The chemistry and biology of β-thiolactones

The structure and properties of β-thiolactones (2-thietanones) are discussed with an emphasis on the differences with β-lactones. Methods for the synthesis of β-thiolactones are reviewed as are the reactions of this relatively little explored class of sulfur-based hetereocycles. Finally, the biology of β-thiolactones is reviewed.     

Synthesis and hydrolysis of β-cyanoethyl ether of poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) was cyanoethylated by reaction with acrylonitrile in the presence of sodium hydroxide and quaternary ammonium halide. Quaternary ammonium halide, acting as a phase transfer catalyst, increases the degree of substitution (DS) of PVA. The DS also increased with increasing acrylonitrile concentration. Cyanoethylation of PVA up to 98% can be achieved under optimum conditions. The hydrolysis of β-cyanoethyl ether of PVA (CN–PVA) was studied. The rate of hydrolysis was affected by the sodium hydroxide concentration and the reaction temperature. The rheological properties of aqueous solution of hydrolysis product of CN–PVA were determined at different temperatures, and the flow activation energy was calculated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2771–2777, 1999     

Optimal preparation of β-cyclodextrin microsphere using uniform design

为了优化β-环糊精微球的制备工艺,采用U₁₃*（13⁴）均匀设计对合成工艺优化,得出最佳合成工艺为反应温度80 ℃,反应时间4 h,交联剂的用量8 g,搅拌速度1000 r/min。影响微球粒径的因素：搅拌速度>反应温度。影响产量的因素：交联剂的用量>反应时间。最佳合成工艺下的微球表面圆整,具有较好的热稳定性。     

The hydrolysis process of γ-AlON powder and preparation of highly transparent ceramics with aqueous gel-casting

The untreated γ-AlON powders were proposed to prepare highly transparent γ-AlON ceramics by aqueous gel-casting technique and two-step sintering process. The related mechanism of hydrolysis of γ-AlON powders was discussed. The surface of the synthesized γ-AlON powders is covered with a layer of aluminum hydroxides compound. As the period of hydrolysis extends, the surface layer dissolved, and the boehmite and bayerite gradually formed, which is characterized by various techniques including XRD, FT-IR, XPS and TEM. The low viscosity slurry with high solids loading (53 vol%) was obtained by γ-AlON powders without any surface modification treatments as a result of the slow hydrolysis process. In addition, compared with the dry pressed sample, the sample (4.12 mm in thickness) prepared by aqueous gel-casting exhibits superior in-line transmittance of 81–83% in the visible region, which could be ascribed to the more homogenous and denser microstructure of the green body. Finally, the Weibull modulus and characteristic strength of γ-AlON transparent ceramic were determined to be 4.85 and 295 MPa, respectively.     

The preparation and characterization of HA/β-TCP biphasic ceramics from fish bones

The aim of this research is to observe the physicochemical characterization and evaluate the biocompatibility of the HA/β-TCP biphasic calcium phosphate ceramics (BCP) produced from fish bones. In addition, the mechanism of the formation of BCP after calcination of fish bones was discussed. Three kinds of fish bones (Salmo salar, Anoplopoma fimbria and Sardine) were prepared and calcined for one hour at different temperatures ranging from 600 °C to 1100 °C in a muffle furnace. The calcined bones were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (GTA), inductively coupled plasma optical atom emissions spectroscopy (ICP-OES), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). The in vitro cytotoxicity assessment was used to evaluate the biocompatibility of the biphasic ceramics. BCP materials were produced from all kinds of fish bones by calcination above 700 °C, the carbonated hydroxyapatite and multiple trace element were also found in the calcined bones. With the increase of temperature, the ratio of HA/β-TCP varied and the major organic components were progressively removed. The carbonated hydroxyapatite disappeared when temperature rises above 900 °C. Rising temperature also caused crystal growth that eventually gave rise to the increase of the BCP grain size and influenced the mesoporous structure. The BCP materials were confirmed to have no obvious cytotoxicity to mesenchymal stem cells (MSC) in the in vitro cytotoxicity assessment. Calcium-deficient hydroxyapatite(CDHA) may make up the major inorganic constituent of fish bones that could decompose to HA and β-TCP when calcined above 700 °C. 800–900 °C is considered to be the optimal temperature to fabricate BCP materials which contain more β-TCP, carbonated hydroxyapatite and retain distinct mesoporous structure while has good biocompatibility. With the unique composition and structure, these three kinds of fish-bone-derived BCP materials can be further applied to fabricate bioceramic scaffolds for biomedical applications.     

