Solubilization of styrene in the catanionic system dodecyltrimethylammonium hydroxide–n′-dodecanephosphonic acid

 The solubilization of styrene in micelles of the catanionic surfactant dodecyltrimethylammonium hydroxide (DTAOH)–n-dodecane-phosphonic acid (DPA) was studied by UV–Vis. spectrometry, as a function of the DTAOH:DPA proportion in the surfactant mixture. The styrene molecules are adsorbed at the surface of the micelles, with the vinyl group closer to the hydrocarbon core than the aromatic ring, which is oriented to the water. In micelles with an excess of DTAOH, the dielectric constant of the water surrounding the micelles was strongly affected by the non-neutralized –N(CH₃)⁺ ₃ groups at the Stem layer. In micelles with an excess of DPA, the –PO₃H₂ groups which are not neutralized by –N(CH₃)⁺ ₃, remain almost unionized and hydrogen-bonded. The effect of the micellar surface on the surrounding water dielectric constant dropped sharply. The dielectric constant in the hydrogen-bonded polar layer is ∼65, rising to the value of pure water very close to the micellar surface. Received: 2 September 1997 Accepted: 20 October 1997     

Direct potentiometric titration of chloride and fluoride ions in reversed micelles of an ethoxylated surfactant

The possibility of the potentiometric titration of Cl^– and F^– ions directly in reversed micelles of the ethoxylated surfactant (Neonol APh₉-4) in n-decane is shown. The potential change of the indicator electrode (silver chloride and lanthanum fluoride) only depends on the ion concentration in the aqueous pseudophase of the reversed micelles and is independent of the aqueous phase concentration in n-decane in the region of concentrations from 4 to 0.2 vol %. The determination of the micelle size of Neonol APh₉-4 in the precipitation titration of Cl^– and F^– ions by photon correlation spectroscopy showed the formation of nanoparticles of AgCl and LaF₃ of dimensions limited by original micelle size (r_hd = 6 to 11 nm). The growth of AgCl and LaF₃ nanoparticles was studied at a shortage and excess of the titrant and in the point of equivalence. Received: 23 April 1999 / Revised: 15 July 1999 / Accepted: 19 July 1999     

A New Model for Multiply Charged Adduct Formation Between Peptides and Anions in Electrospray Mass Spectrometry

A new model has been developed to account for adduct formation on multiply charged peptides observed in negative ion electrospray mass spectrometry. To obtain a stable adduct, the model necessitates an approximate matching of apparent gas-phase basicity (GB_app) of a given proton bearing site on the peptide with the gas-phase basicity (GB) of the anion attaching at that site. Evidence supporting the model is derived from the fact that for [Glu] Fibrinopeptide B, higher GB anions dominated in adducts observed at higher negative charge states, whereas lower GB anions appeared predominately in lower charge state adducts. Singly charged adducts were only observed for lower GB anions: HSO₄^–, I^–, CF₃COO^–. Ions that have medium GBs (NO₃^–, Br^–, H₂PO₄^–) only form adducts having −2 charge states, whereas Cl^– (higher GB) can form adducts having −3 charge states. The model portends that (1) carboxylate groups are much more basic than available amino groups; (2) apparent GBs of the various carboxylate groups on peptides do not vary substantially from one another; and (3) apparent GBs of the individual carboxylate and amino sites do not behave independently. This model was developed for negative ion attachment but an analogous mechanism is also proposed for the positive ion mode wherein (1) binding of a neutral at an amino site polarizes this amino group, but hardly affects apparent GBs of other sites; (2) proton addition (charge state augmentation) at one site can decrease the instrinsic GBs of other potential protonation sites and lower their apparent GBs.     

