Mixture Of Mono Research Articles

1,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene: Regioselective ring opening of its α,β-epoxybis(silane) with some nucleophiles

Abstract The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyllithium, (Me3Si)3CLi, in Et2O gives disubstituted vinylbis(silane) 1 which reacts with MCPBA in CH2Cl2 at r.t. to afford mixture of mono and disubstituted epoxybis(silanes) 3 and 2. Vinylbis(silane) 1 can be completely converted into epoxybis(silane) 2 with an excess amount of MCPBA. The compound 2 was reacted with various reagents such as HX (X = Cl, Br), H2SO4, LiAlH4 and MeLi/CuI and give the related products.

Characterization of Z‐RAFT Star Polymerization of Butyl acrylate by Size‐Exclusion Chromatography

AbstractZ‐RAFT star polymerization of butyl acrylate using multifunctional trithiocarbonate‐type RAFT agents carrying methyl propionate as the leaving group were used to form star polymers having 3, 4, and 6 arms. The polymerizations showed well controlled behavior up to high monomer conversions. By using a mixture of mono‐ and multifunctional RAFT agents, arm and star polymer were obtained simultaneously within a single RAFT polymerization, which enabled the evaluation of the apparent arm numbers. The desired topology of the star polymers was found being present already from the early phase of polymerization on. The apparent arm number slightly increases at very high monomer conversions in accordance to earlier reported star coupling reactions. Correction factors for conventionally calibrated SEC showed excellent agreement with data for polystyrene stars, indicating that the contraction of the hydrodynamic volume in comparison to linear polymer is only dependent on the polymer topology. The evaluation of absolute molar masses of star polymers was however limited by the accuracy of the conventional calibration.

Sol–gel synthesis and structural characterisation of P2O5–B2O3–Na2O glasses for biomedical applications

Glasses in the system 40(P2O5)–x(B2O3)–(60 − x)(Na2O) (10 ≤ x ≤ 25 mol%) were prepared by the sol–gel technique. A mixture of mono- and diethylphosphates was used as precursor for P2O5, boric acid and sodium methoxide were used as source compounds for B2O3 and Na2O, respectively. The dried gels obtained were heat treated at 200, 300 and 400 °C. Structural development occurring during heat treatment and changes with composition were investigated using X-ray diffraction, thermal analysis, infrared spectroscopy, 11B and 31P solid state NMR. Systems with x = 20 and x = 25 mol% are amorphous up to 400 °C, whereas systems with lower B2O3 content are partially crystalline. This work extends sol–gel preparation of amorphous borophosphate systems having P2O5 as the main component.

Bidentate salicylaldiminato tin(ii) complexes and their use as lactide polymerisation initiators

A study of the reactions of several salicylaldimines (ortho-iminophenols) with Sn(NMe2)2 reveals that the sterics and electronics of the N-substituent play a principal role in determining the product mixture. Thus mono(chelate) tin(II) amides have only been isolated with bulky N-anilido substituents, including [2,4-X2-6-{CHN-2,6-iPr2C6H3}-C6H2O]Sn(-NMe2)]2, X = Cl, 1; X = I, 2 and [2,4-Cl2-6-{CHN-2,4,6-tBu3C6H2}-C6H2O]Sn(NMe2), 3. With smaller N-aryl and N-alkyl substituted salicylaldimines, mixtures of mono- and bis- chelate complexes are formed, even if the phenoxide ring bears large tert-butyl substituents. Further, when the anilido group bears electron-withdrawing substituents, the imino carbon is activated towards nucleophilic attack (as demonstrated by the formation of [2,4-tBu2-6-{CH(NMe2)N-2,4,6-Br3C6H2}-C6H2O]Sn, 4); no such reactivity has been observed when the halo substituents are located on the phenolic ring. The abilities of complexes 1-4 to initiate the ring-opening polymerisation of rac-lactide have also been studied. Complexes 1, 2 and 4 possess comparitively similar activities, but propagation with 3 is at least one order of magnitude slower, an observation rationalised in terms of steric congestion.