Inclusion complexes of eucalyptus essential oil with β-cyclodextrin: preparation,characterization and controlled release

In this study, eucalyptus essential oil (EEO) was encapsulated into β-cyclodextrin (β-CD) by saturated aqueous solution method. The success of EEO encapsulation was confirmed by laser light scatting, scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimeter and thermogravimetric analysis. Releasing characteristics experiments were carried out at various temperatures, relative humidity (RH), storage time and high temperature stability test. Release kinetics of EEO from the inclusion complexes was investigated by zero-order kinetics, first-order kinetics and Avrami’s equation. The result showed that the release model of EEO from inclusion complexes fitted better for Avrami’s equation. Kinetics analysis based on the Avrami’s equation revealed that the release of EEO was accelerated with the increases of RH and temperature. For storage time treatment, the volatilization of EEO was significantly inhibited after encapsulation. High temperature stability test further revealed that EEO was protected after having been encapsulated into β-CD. For all treatments, the release parameter n was between 0.5 and 1.0, which presenting a diffusion-limited and first-order mode. These results indicated that encapsulation enhanced the stability and prolonged the acting time of EEO, and the release rate of EEO can also be passively controlled by the ambient temperature, humidity and storage time.     

Synthesis of β-SiAlON whiskers: dependence of uniform morphology upon preparation conditions

Abstract

Abstract

β-SiAlON whiskers with uniform morphology were prepared using reaction sintering method under different conditions. The effect of preparing conditions on the morphology of β-SiAlON whiskers was systematically studied by SEM, XRD, TEM and HRTEM. The results showed that single crystalline β-SiAlON whiskers with uniform morphology were successfully fabricated at 1773 K for 6 h under flowing nitrogen atmosphere. The well synthesised whiskers were of several hundreds of nanometres in diameter and a few hundreds of micrometres in length. Although the morphology and its size distribution are mainly determined by the reaction temperature and holding time, they can also be tailored by controlling the reaction atmosphere. The ratio of staring materials has no significant influence on the morphology of β-SiAlON whiskers. The growth of β-SiAlON whiskers follows a vapour–solid mechanism, and the formation of the belt-like whiskers is attributed to an anisotropic growth at the early nucleation/growth stage.     

The effect of CaO on the physicochemical and biological properties of β-SiAlON ceramics

To investigate the effects of CaO on the physicochemical and biological properties of β-SiAlON, β-SiAlON ceramics containing CaO were prepared using the direct nitriding method. The results of X-ray powder diffraction and scanning electron microscopy demonstrated that β-SiAlON remained in the material phase because the addition of Ca did not result in the formation of Ca-α-SiAlON. However, CaO promoted the sintering of β-SiAlON grains and significantly decreased porosity and increased bulk density and compressive strength. According to a chemical stability study, when β-SiAlON ceramics powder was soaked in deionized water and a cell culture medium, it was noted to have negative electricity. A reaction occurred with the H⁺ and OH⁻ ions in the deionized water, leading to the formation of surface structures, such as Si-OH, Al-OH, and N-H. Moreover, the addition of CaO caused a different chemical reaction among ions or ion groups in the culture medium, and new chemical groups formed on the material surface that interacted with the culture medium, which resulted in an alteration of the zeta potential and surface chemical properties of β-SiAlON. MC3T3-E1 cells cultured on the surface of ceramics proved that the cells cannot adhere well to the surface of β-SiAlON ceramics with CaO, although they could proliferate well around those with only β-SiAlON. Therefore, the change in the surface chemical properties provides good anticell adhesion ability, which makes β-SiAlON with CaO a biocompatible material that can be used to prevent contamination caused by cell adhesion, with possible applications in biosensors or biomedical equipment that must be used in sterile environments.     