Stability against aggregation of bovine casein micelles in the presence of acidic and alkaline gelatin

The effect of the presence of colloidal dispersed and molecular dispersed acidic (type A) and alkaline (type B) gelatins with similar molecular weight and size but different isoelectric points (7.9 and 4.9) on the stability against aggregation of bovine casein micelles was investigated by turbidimetric titration and laser techniques, over a wide range of biopolymers concentrations, gelatin/casein ratio in the initial mixture (0.03–20), pH (4.9–6.7) and ionic strength (10⁻³(milk salts)–1.0 NaCl), using glucono-δ-lactone (GL) as acidifier. Aggregates of acid gelatin A interact with the oppositely charged micellar casein at an ionic strength of around 10⁻³(milk salts) and pH 6.7 resulting in the formation of an electroneutral complex by ionic bonds between the carboxyl groups of casein and the amino groups of the gelatin molecules. The complexes obtained are polynuclear, the aggregation of which is not as sensitive to pH as that of free casein micelles. Aggregation of such complexes is the result of bridging flocculation. The “molar” ratio gelatin aggregates/casein micelles in the mixed aggregates is 4/1. The complexes are formed and stabilised via electrostatic interaction rather than through hydrogen bonds or hydrophobic interaction. In the presence of an excess of gelatin molecules in the initial mixture a charged gelatin–casein complex forms and some dissociation of casein micelles occurs and, as a consequence, soluble complexes are obtained. During the addition of alkaline gelatin B aggregates to the micellar casein solution and subsequent acidification of the mixture by GL, no effect of the presence of gelatin B on the stability of micellar casein was observed. Received: 28 March 2000 Accepted: 5 October 2000     

Aladan scanning: The structure-activity relationship of dynorphin A

An unnatural amino acid, β-[6′-(N, N-dimethyl)amino-2′-naphthoyl]alanine (Ald) showing polarity-sen sitive fluorescence characteristics, was synthesized. A thorough Ald-scan of dynorphin A (Dyn A), the putative endogenous ligand for κ opioid receptors, was then performed. Replacement of the amino acid residues in positions 5, 8, 10, 12 or 14 of Dyn A(1-13)-NH2 with Ald resulted in compounds that had almost equal κ binding affinity compared with that of the parent compound; on the other hand, substi-tution o...     

The effect of the melting of the collagen-like gelatin aggregates on the stability against aggregation of the bovine casein micelles

The effect of the melting of the collagen-like acid and alkaline gelatin aggregates on the stability against aggregation of bovine casein micelles was investigated by turbidimetry, DSC and circular dichroism in the wide range of biopolymers concentrations, gelatin/casein ratio (R) in initial mixture (R=0.03–20), pH (4.9–6.7), ionic strength (I=10⁻³ to 1.0/NaCl/), and temperature (10°–70 °C), using glucono-δ-lactone (GL) as acidifier. At low ionic strength (10⁻³/milk salts/) and neutral pH interaction between gelatin molecules and casein micelles is suppressed significantly above 36 °C. The melting of the collagen-like acidic gelatin above this temperature shifts the pH at which the complex formation is maximal to the acidic range. The cause may be that some of the functional ionized groups of gelatin molecules are inaccessible due to the conformational changes. The presence of gelatin B molecules had no effect on the aggregation stability of micellar casein in the range 0.03<R<20. At very high total protein concentration (above 10%) depletion flocculation of casein micelles was observed. The reason for the very high stability of casein micelles in this case cannot be explained by volume exclusion. Received: 28 March 2000 Accepted: 5 October 2000     