Supramolecular microcontact printing with receptor-functionalized PDMS stamps

Poly(dimethylsiloxane) (PDMS) stamps have been functionalized with β-cyclodextrin (β-CD) receptors to achieve control over-inking and transfer of specific molecules by supramolecular microcontact printing (SµCP). Monovalent adamantyl ink molecules (lissamine-Ad) were self-assembled onto the β-CD host-covered stamps, which transferred the ink molecules onto a target substrate. The monovalent ink was recognized specifically from solutions containing other, nonbinding molecules with a selectivity of at least 4000. The adsorption of inks from a mixture of mono- and divalent guests was dominated by the divalent molecules owing to their higher binding strength. A host-functionalized silicon dioxide surface covered with a self-assembled ink monolayer was used as a supramolecular inkpad to ink a β-CD-functionalized stamp, which offered increased control over the number of ink molecules applied.

Macrocyclic host cyclophosphazenes from aminolysis of N3P3CI6 by bis-(2-ortho-aminophenoxyethyl)ether

AbstractAminolysis of N3P3CI6 by an oxodiamine, bis-(2-ortho-aminophenoxyethyl) ether, has been carried out under various experimental conditions and new products with different architectures have been obtained. The reaction in diethyl ether when using a Na2CO3-water interface process gives the mono-BINO as major product. Reaction on Al2O3/KOH leads to the spirocyclic compound, while, when the reaction is carried out in toluene in the presence of NEt3, a mixture of mono- and di-BINO products are obtained. These new products have been characterized by IR, 1H and 31P NMR spectroscopy.

Synthesis and GC-MS study of fluorinated esters derived from thrimethylolpropane

Zol-gel process was used to synthesize equilibrium mixtures of mono-, di-, and trimester derived from trimethylolpropane and perfluorocarboxylic acids. The elution order of the components of the mixtures from a weakly polar HP-5 column was established. The mass spectra of the synthesized compounds were studied. The GC-MS parameters of the products were compared with the respective parameters of their nonfluorinated analogs. The characteristics of the fluorinated esters have features determined by the esterification degree and the nature of the perfluoroalkyl groups, due to which these compounds can be identified in mixtures.

SYNTHESIS OF α-ZIRCONIUM PHOSPHATE FROM ACETYL ACETONATE SOLUTION; A COMPARATIVE SYNTHESIS STUDY OF α-ZrP

Three main routes of synthesis; namely the reflux, the direct precipitation, and the sol-gel methods, are used to prepare α-zirconium phosphate α-Zr(HPO4)2.2H2O or simply α-ZrP. Within each separate method of synthesis, different starting precursors and/or reaction conditions are tested for optimization to obtain the crystalline product. Different products were characterized using TGA-DTA data, SEM photos, N2-gas absorption-desorption measurements, and FT-IR absorption spectra. The products showed different extents of crystallinitiy as roughly or qualitatively shown by their XRD patterns. The results are explained on the basis of each synthesis route and reaction conditions. In contrast to the familiar results that the initial un-refluxed product of rapid precipitation is basically amorphous ZrP, a careful washing strategy confirmed that this is a crystalline ZrP contaminated with a minority of solid H3PO4. This is shown by the XRD patterns of this product after intercalation with butylamine. For sol-gel experiments, reflux could not greatly improve the crystallinity of the products obtained from a mixture of Zr(OPriso)4 and phosphoric acid solutions while a product obtained in presence of acetylacetone, as a complexing agent, presented some better tendency for crystallization with reflux. All products of refluxing Zr(OPriso)4 with a 1:1 mixture of mono- and diethyl phosphates were amorphous. Chemical analysis shows a reasonable agreement between the experimental ratios of P/Zr and the calculated values. Compared to other methods of synthesis, the direct precipitation seems to be more efficient in obtaining a product of good yield and improved crystallinity.

