Development of a temperature-responsive agarose-based ion-exchange chromatographic resin

A temperature-responsive ion-exchange resin (ItBA) has been prepared by grafting poly(N-isopropylacrylamide-co-acrylic acid-co-tert-butylacrylamide; ItBA) onto cross-linked agarose. A carboxymethylated ion exchanger (CM) of similar charge density was also prepared. Maximum adsorption capacities (B_max) for lactoferrin at 20 °C and 50 °C were determined for both resins by batch adsorption procedures. Dynamic adsorption and desorption characteristics of the CM and ItBA with lactoferrin were established, as well as the ability of ItBA to selectively adsorb and desorb lactoferrin in the presence of other proteins. With the CM-agarose resin there was no significant difference between the B_max values obtained at 20 °C and 50 °C. However, for the agarose-based ItBA resin the B_max value at 50 °C was almost three times higher than the B_max value at 20 °C. Dynamically, lactoferrin adsorbed to the ItBA packed column at 50 °C with a significant proportion of the adsorbed lactoferrin desorbed by reducing the temperature to 20 °C. In addition, anionic proteins did not adsorb to the ItBA packed column, and did not interfere with the dynamic adsorption/desorption behaviour of lactoferrin. These results indicate that this new temperature-responsive agarose-based ItBA resin has potential for the fractionation of whey proteins, with good selectivity for cationic proteins.     

Molybdenum oxide/bipyridine hybrid material {[MoO3(bipy)][MoO3(H2O)]}n as catalyst for the oxidation of secondary amines to nitrones

The inorganic-organic hybrid material {[MoO₃(bipy)][MoO₃(H₂O)]}_n (bipy = 2,2′-bipyridine) can be used as a water-tolerant catalyst for the oxidation of secondary amines under mild conditions using either urea hydrogen peroxide (UHP) or tert-butylhydroperoxide (TBHP) as the oxidant. Under optimized reaction conditions (2 mol % catalyst, 3-4 equiv TBHP, CH₂Cl₂ as the solvent, 40 °C), the corresponding nitrones were obtained with different efficiency depending on the nature of the cyclic or acyclic amine used.     

PMo or PW heteropoly acids supported on MCM-41 silica nanoparticles: Characterisation and FT-IR study of the adsorption of 2-butanol

Mesoporous silica, prepared in basic conditions, has been loaded (20% weight) with 12-molybdophosphoric (PMo) or 12-tungstophosphoric (PW) acid and calcined at different temperatures ranging between 250 and 550 °C. The samples have been characterised by N₂ adsorption-desorption at −196 °C, transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), UV-visible diffuse reflectance, Raman spectroscopy and temperature programmed reduction (TPR). The acidity and catalytic activity have been, respectively, examined by monitoring the adsorption of pyridine and 2-butanol by FT-IR spectroscopy. The results indicate that PW and PMo acids are highly dispersed on mesoporous silica MCM-41 spherical nanoparticles. While PMo retains its Keggin structure up to 550 °C, PW decomposes at this temperature into crystalline WO₃ and phosphorous oxides. In both cases, the morphology, hexagonal symmetry and long-range order observed for the support are preserved with calcination up to 450 °C. The Brönsted-type acid sites found in all samples, whose surface concentration decreases as the calcination temperature increases, are responsible for the selective formation of cis-butene detected upon adsorption of 2-butanol. The sample containing PW calcined at 450 °C also shows selectivity to methyl ethyl ketone.     

Effect of fluorination: Conformation of 2,6-difluoroanisole

The geometric structure and conformation of 2,6-difluoroanisole, 2,6-C₆H₃F₂OCH₃, has been determined with gas electron diffraction (GED) and quantum chemical calculations (MP2 and B3LYP with 6-311++G(2df,pd) basis sets). The GED intensities have been analyzed with a static as well as with a dynamic model. The static model resulted in a structure with near-perpendicular orientation of the O-CH₃ bond with a thermal average dihedral angle τ(C2C1-OC) = 70 ± 3°. With the dynamic model a perpendicular equilibrium structure and a potential function for internal rotation around the C-O bond with a very flat minimum at τ(C2C1-OC) = 90° and with a barrier of 1.8 ± 0.6 kcal/mol at τ(C2C1-OC) = 0° was derived. Quantum chemical calculations predict double-minimum potential functions for the electronic energies, which become single-minimum potentials upon addition of zero-point vibrational energies. The change of conformation from planar in anisole to perpendicular in 2,6-difluoroanisole has been rationalized by orbital interactions between the oxygen electron lone pairs and benzene ring orbitals and by steric repulsion.     