Guest editor's tribute to Friedrich Baucke on the occasion of his 80th birthday

The results of experiments where Tl⁺ and Pb²⁺ ions are electrolysed into a sodium borate glass (35 mol% Na₂O and 50 °C) are brought up to date in order to take into account recent developments in the chemistry of borate glasses. It is first necessary to consider the unique chemistry of the oxide(-II) species in terms of its electronegativity, electronic polarisability and acid–base properties, and the significant relationship between these is discussed. It is described how the Lewis basicity of oxidic materials such as glasses can be expressed quantitatively on the optical basicity scale and how determinations are made by various experimental methods. These methods include optical spectroscopy of ‘probe’ ions such as Tl⁺ or Pb²⁺, measurement of electronic polarisability and far-infrared spectroscopic ‘rattling’ frequencies of constituent metal ions. When Pb²⁺ ions are electrolysed into the sodium borate glass, it is found that there is migration of Na⁺ ions away from and of O²⁻ ions towards the (lead) anode with formation of PbO. There is almost complete depletion of Na₂O in the anode region so that the composition of the glass approximates to B₂O₃. A similar process occurs to a limited degree in the case of thallium, but the Tl⁺ ions are able to penetrate more deeply into the glass. Their ultraviolet ¹S₀ → ³P₁ frequency indicates that the sites they occupy have much greater basicity than the bulk glass. The two-site model of Kamitsos proposes that in borate glasses, there are higher and lower basicity sites, and the measured optical basicity of Tl⁺ indicates occupation of the higher sites. Since it has been shown that BO₄ groups in the glass are weakly basic, it is unlikely that they are involved in the higher sites. It is discussed how the higher site basicity implies greater covalency in the interaction of the Tl⁺ ion with the oxide(-II)s that constitute the pathway, and it is suggested that this is an important factor in the electromigration process.     

Dodecyltrimethylammonium bromide–disodium dodecanephosphonate mixed micelles

 The aqueous catanionic system dodecyltrimethylammonium bromide (DTAB)–disodiumdodecanephosphonate (DSDP) was studied by potentiometry, conductivity, surface tension, spectrometry and dye solubilization. No precipitation of neutral salts was found in the entire range of compositions studied. Up to four transitions were detected. The first transition, at about 0.001 mol dm⁻³, was probably related to a state change in the adsorption monolayer at the air/water interface. The second, at about 0.0065 mol dm⁻³, was probably related to the formation of ion pairs. The third transition was the critical micelle concentration which was analyzed with the pseudophase separation model and regular solution theory. The interaction between DTAB and DSDP molecules in micelles was weaker than in other cationic–anionic surfactant mixed micelles. Large, probably rodlike, micelles formed at the fourth transition at higher surfactant concentration. No vesicles or lamellar liquid crystals were detected. The adsorbed monolayer at the air/water interface was also studied by means of regular solution theory. It was much richer in DTAB than the micelles and the intermicellar solution. The interaction between DTAB and DSDP molecules at the air/water interface was very low. The results were explained on the basis of steric factors. Received: 6 January 1999 Accepted in revised form: 13 April 1999     

Micellar behavior of acrylamide– octylphenylpoly(oxyethylene) acrylate copolymer in aqueous solution

The copolymer of acrylamide and octylphenylpoly(oxyethylene) acrylate macromonomer (AM-C₈PhEO₇Ac) was synthesized and characterized by IR and NMR spectroscopy. The molecular weight of the copolymer was determined to be 1.21 × 10⁵ by static light scattering. The weight contents of AM and macromonomer were determined to be 67.8 and 32.2%, respectively, by elemental analysis. The micellar behavior of the copolymer in aqueous solution was studied by UV spectroscopy and atomic force microscopy (AFM). The molecules of AM-C₈PhEO₇Ac copolymer form monomolecular micelles in the concentration range 4 × 10⁻⁶ – 3 × 10⁻⁵ g/ml and polymolecular micelles at concentrations above 3 × 10⁻⁵ g/ml according to the UV analysis. The AFM images indicate that the monomolecular micelles are globular with diameters of 70 nm and have a narrow size distribution. The polymolecular micelles can be globular or cylindrical depending on the concentration, and have a wide size distribution. Received: 10 February 1999 Accepted in revised form: 28 June 1999     

Isoparametric correlations in reactions of 4-R-N-arylpyridinium salts with arylamines

Isoparametric dependencies of the structure of the reagents (including non-catalytic rate constants, substitution constants σ⁰, basicity constants, and charges at the reaction centers) have been obtained for the reactions between 4-R-N-(2,4-dinitrophenyl)pyridinium salts with arylamines. The electron-acceptor 4-R-substituents studied reduced the positive charge on the reaction center (the α-atom) and the nitrogen atom of the N-arylpyridinium cation. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Luxembourg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 231–235, July–August, 1999.     