Deprotonative Metalation of Five-Membered Aromatic Heterocycles Using Mixed Lithium−Zinc Species

Deprotonation of benzoxazole, benzothiazole, benzo[b]thiophene, benzo[b]furan, N-Boc-protected indole and pyrrole, and N-phenylpyrazole using an in situ mixture of ZnCl(2).TMEDA (0.5 equiv) and lithium 2,2,6,6-tetramethylpiperidide (1.5 equiv) in THF at room temperature is described. The reaction was evidenced by trapping with iodine, regioselectively giving the expected functionalized derivatives in 52-73% yields. A mixture of mono- and disubstituted derivatives was obtained starting from thiazole. Cross-coupling reactions of 2-metalated benzo[b]thiophene and benzo[b]furan with heteroaromatic chlorides proved possible under palladium catalysis. A reaction pathway where the lithium amide and zinc diamide present in solution behave synergically was proposed for the deprotonation reaction, taking account of NMR and DFT studies carried out on the basic mixture.

Lithium-Mediated Zincation of Pyrazine, Pyridazine, Pyrimidine, and Quinoxaline

Deprotonation of pyrazine, pyridazine, pyrimidine, and quinoxaline using an in situ mixture of ZnCl2.TMEDA (0.5 equiv) and LiTMP (1.5 equiv) was studied. Pyrazine and pyrimidine were deprotonated in THF at room temperature, a result evidenced by trapping with I2. The competitive formation of dimer observed in net hexane was reduced by using cosolvents (TMEDA or THF). Starting from quinoxaline, the dimer formation took place in THF also, and mixtures of mono- and diiodides were obtained whatever the solvent and conditions used. A similar competitive formation of a diiodide was noted with pyridazine; the use of THF at reflux temperature nevertheless afforded the 3-iodo derivative in good yield.

Synthesis and characterization of new tungstosilicate aggregates assembled with a mixture of mono- and trivacant Keggin fragments

The reaction mixture of two lacunary Keggin-type polytungstosilicates K 8[α-SiW 11O 39] and Na 9[A- β-SiW 9O 34H] in aqueous solution with different pH values led to the isolation of two new aggregates K 4Na 11Li 5[Si 3W 26O 94] · ∼21H 2O ( 1) and K 5Na 11[Si 2W 19O 69(H 2O)] · ∼22H 2O ( 2). Single crystal X-ray diffraction analyses reveal that the polyoxoanion of 1 consists of two {B-α-SiW 9O 34} trivacant Keggin units and one B-type hexavacant {B-SiW 6O 26} fragment which are connected by two disordered {WO 6} octahedra to form a C-shaped aggregate. Compound 2 is composed of two {A-α-SiW 9O 34} building blocks linked by a {WO(H 2O)} segment. These two structural topologies are firstly observed in polytungstosilicate family and their possible assembly routes are speculated.

Sunscreen immobilization on ZnAl-hydrotalcite for new cosmetic formulations

Abstract Intercalation compounds of ZnAl-hydrotalcite with the UV absorber 5-benzoyl-4-hydroxy-2-methoxy-benzenesulphonate acid (4BHF) have been prepared by ion exchange procedure and used to obtain sunscreen stabilization for new cosmetic formulations. Compounds having a sunscreen loading from 26% to 38% w/w have been obtained changing the pH of the equilibrating solution. In fact, taking advantage of the bi-protic nature of 4BHF, the mono-anions, the di-anions or a mixture of mono- and di-valent anions have been intercalated into the hydrotalcite. The compounds obtained have been firstly characterized by TG, XRPD, DSC, and SEM techniques, and then dispersed in a suitable waterproof silicon cream to obtain new sunscreen formulations. The in vitro 4BHF release from the formulation has been determined. Furthermore, the intercalation products and their formulations have been investigated by means UV–vis absorption spectroscopy in order to study the matrix influence on sunscreen sunlight protection effect and on their photostability. The 4BHF intercalation between ZnAl-hydrotalcite lamellae can be considered a good strategy to increase the sunscreen stability and to prepare solar cosmetic formulations always more efficacious and safe.

