thermodynamic properties with reasonable accuracy, and overall is a good exchange-correlation functional for β-HMX molecular crystal. The results also demonstrate significant contributions of phonons to the equation of state. The static calculation of equilibrium volume for β-HMX differs from the room-temperature value incorporating lattice vibrations by over 5%. Therefore, for molecular crystals, it is essential to include phonon contributions when calculated equation of state is compared with experimental data at ambient condition.     

Solution and surface properties of amphiphilic drug – nonelectrolyte systems

The surface tension values of amphiphilic drugs amitriptyline hydrochloride (AMT, an antidepressant) and promethazine hydrochloride (PMT, a phenothiazine) solutions in the presence of different fixed concentrations of alcohols (ethanol to octanol) and sugars were measured by the ring detachment method. The results indicated that long-chain alcohols form mixed micelles with both the drugs (as critical micelle concentration, cmc, decreases in their presence). Short-chain alcohols remain in aqueous phase and almost constant cmc values were obtained. Sugars, by increasing the hydrophobic interactions, decrease the drug cmcs. Maximum surface excess concentration at the air/solution interface (Γ_max) decreases for long-chain alcohols and sugars, but remains constant for short-chain alcohols. The minimum area per drug molecule (A _min) follows the opposite trend.     

Synthesis and photoluminescent properties of benzodioxan β-aminoketones

A series of benzodioxan β-aminoketones with various substituents in their carbonyl and amino groups are prepared and their photoluminescence spectra are studied. Comparison of the luminescence spectra of β-amino-7-propionyl-1,4-bexodioxane and o-aminophenylethyl ketone demonstrates that the presence of an ethylendioxy fragment in the aromatic region of β-aminoketones increases the intensity of their luminescence in the blue region of the spectra. The photoluminescence intensity of the synthesized benzodioxane β-aminoketones depends on the nature of the substituent when carbonyl carbon is present and decreases in the sequence C₂H₅ > C₃H₇ > CH(CH₃)₂ > C₆H₅. Introduction of a substituent in the amino group of benzodioxane β-aminoketones reduces the intensity of luminescence.     

synthesis and properties of β-brominated metal complexes of meso-triphenylcorrole

Spectral properties and chemical stability of Mn(III), Mn(IV), Fe(III), Fe(IV), and Cu(III) complexes of β-octabromotriphenylcorrole [(β-Br)₈(ms-Ph)₃Cor], synthesized from β-unsubstituted compounds by their reaction with molecular bromine, were studied. Cyclic voltammetry, electron microscopy, and X-ray spectral microanalysis were used to obtain electrochemical characteristics of metal corroles M(β-Br)₈(ms-Ph)₃Cor and gain insight into the surface texture of active catalysts on the basis of metal corroles. The electron-acceptor β-bromine substitution in the MCor macrocycle shifts the equilibrium in electron-donor solvents to lower oxidation states of the metals and also stabilizes manganese and destabilizes copper complexes in the protondonor medium HOAc-H₂SO₄. The electrocatalytic activity of the complexes in the reduction of molecular oxygen depends on the nature of the ligand and increases in the order Mn ≤ Cu ? Fe in the case of β-octabrominated macrocycles. The character of distribution of active centers on the surface of the catalysts was established for the first time.     

13C NMR of carbonyl compounds -4. Solution conformation of β-ionone and related dienones

The steric factors relevant for the conformations of β-ionone and structurally related compounds were studied by dynamic n.m.r. and ¹H,¹H-NOE measurements.     

Chromatographic characterisation of ordered mesoporous silicas. Part II: Acceptor–donor properties

The ordered mesoporous siliceous materials: MCM41C16, MCM41C16-SH and MCM41C16-NH₂ (known as MCMs) having different surface functionalities were studied by inverse gas chromatography to characterise their acceptor-donor properties. The DN values denoting the donor number in the Gutmann scale and the AN* values denoting the acceptor number in the Riddle–Fowkes scale have been chosen in the estimation of the electron-acceptor parameter K_A and electron-donor parameter K_D values. The number and kind of the employed adsorbates have an influence on the results obtained. The problem of the number of adsorbates employed has been considered in the light of both results obtained in the present study and the data available in the literature for siliceous adsorbents with randomly ordered structures. Complementary information was obtained by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy.     

The reaction of β-dicarbonyl compounds with trifluoromethylsulphenyl chloride. Part I. CF3S-substituted esters,anilides of β-keto acids,and their Schiff bases: Synthesis and stability.

The reactions of the β-keto acid derivatives with trifluoromethylsulphenyl chloride were carried out to give the α-SCF₃ substituted esters, anilides, and their Schiff bases of acetyl- and benzoylacetic acids. Ethyl esters of α-(trifluoromethylthio)acetoacetic and α-(trifluoromethylthio)benzoylacetic acids heated in dimethylsulphoxide/water solution give trifluoromethylthioacetone and ω-(trifluoromethylthio)acetophenone respectively, whereas with potassium hydroxide solution they form trifluoromethylthioacetic acid in a good yield.     