N-Hydroxyphthalimide in combination with Cu(II), Co(II) or Mn(II) salts as catalytic systems for the oxidation of isopropyl-aromatic hydrocarbons with oxygen

Catalytic systems consisting of N-hydroxyphthalimide in combination with copper(II), cobalt(II) and manganese(II) acetylacetonate, acetate or chloride were applied to the oxidation of cumene with oxygen. The use of these catalytic systems decreases cumyl hydroperoxide selectivity as a result of the decomposition reaction of hydroperoxide to 2-phenyl-2-propanol and acetophenone. It has been demonstrated that the use of N-hydroxyphthalimide in combination with copper salts at 60 °C results in high alcohol content whereas ketone is the major product at 90 °C. The results can be used to develop a method for alcohol or ketone synthesis from other isopropyl-aromatic hydrocarbons.     

Intramolecular 1,3-dipolar cycloaddition of unsaturated nitrones derived from methyl α-d-glucopyranoside

The intramolecular 1,3-dipolar cycloaddition of unsaturated nitrones derived from methyl α-d-glucopyranoside with 2-furaldehyde has been studied. This cycloaddition was found to afford three 9-oxa-1-azabicyclo[4.2.1]nonane diastereomers in a 3:1:1 ratio [with the principal isomer possessing a (3S,4R,5S,6S,8S) configuration, determined by NMR spectroscopy]. The effects of different Lewis acid catalysts (MgCl₂, ZnCl₂ and BF₃·OEt₂) on yields and diastereomeric ratios have been examined in detail. The best result (90% yield) was achieved when MgCl₂ was present (in toluene, 120 °C bath temperature, 12 h). The stereoselectivity of the 1,3-dipolar cycloaddition was not significantly altered under the conditions investigated.     

Electron-beam irradiation on poly(propylene carbonate) in the presence of polyfunctional monomers

Poly(propylene carbonate) (PPC) showed predominantly degradation under electron-beam irradiation, accompanied by deterioration of its mechanical performance due to sharp decrease of the molecular weight. Crosslinked PPC was prepared by addition of polyfunctional monomer (PFM) to enhance the mechanical performance of PPC. When 8 wt% of PFM like triallyl isocyanurate (TAIC) was added, crosslinked PPC with a gel fraction of 60.7% was prepared at 50 kGy irradiation dose, which showed a tensile strength at 20 °C of 45.5 MPa, whereas it was only 38.5 MPa for pure PPC. The onset degradation temperature (T_i) and glass transition temperature (T_g) of this crosslinked PPC was 246 °C and 45 °C, respectively, a significant increase related to pure PPC of 211 °C and 36 °C. Therefore, thermal and mechanical performances of PPC could be improved via electron-beam irradiation in the presence of suitable PFM.     

Bio-oil production from Onopordum acanthium L. by slow pyrolysis

In this study, the usability of the plant thistle, Onopordum acanthium L., belonging to the family Asteraceae (Compositae), in liquid fuel production has been investigated. The experiments were performed in a fixed-bed Heinze pyrolysis reactor to investigate the effects of heating rate, pyrolysis temperature and sepiolite percentage on the pyrolysis product yields and chemical compositions. Experiments were carried out in a static atmosphere with a heating rate of 7 °C/min and 40 °C/min, pyrolysis temperature of 350, 400, 500, 550 and 700 °C and particle size of 0.6 < D_p < 0.85 mm. Catalyst experiments were conducted in a static atmosphere with a heating rate of 40 °C/min, pyrolysis temperature of 550 °C and particle size of 0.6 < D_p < 0.85 mm. Bio-oil yield increased from 18.5% to 27.3% with the presence of 10% of sepiolite catalyst at pyrolysis temperature of 550 °C, with a heating rate of 40 °C/min, and particle size of 0.6 < D_p < 0.85 mm. It means that the yield of bio-oil was increased at around 48.0% after the catalyst added. Chromatographic and spectroscopic studies on the bio-oil showed that the oil obtained from O. acanthium L. could be used as a renewable fuels and chemical feedstock.     