Intensity-tunable micelles and films containing bimetal ions—europium(III) and terbium(III)

In this paper, multicolored micelles were prepared by coordination of lanthanide(III) (europium(III) (Eu(III)) and terbium(III) (Tb(III))) ions with block copolymer in different molar ratios of n _Eu(III)/n _Tb(III). The micelles formed by polymer–Eu(III)/Tb(III) could emit higher quantum yield luminescence than the mixture of polymer–Eu(III) micelles and polymer–Tb(III) micelles. The micelles containing Eu(III) and Tb(III) could emit a yellow-green color, and the intensity varied with the molar ratios of n _Eu(III)/n _Tb(III). In the constant concentrations of Eu(III) and 1,10-phenanthroline (Phen), the intensity of ⁵D₀→⁷F₂ increased with the addition of Tb(III), and the intensity of ⁵D₄→⁷F₅ decreased with the increasing of Eu(III) in the constant concentrations of Tb(III) and Phen. All the multicolored micelles could be spin-coated as intensity-tunable films.     

Receptor properties of calix[4]resorcinarenes toward tetramethylammonium and choline cations in micellar solutions of sodium dodecyl sulfate

Concentration range of solubilization of calix[4]resorcinarene (H₈L) in sodium dodecyl sulfate (SDS) micelles was found. The interaction of the deprotonated form of H8L (tetraanions [H₄L]⁴⁻) with tetramethylammonium (TMA) and choline cations in micellar solutions of SDS was studied by pH-metry and NMR spectroscopy. The concentration dependences of the change in the cloud point in a multicomponent system TMA (choline)-[H₄L]⁴-SDS-tetrabutylammonium bromide were determined. A correlation of these dependences with host-guest binding processes was found. The sharp change in the cloud points of the corresponding micellar solutions in concentration regions of TMA (0-5·10⁻⁴ mol L⁻¹) and choline (0–1.1· 10⁻³ mol L⁻¹) is caused by the formation of inclusion complexes TMA (choline)-[H₄L]⁴⁻ at the interface of the aqueous and micellar pseudophases. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1366–1371, August, 2006.     

Micellar effects of surfactants in cleavage of 4-nitro-phenyl diethyl phosphonate by hydroperoxide anion

We have studied the nucleophilicity of the hydroperoxide anion relative to 4-nitrophenyl diethyl phosphonate (NPDEPS) in the presence of cetyltrimethylammonium bromide (water, 25 °C) while varying the acidity of the medium and the hydroperoxide anion concentration over a broad range. The increase in the reaction rate when the reaction is transferred to a micellar pseudophase is as high as ∼10-fold, which is explained by concentration effects. In CTAB micelles, as in water, the hydroperoxide ion is one of the most effective α-nucleophiles, and the size of the α-effect, characterized by the ratio of the second-order rate constants for reactions of HOO⁻ and OH⁻ anions with NPDEPS, remains practically constant and reaches a value of ∼50-fold. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 6, pp. 357–363, November–December, 2006.     

Temperature structural transformations of reverse micelles of oxyethylated surfactants

The dependence of the hydrodynamic radius of reverse micelles of Tergitol NP-4 on temperature (20–50°C), solubilization capacity (0–7 vol %), electrolyte composition (NH₄NO₃, KNO₃, HNO₃, NH₄OH, and KOH), and electrolyte concentration (0–8 mol/l) in an aqueous pseudophase was studied by photon-correlation spectroscopy. The hydrodynamic radius of micelles was shown to decrease with increasing temperature regardless of the concentration and type of electrolyte, and spherical micelles were formed in the process. It was ascertained that temperature aligns the features of interaction between solubilisate and micelles due to dehydration of the surfactant molecules: the radius of spherical micelles at 50°C depended only on solubilization capacity.     