Solution properties and mesophase formation of 4‐phenyl‐benzoylcellulose

Cellulose samples were derivatized in dimethylacetamide/LiCl (DMAc/LiCl) to give 4phenylbenzoylcelluloses (PBCs). The process is quantitative and leads to an highly substituted product, as verified by elemental analysis, IR and ¹³CNMR spectroscopy. PBC samples were characterized by viscometric and light scattering measurements in DMAc. The persistance length q is used to evaluate the theoretical critical volume fraction for mesophase formation (v _th, which has been found higher than the experimental critical one (v _exp)     

Synthesis and acid-base properties of new β-diaminophosphoryl compounds

Russian Journal of Organic Chemistry -     

Interfacial and emulsifying properties of designed β-strand peptides

The structural and surfactant properties of a series of amphipathic β-strand peptides have been studied as a function of pH. Each nine-residue peptide has a framework of hydrophobic proline and phenylalanine amino acid residues, alternating with acidic or basic amino acids to give a sequence closely related to known β-sheet formers. Surface activity, interfacial mechanical properties, electronic circular dichroism (ECD), droplet sizing and zeta potential measurements were used to gain an overview of the peptide behavior as the molecular charge varied from ±4 to 0 with pH. ECD data suggest that the peptides form polyproline-type helices in bulk aqueous solution when highly charged, but may fold to β-hairpins rather than β-sheets when uncharged. In the uncharged state, the peptides adsorb readily at a macroscopic fluid interface to form mechanically strong interfacial films, but tend to give large droplet sizes on emulsification, apparently due to flocculation at a low droplet zeta potential. In contrast, highly charged peptide states gave a low interfacial coverage, but retained good emulsifying activity as judged by droplet size. Best emulsification was generally seen for intermediate charged states of the peptides, possibly representing a compromise between droplet zeta potential and interfacial binding affinity. The emulsifying properties of β-strand peptides have not been previously reported. Understanding the interfacial properties of such peptides is important to their potential development as biosurfactants.     

Synthesis of β-cyclodextrin-lysozyme conjugates and their physicochemical and biochemical properties

Recently a great interest in the field of protein engineering and the design of innovative drug delivery systems employing specific ligands such as cyclodextrins is observed. The paper reports the solid state, thermal method for protein coupling with β-cyclodextrin and the physicochemical and biological properties of the obtained conjugates. The structure of the obtained conjugates was investigated via liquid chromatography-mass spectrometry, dynamic light scattering and circular dichroism analysis. The presented conjugates were biologically active and covalently bound β-cyclodextrin preserved the ability to form inclusion complexes with the model compound. This report demonstrates the great potential of cyclodextrin as a modifying unit that can be used to modulate the properties of therapeutic proteins, additionally giving such conjugates the possibility to transport many therapeutic substances in the form of inclusion complexes. In addition, the paper presents the potential of protein-cyclodextrin conjugates to construct innovative bioactive molecules for biological and medical applications.     

Pore size or geometry: which determines the shape and inverse-shape selective adsorption of alkane isomers?

The adsorption of pure pentane (C(5)) isomers and their ternary mixture is simulated in a series of carbon nanoslits. With decreasing nanoslit pore size, shape selective adsorption first occurs in the order of nC(5) > or = iC(5) > neoC(5) due to the configurational entropy effect, then inverse-shape selective adsorption occurs in the order of nC(5) < iC(5) < or = neoC(5) due to the area entropy effect, and finally no adsorption occurs. The entropy effects lead to a large adsorptive separation among the C(5) isomers from their mixture. Similar behavior has been observed from the simulation of C(5) adsorption in carbon nanotubes with variation in pore size. These results reveal that pore size rather than geometry determines the shape and inverse-shape selective adsorption of alkane isomers in nanopores.     

Mixed micellar systems of octyl β,d-glucopyranoside with a nonionic surfactant and a water-soluble polymer

We have made a comparative study between the micellar regions of the octyl -d-glucoside (OG)–tetraethylene glycol monododecyl ether and the OG–poly(ethylene glycol) 20,000 systems by means of surface tension and viscosimetric measurements. The incorporation of the tetraethylene glycol monododecyl ether nonionic surfactant in the OG micelles decreases the critical micelle concentration, whereas the presence of polymer increases it. The nonionic surfactant mixture exhibits nonideal mixing behaviour. The data fit to Rubinghs treatment with a value of –5.1, which implies a modest attraction between both surfactants. The surfactant–poly(ethylene glycol) 20,000 system does not form mixed micelles. The incorporation of polymer increases the critical micelle concentration of the surfactant. The viscosity for the surfactant–polymer system is higher than that for the pure polymer, demonstrating a surfactant-induced structuring.