Synthesis and structural characterization of P2O5–CaO–Na2O sol–gel materials

Ternary phosphate-based glasses in the system P2O5–CaO–Na2O were synthesized using the sol–gel approach. Glasses in this system have the potential for use as bioactive materials. A mixture of mono- and dialkyl phosphate PO(OH)3−x(OC2H5)x (x=1,2) and alkoxides of sodium and calcium in an ethylene glycol solution were used as precursors. One of the compositions has also been synthesized by sonocatalysis (application of ultrasonic vibration to the sol). The systems synthesized, which remain fully amorphous even after calcination at 400°C given the appropriate composition, have been characterized using X-ray diffraction (XRD). Thermal properties have been examined by means of thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The structure of the phosphate network has been studied as a function of composition using Fourier transform infrared spectroscopy (FT-IR) and 31P MAS NMR.

Investigations of the mono- and dicycloaddition reactions of [SNS][MF6] (M = As, Sb) with the dinitriles NCC(O)CN and NCC(Cl)2CN — Energetics and the preference for [SNS]+dicycloaddition products in solution and solid state

The stepwise symmetry-allowed cycloaddition reactions of [SNS]+with the dinitriles NC–X–CN (X = CCl2, CO) were investigated. The reaction of [SNS]+and dinitrile in 2:1 ratio yielded the dicycloaddition product quantitatively after 2 weeks (in situ13C NMR). At a 1:1 ratio, mixtures of mono- and dicycloaddition products were obtained that could not be completely separated from one another. The energetics of the reaction were estimated in the gas phase, in solution (SO2and CH2Cl2), and solid phases using DFT calculations (PBE0/6-311G*) and a "volume-based thermodynamics" approach for lattice enthalpies. Monocycloaddition products are stable in the gas phase and in solution with respect to disproportionation reactions, but in the solid state the disproportionation of 2 [NC–X–(CNSNS)][AsF6] into [X(CNSNS)2][AsF6]2and NC–X–CN is strongly favored because of the higher lattice enthalpy of the 1:2 salt. In the gas phase, the second cycloaddition is endothermic because of the charge repulsion of the two positive charges, but in the solid state the reaction is strongly favored because of the lattice enthalpy gain on the formation of the 1:2 ([X(CNSNS)2][AsF6]2) from two 1:1 salts ([NC–X–(CNSNS)][AsF6] and [SNS][MF6]). The crystal structures of the dicycloaddition products [Cl2C(CNSNS)2][AsF6]2and [OC(CNSNS)2][AsF6]2and the monocycloaddition product [Cl2C(CNSNS)CN][AsF6] were obtained. In [Cl2C(CNSNS)CN][AsF6], the free nitrile groups interact with neighboring heterocycles further demonstrating that potential of free nitrile groups for introducing intermolecular interactions. [OC(CNSNS)2]2+is a planar dication, which adopts the conformation with Sδ+···Oδ–contacts to optimize intramolecular electrostatic interactions.Key words: crystal structure, sulfur-nitrogen, 1,3,2,4-dithiadiazolyium, nitriles, cycloaddition, DFT calculations, thermodynamics, energetics.

Nanoblossoms: Light-Induced Conformational Changes of Cationic Polyelectrolyte Stars in the Presence of Multivalent Counterions

We analyze the structure of star-shaped polyelectrolytes in the presence of di- and trivalent counterions, and we use the gained knowledge to manipulate the polyelectrolyte's conformation by light. By applying dynamic light scattering and atomic force microscopy, we demonstrate that, at constant ionic strength, the arms of the cationic polyelectrolyte retract when adding multivalent counterions. Adding trivalent hexacyanocobaltate(III) ions leads to a collapse of the polyelectrolyte star even at low concentrations. This is shown by analysis of the star polyelectrolytes in solution as well as in the adsorbed state on mica surfaces. Considerably higher salt concentrations are necessary to obtain the same contraction of the polyelectrolyte star if the divalent tetracyanonickelate(II) ions are used. Sufficiently high multivalent counterion concentration leads finally to the precipitation of the polymer from the solution. We demonstrate that we can switch a polyelectrolyte star from the collapsed to the expanded state by transforming the trivalent hexacyanocobaltate(III) ions into a mixture of mono- and divalent ions by UV light. Thus, these collapsed stars react to light like "nanoblossoms". Moreover, polyelectrolyte stars precipitated through addition of the trivalent hexacyanocobaltate(III) ions can be redissolved by irradiation with light (photoinduced dissolution). Hence, the conformation and interaction of star polyelectrolytes can be switched by light. Possible applications of this novel way of manipulating polymers are discussed.