Low-concentration aqueous solutions of undecenoic acid and sodium undecenoate

The behaviors of low-concentration aqueous solutions of 10-undecenoic acid and its sodium salt were studied by several techniques. The acid does not have a critical micelle concentration, but gives an emulsion of very small droplets at (0.8–1) ×  10⁻⁴ mol dm⁻³. The emulsion was clearly visible by eye at 0.002 mol dm⁻³. The sodium salt has a stepwise aggregation process, giving premicellar aggregates at 0.023 ± 0.008 mol dm⁻³, which grow to form micelles at 0.117 ± 0.007 mol dm⁻³. The compositions of the solution and the micelles were also studied. Received: 25 February 1999 Accepted in revised form: 21 June 1999     

Reactivity of a Ti–45.9Al–8Nb alloy in air at 700–900°C

A Ti–45.9Al–8Nb (at%) alloy with a lamellar structure (γ+α₂) was oxidised in air at 700, 800, 850 and 900°C in isothermal and thermal cycling conditions. The reaction progress was followed by thermogravimetric measurements. In isothermal conditions the oxidation kinetics followed approximately a parabolic rate law and the rate constants ranged from about 10^–12 kg² m^–4 s^–1 at 700°C to 10^–10 kg² m^–4 s^–1 at 900°C. The oxide scales were built of Al₂O₃ and TiO₂, the former being the main component of the outermost layer. The oxidation behaviour of Ti–45.9Al–8Nb was referred to a commercial titanium alloy, WT4 (Ti–6Al–1Mn), and selected oxidation-resistant alloys.     

Sampling and determination of hydrogen cyanide in cigarette smoke

A method for sampling and determination of hydrogen cyanide in cigarette smoke is described. Cigarette smoke is filtered through a glass fiber filter paper, and only gaseous compounds, such as hydrogen cyanide, are collected in a dilute sodium hydroxide solution. The cyanide is determined spectrophotometrically at 550 nm by the isonicotinic acid–pyrazolone method. Maximum absorbance is achieved within 10 min at room temperature, and remains constant for about 20 min. Beer’s law is obeyed in the range 0.04∼0.80 μg mL^–1 cyanide, with a molar absorptivity of 3.48 × 10⁴ L mol^–1 cm^–1. Received: 30 November 1998 / Revised: 21 April 1999 / Accepted: 30 April 1999     

Cleavable dicationic surfactant micellar system for the decomposition of organophosphorus compounds

A dimeric (gemini) surfactant containing cleavable ester groups has been synthesized and studied. The new surfactant has a low critical micelle concentration (2.7∙10^–5 mol/L) and Krafft temperature (≤0°C). Alkaline hydrolysis of 4-nitrophenyl diethyl phosphonate and 4-nitrophenyl diethyl phosphate in the presence of micelles of gemini surfactant I proceeds 30-144 times more rapidly than in water. Chemical cleavage of gemini surfactant I in an alkaline medium is achieved in 96 h.     

Sampling and determination of hydrogen cyanide in cigarette smoke

A method for sampling and determination of hydrogen cyanide in cigarette smoke is described. Cigarette smoke is filtered through a glass fiber filter paper, and only gaseous compounds, such as hydrogen cyanide, are collected in a dilute sodium hydroxide solution. The cyanide is determined spectrophotometrically at 550 nm by the isonicotinic acid–pyrazolone method. Maximum absorbance is achieved within 10 min at room temperature, and remains constant for about 20 min. Beer’s law is obeyed in the range 0.04∼0.80 μg mL^–1 cyanide, with a molar absorptivity of 3.48 × 10⁴ L mol^–1 cm^–1. Received: 30 November 1998 / Revised: 21 April 1999 / Accepted: 30 April 1999     

Basicity of 2-phenyl-5-R-1,3,4-oxadiazoles

We have studied the basicity of 2-phenyl-5-R-1,3,4-oxadiazoles (R = H, Me, CH₂Ph, t-Bu, CH₂Cl, CCl₃, CF₃) in aqueous sulfuric acid solutions. These compounds are weak organic bases (pK_BH ⁺ is −1.8 to −5.2). The values of pK_BH ⁺ determined on the H₀ and X acidity function scales agree well with each other. The substituent at the 5 position has a substantial effect on the basicity of the 1,3,4-oxadiazole ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 748–756, May, 2006.