A novel thermal rearrangement of allenic imidothioates. Formation of iminocyclobutenes

Allenic imidothioates, H₂CCC(Ph)C(SMe)NR (R = Me, t-Bu, Ph) have been obtained in good yields by reaction of 1,3-dilithiated 1-(2-propynyl)benzene with isothiocyanates and successive addition of t-butyl alcohol and methyl iodide. Heating the imidothioates at ∼120 °C gave an iminocyclobutene as the only isolated product (if R = t-Bu), a ∼4:6 mixture of a 2,3-dihydropyridine and an iminocyclobutene (if R = Me) or a 3:1 mixture of a quinoline and an iminocyclobutene (if R = Ph).     

Bovine serum albumin recognition via thermosensitive molecular imprinted macroporous hydrogels prepared at two different temperatures

A novel temperature-sensitive molecular imprinted hydrogel composed of 2-acrylamido-2-methyl-propanosulfonic acid (AMPS), N-isopropylacrylamide (NIPAm) and acrylamide (AAm) has been prepared by free-radical cross-linking copolymerization in aqueous solution under two different temperatures (25 °C and −20 °C). Bovine serum albumin (BSA, pI 4.9, MW 66.0 kDa) is used as the template protein. The influence of the external temperature stimuli on the affinity of the hydrogels was investigated, and the optimal binding conditions were tested. The adsorption capacity (Q_max) and association constant (K) for the specific interaction between the hydrogel and the template protein were determined by Langmuir isotherm plots. Several types of reference protein, which are different in molecular weights and isoelectric points were chosen to investigate the selectivity of the hydrogels. It was shown that the shape memory and the charge effect were the major factors for the recognition. This imprinted hydrogel was used to specifically adsorb the BSA from the protein mixture and real sample, which demonstrated its potential selectivity.     

Direct hydroxylation of substituted benzenes to phenols with air and CO using molybdovanadophosphates as a key catalyst

A direct synthetic method of cresols from toluene by hydroxylation with air using CO as a reducing agent was developed. The reaction of toluene with air (15 atm) and CO (5 atm) in the presence of catalytic amounts of H₄PMo₁₁VO₄₀·31H₂O and Pd/C in aqueous acetic acid at 120 °C for 2 h afforded a mixture of o-, m-, and p-cresols in 9.9% yield at 83% selectivity. Cresols were obtained in 19% yield by recharging air and CO under these conditions. A variety of substituted benzenes were hydroxylated by this method to give the corresponding phenol derivatives in higher selectivity.     

Kinetics of reduction of iron oxides by H2: Part II. Low temperature reduction of magnetite

This study deals with the reduction of Fe₃O₄ by H₂ in the temperature range of 210-950 °C. Two samples of Fe₃O₄ produced at 600 and 1200 °C, designated as Fe₃O₄₍₆₀₀₎ and Fe₃O_4(1200), have been used as starting material.Reduction of Fe₃O₄₍₆₀₀₎ by H₂ is characterized by an apparent activation energy ‘E_a’ of 200, 71 and 44 kJ/mol at T < 250 °C, 250 °C < T < 390 °C and T > 390 °C, respectively. The important change of E_a at 250 °C could be attributed to the removal of hydroxyl group and/or point defects of magnetite. This is confirmed during the reduction of Fe₃O_4(1200). While transition at T ≈ 390 °C is probably due to sintering of the reaction products as revealed by SEM.In situ X-rays diffraction reduction experiments confirm the formation of stoichiometric FeO between 390 and 570 °C. At higher temperatures, non-stoichiometric wüstite is the intermediate product of the reduction of Fe₃O₄ to Fe.The physical and chemical modifications of the reduction products at about 400 °C, had been confirmed by the reduction of Fe₃O₄₍₆₀₀₎ by CO and that of Fe₃O_4(1200) by H₂. A minimum reaction rate had been observed during the reduction of Fe₃O_4(1200) at about 760 °C. Mathematical modeling of experimental data suggests that the reaction rate is controlled by diffusion and SEM observations confirm the sintering of the reaction products.Finally, one may underline that the rate of reduction of Fe₃O₄ with H₂ is systematically higher than that obtained by CO in the explored temperature range.     