The preparation of pellets containing a surfactant or a mixture of mono- and di-gylcerides by extrusion/spheronization

The ability to incorporate either of the two components of a self-emulsifying system (polysorbate 80 (PSG80) and a mixture of mono- and di-glycerides (MDG)) separately into pellets prepared by extrusion/spheronization and the properties of any resulting pellets has been investigated. The results have established that it is possible to prepare satisfactory pellets thus adding to the range of ingredients that can be included in pellet formulations. For PS80, it was found possible to prepare pellets containing at least 92% of the surfactant/water mixture, but with a mixture of (MDG) and water, however, it was not possible to prepare pellets, which contained more than 46% of MDG. By analysis of variance significant relationships were established between the ratio of lactose to MCC and the ratio of the PS80 or MDG to water and the properties of the pellets. There were both similarities and differences of the two input factors, which provided relationships for the two materials. The quantity of liquid required, the fluid content of the pellets, the tensile strength and porosity of the pellets provided relationships for both systems, whereas the extrusion force and the median pellet size gave relationships for the PS80 systems, but they did not for the MDG systems. The opposite was true for interquartile range (IQR), the yield in the modal fraction and the shape factor. It was possible to identify global relationships for these systems and those reported previously, when the two components were combined as a self-emulsifying system, by the application of perceptual mapping. It was found that, there were relationships between the size range, expressed as the IQR and the fluid level required to make pellets; the quantity of the non-aqueous component of the fluid and the pellet shape factor; the extrusion force and the tensile strength of the pellets and the yield in the modal fraction and the ratio of the non-aqueous to aqueous content of the fluid used to prepare the pellets. The ability to use the materials independently offers further alternatives for the formulation of water insoluble drugs into pellet formulations.

An Investigation of the Leaf Oils of the Western Australian Broombush Complex (Melaleuca uncinata sens. lat.) (Myrtaceae)

The leaf oils of the 11 recorded Western Australian species of the broombush complex of the genus Melaleuca have been examined by a combination of GC and GC/MS. Melaleuca atroviridis produced a monoterpenic leaf oil with α-pinene (11.0%) and 1,8-cineole (73.2%) being the principal components. Melaleuca concreta showed the presence of three chemotypes, one of which was rich in terpinen-4-ol (35.4%), while a second was rich in 1,8-cineole (58–81%). A third chemotype contained signifcant amounts of α-pinene (16.7%), 1,8-cineole (28.4%) and globulol (11.3%). Melaleuca exuvia produced a monoterpenic oil, which appeared to exist in two chemotypes, which contained α-pinene (13–23%), 1,8-cineole (56–67%), terpinen-4-ol (0.1–2%) and α-terpineol (3–7%) in one form and α-pinene (5–7%), 1,8-cineole (28–38%), terpinen-4-ol (11–17%) and α-terpineol (3–4%) in the second form. Melaleuca hamata produced a leaf oil that was dominated by monoterpenes. There appeared to be two chemotypes present, one in which terpinen-4-ol (41.6%) was the major component and a second chemotype in which 1,8-cineole (40.0%) and linalool (33.9%) were the principal components. Melaleuca interioris (from one population) contained a mixture of mono- and sesquiterpenes, in which sesquiterpenes predominated. Melaleuca osullivanii gave a leaf oil in which sesquiterpenes predominated, the principal component being spathulenol (10–18%). Melaleuca scalena produced a leaf oil dominated by monoterpenes, with α-pinene (25–31%) and 1,8-cineole (43–55%) being the principal components. Melaleuca stereophloia was dominated by monoterpenes of which the principal component was 1,8-cineole (78–83%). Melaleuca uncinata sens. strict. existed in a variety of forms one of which had major amounts of 1,8-cineole (44–56%), while a second contained major amounts of terpinen-4-ol (21–31%), γ-terpinene (10–14%) and α-terpinene (6–8%). Melaleuca vinnula appeared to exist in two chemotypes, one of which was rich in α-pinene (65.3%), while the second chemotype was rich in 1,8-cineole (60.6%). Melaleuca zeteticorum produced a leaf oil that was overwhelmingly monoterpene in character, the principal component being 1,8-cineole (63–68%).

Photo‐differential scanning calorimetry study on photopolymerization of nanosized titanium dioxide/polyacrylate hybrid materials

AbstractNanosized titania–polyacrylate hybrid films were prepared by controlled hydrolysis of titanium tetrabutoxide (TTB) in Span 85/Tween 80 reverse micelles as well as rapid entrapment of nanosized particles by subsequent photopolymerization. This work focused on the characterization of the photopolymerization of the transparent hybrid films via photocalorimetry. The polymerization kinetics of several mixtures of mono‐ and di‐functional acrylate monomers were compared to examine the effect of average functionality. Further, Effects of [H2O]/[surfactant] molar value and TTB concentration on photopolymerization kinetics were also studied. X‐ray photoelectron spectra and FTIR demonstrated the formation of TiO2 in the hybrid films. Atomic Force Microscope (AFM) images showed the inorganic domains with mean sizes of 25 nm were uniformly dispersed in the polymeric networks. Copyright © 2006 Society of Chemical Industry

Acidity constants in methanol/water mixtures of polycarboxylic acids used in drug salt preparations: Potentiometric determination of aqueous p Ka values of quetiapine formulated as hemifumarate

The acidic dissociation constants in a number of methanol/water mixtures of mono and polycarboxylic acids commonly used in the preparation of drug salts were determined. These solvent mixtures are usually used to determine the p K a of drugs of low aqueous solubility. However, when these drugs are prepared in salt form, the acid–base equilibria of both the basic drug and the counter-anion are involved in the potentiometric titration curves. In these instances, the inclusion of the p K a of acids as constant values in the curve fitting provides easy computation of the drug p K a without the need of any previous step to get the free base. As an application example, the aqueous p K a values of the quetiapine formulated as hemifumarate (Seroquel) were estimated by extrapolation from the experimental p K a in several methanol/water mixtures, which were then calculated according to the suitable constants of fumaric acid. The estimated aqueous p K a values of quetiapine are compared with those directly obtained in aqueous solution by potentiometry and by capillary electrophoresis.

Mixtures of mono-, di- and tri-glycerides as energy supplements to broilers’ diets

Mixtures of mono-, di- and tri-glycerides from olive oil (MDT) were added to: palm oil (PO), olive oil (OO), soybean oil (SO), free fatty acids from palm oil (PFA), free fatty acids from olive oil (OFA). The compound mixtures were used as energy supplements in the diets of broiler chickens in comparison with plain SO and plain animal fat (AF). Two hundred and ten birds were randomly allotted to 7 dietary treatments with the diverse oil sources: 6 birds per cage, 5 cages per treatment. The effects of the treatments on growth rates, feed/gain ratios and acidic composition of abdominal fat of hybrid Ross 308 female chickens were studied. The animals were slaughtered at the end of the trial, at day 35. The breast meat quality was then evaluated by a panel of 15 trained members and analysed for shelf life duration. The AF treatment gave the highest weight gain, but only in the first week. MDT + OO (50/50) resulted the best combination, with slight, non significant, better performances and a decidedly better quality in terms of acidic composition of abdominal fat, taste and juiciness of breast meat and shelf life.