Complex formation equilibria between Ag(I) and thioureas in n-propanol

Complex formation equilibria between Ag(I) and thiourea or N-alkyl-substituted thioureas have been investigated in n-propanol by potentiometry at 10 °C intervals from 5 to 50 °C. Stepwise formation of tris-coordinated AgL_n (n = 1-3) complexes has been found for the majority of the ligands. ΔH and ΔS values for the complex formation reactions have been evaluated from the dependence of ln β_n on temperature. The alkyl-substituents affect the ligand affinities in different ways in relation with the coordination level n.The reactions are exothermic with few exceptions. Enthalpy favoured complex formation with negative dependence of ΔG on temperature (ΔS > 0) have been found.The enthalpy and entropy changes for the stepwise complex formation equilibria are correlated by two linear compensative relationships with the same isoequilibrium temperature 50-51 °C.     

Thermodynamics of interactions between organic ammonium ions and sulfonatocalixarenes

Calorimetric titration and NMR experiments in aqueous phosphate buffer (pH 7.2) at 298.15 K have been done to determine the binding mode, complex stability constants and thermodynamics (ΔG°, ΔH°, and TΔS°) for 1:1 inclusion complexation of water-soluble calix[n]arenesulfonates (CnAS, n = 4 and 6) and thiacalix[4]arene tetrasulfonate (TCAS) with acethylcholine, carnitine, betaine and benzyltrimethylammonium ion. The results show the inclusion complexations are driven by enthalpy (ΔH° < 0), accompanied by negative entropic changes (ΔS° < 0). The binding affinities (C4AS > C6AS > TCAS) are discussed from the viewpoint of CH-π/π-π interactions, electrostatic interactions and size/shape-fit relationship between host and guest.     

Remarkable effect of hydrogen-bonding interaction on stereospecificity in the radical polymerization of N-vinylacetamide

Radical polymerization of N-vinylacetamide (NVA) in toluene at low temperatures was investigated. It was found that the addition of Lewis bases or alcohol compounds significantly influenced stereospecificity in NVA polymerization. For example, syndiotacticity increased from 25% to 34% by adding tri-n-butyl phosphate at −40 °C. Mono-alcohol compounds increased heterotacticity and heterotactic poly(NVA) with mr triad content of 58% was obtained at −40 °C in the presence of 1,1,1,3,3,3-hexafluoro-2-propanol. Furthermore, isotactic poly(NVA) with mm triad = 49% was obtained at −60 °C in the presence of diethyl l-tartrate. The NMR analysis demonstrated that complex formation between NVA monomer and the added agents, through hydrogen-bonding interaction, played an important role to induce the stereospecificity.     

High temperature liquid chromatography of intact proteins using organic polymer monoliths and alternative solvent systems

Alternative approaches to conventional acetonitrile gradient methods for reversed-phase liquid chromatographic analysis of intact proteins have been investigated using commercial poly(styrene-co-divinylbenzene) monolithic columns (Dionex ProSwift™ RP-2H and RP-4H). Alternative solvents to acetonitrile (2-propanol and methanol) coupled with elevated temperatures demonstrated complementary approaches to adjusting separation selectivity and reducing organic solvent consumption. Measurements of peak area at increasing isothermal temperature intervals indicated that only minor (<5%) decreases in detectable protein recovery occurred between 40 and 100 °C on the timescale of separation (2–5 min). The reduced viscosity of a 2-propanol/water eluent at elevated temperatures permitted coupling of three columns to increase peak production (peaks/min) by 16.5%. Finally, narrow-bore (1 mm i.d.) columns were found to provide a more suitable avenue to fast, high temperature (up to 140 °C) separations.     

Thin Pd–23%Ag/stainless steel composite membranes: Long-term stability,life-time estimation and post-process characterisation

The long-term stability of Pd–23%Ag/stainless steel composite membranes has been examined in H₂/N₂ mixtures as a function of both temperature and feed pressure. During continuous operation, the membrane shows a good stability at 400 °C while the N₂ leakage increases very slowly at a temperature of 450 °C (P_feed = 10 bar). After 100 days of operation (P_feed = 5–20 bar, T = 350–450 °C), the N₂ permeance equals 7.0 × 10⁻⁹ mol m⁻² s⁻¹ Pa⁻¹, which indicates that the H₂/N₂ permselectivity still lies around 500, based on a H₂ permeance equal to 3.0 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹. Despite the generation of small pinholes, a membrane life-time of several (2–3) years (T ≤ 425 °C) is estimated for the experimental conditions employed based on long-term stability tests over 100 days. Post-process characterisation shows a considerable grain growth and micro-strain relaxation in the Pd–23%Ag membrane after the prolonged permeation experiment. Changes in surface area are relatively small. In addition, segregation of Ag to the membrane surfaces is observed. The formation of pinholes is identified as the main source for the increased N₂ leakage during testing at higher temperature.     

Cyanoesterification of norbornenes catalyzed by palladium: facile synthetic methodology to introduce cyano and ester functionalities via direct carbon-carbon bond cleavage of cyanoformates

Addition of cyanoformates (NC-COOR) to norbornene at 110 °C in the presence of Pd(PPh₃)₄ (10 mol %) as a catalyst affords with high selectivity the corresponding doubly functionalized polar norbornane derivatives bearing both cyano and ester groups. By using benzonorbornadiene and norbornadienes as the substrates, the reaction can be extended to synthesis of various functionalized norbornene derivatives in moderate to excellent yields. In most cases alkyl groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl, and benzyl in the ester functionalities are applicable to the reactions. Oxidative addition of cyanoformates to Pd(0), insertion of norbornenes, and reductive elimination of the corresponding adducts constitute the proposed catalysis pathway.     

New efficient organocatalytic oxidation of benzylic compounds by molecular oxygen under mild conditions

Efficient aerobic oxidation of benzylic compounds has been achieved under no irradiation using a new organocatalytic system in the presence of acridine yellow and N-hydroxyphthalimide with assistance of a catalytic amount of molecular bromine. Various substrates, especially alkylaromatics, were effectively oxygenated to the corresponding carbonyl compounds with molecular oxygen as oxidant under mild conditions. For instance, indan was oxidized with 92% conversion and 79% selectivity for 1-indanone under 0.3 MPa of O₂ at 75 °C.     

Albumin molecularly imprinted polymer with high template affinity — Prepared by systematic optimization in mixed organic/aqueous media

An approach using systematic optimization for the formation of an albumin molecularly imprinted polymer (MIP), able to separate albumin from proteins in solution, has been prepared by imprinting albumin using a copolymer comprising 3-dimethylaminopropyl methacrylate and tetraethylene glycol dimethacrylate in a mole ratio of 1 to 8. Cytochrome c, lysozyme and myoglobin were used in competitive re-binding experiments to compete with the polymer's native template with all protein species present at 0.0004 g mL^− 1. The effects of: monomer to crosslinker mole ratio, polymerization temperature and time were investigated. It was found that the addition of water 6.04%, into the pre-polymerization albumin-monomer complex enhanced the adsorption capacity and selectivity of the resulting MIP from 2.18 × 10^− 3 to 6.02 × 10^− 3 g g-MIP^− 1 and 83.5% to 98.7%, respectively. These results also showed that the MIP possessed high selectivity and adsorption capacity with respect to albumin in comparison with interfering species also present in solution. Polymerization temperature, time and the water content of the pre-polymerization mixture were all shown to have significant effects on the resulting albumin-MIP's performance. However, their influence on the polymer's affinity for the potentially interfering species was negligible. Additionally, higher polymerization temperatures (> 38 °C) and extended polymerization times (> 60 h) increased monomer conversion as determined by HPLC, but decreased the selectivity and adsorption capacity of the MIP. An optimized MIP, with very high selectivity and 6.37 × 10^− 3 g g-MIP^− 1 template re-adsorption capacity was obtained using the following polymerization conditions: 0.125 mole ratio of monomer to crosslinker, 6.04 wt.% water content with respect to the mass of the monomer complex, 60 h polymerization time at 38 °C, and with 0.47% albumin in the pre-polymerization monomer complex. Finally, the functions of polymerization temperature, time and the significance of the water content in the albumin-monomer complex are also discussed.