The Phase Behavior of γ-Oryzanol and β-Sitosterol in Edible Oil

The phase behavior of binary mixtures of γ‐oryzanol and β‐sitosterol and ternary mixtures of γ‐oryzanol and β‐sitosterol in sunflower oil was studied. Binary mixtures of γ‐oryzanol and β‐sitosterol show double‐eutectic behavior. Complex phase behavior with two intermediate mixed solid phases was derived from differential scanning calorimetry (DSC) and small‐angle X‐ray scattering (SAXS) data, in which a compound that consists of γ‐oryzanol and β‐sitosterol molecules at a specific ratio can be formed. SAXS shows that the organization of γ‐oryzanol and β‐sitosterol in the mixed phases is different from the structure of tubules in ternary systems. Ternary mixtures including sunflower oil do not show a sudden structural transition from the compound to a tubule, but a gradual transition occurs as γ‐oryzanol and β‐sitosterol are diluted in edible oil. The same behavior is observed when melting binary mixtures of γ‐oryzanol and β‐sitosterol at higher temperatures. This indicates the feasibility of having an organogelling agent in dynamic exchange between solid and liquid phase, which is an essential feature of triglyceride networks.     

Kinetics and mechanism of the preparation of Raney® copper

Raney® copper is an active hydrogenation catalyst formed by the selective dissolution of aluminium from a Cu–Al alloy. The structure of Raney® copper is presented in a series of images taken using a focussed ion beam miller (FIB). The images show a structure consisting of a uniform three-dimensional network of fine copper ligaments. A rotating disc electrode, used to control the diffusion layer, enabled a study of the kinetics of the leaching reaction at 269–303K in 2–8m NaOH. Under these conditions, the reaction rate was constant and independent of hydroxide concentration. The activation energy for leaching was determined as 69±7kJmol^–1. The mixed corrosion potential of the dissolving alloy has been related to the exposed copper surface area, which in turn is dependent on the leaching rate and the mechanism of rearrangement. The overall mechanism of formation/rearrangement of the Raney® copper structure was found to be mainly dissolution/redeposition of copper atoms, with surface or volume diffusion, or possibly both, playing a minor role.     

The effect of soluble β-nucleator's content on crystalline structure and performance of polypropylene pipe

Strength-toughness clash of polypropylene (PP) pipe is an insurmountable bottleneck for the potential application. Here, we successfully prepared PP pipe with simultaneously enhanced toughness and hoop strength via addition of soluble β-nucleators (β-NAs) and application of helical flow in the extrusion. The outstanding combination of strength and toughness in the PP pipe depended on the loading content of β-NAs and the helical pattern, which determined the morphology and alignment of β-crystals. At the low content, β-NAs dissolved completely into the PP melts and distributed homogeneously to promote the formation of β-spherulites in the PP pipe. When the loading content exceeded the solubility limit, the β-NAs partially dissolved and upon cooling, the dissolved β-NAs grew preferentially on the undissolved ones along one direction, assembling into the fibrous aggregates. With the guidance of helical flow, the fibrous β-NAs aligned off the axis and functioned as an oriented template to trigger the PP crystallization on the surface into hybrid β-shish-kebab with fibrous β-NAs as shish. Increasing rotation speed of mandrel and die elevated hoop contribution to obtain the β-shish-kebab with a deviated angle of 55°, endowing the prepared pipe with high hoop strength and toughness.     

The effect of Ag nanoparticles content on dielectric and microwave absorption properties of β-SiC

In the present work, high purity cubic silicon carbide (β-SiC) was synthesized by using resorcinol-formaldehyde aerogel coated silica as precursor at high temperature. Subsequently, β-SiC was coated with various concentrations of silver nanoparticles (Ag NPs) by tin sensitization electroless plating. Thereafter, the effect of various Ag NPs contents on the dielectric and microwave absorption properties of β-SiC was investigated in detailed. It is found that the Ag NPs can significantly increase the overall complex permittivity, reduce the thickness of the absorber and increase the absorption bandwidth to some extent. Despite, the improvement of the attenuation ability of electromagnetic wave with increasing contents of Ag NPs also has an adverse effect on impedance matching. The improvement in the microwave absorption of β-SiC coated with Ag NPs mainly comes from the enhancement of dipole polarization, interface polarization and conductivity loss. In the 2–18 GHz band, Ag@SiC (1.0 g/L) can achieve an effective bandwidth of 4.99 GHz at a thickness of 1.6 mm, and it is a kind of lightweight, high-temperature microwave absorbent with excellent performance.     

Development of diamondoids（Ⅱ）preparation and applications

金刚烃是由多个环己烷构成的饱和笼状烃,此类有机化合物的分子式为C_4n+6H_4n+12。金刚烷则是最小的金刚烃化合物（即n=1时）,其C原子骨架类似于金刚石的一个晶格单元。本文对金刚烃类化合物的制备方法和应用前景进行了评述。迄今已公开的金刚烃制备方法包括化学合成法和从天然原油中分离提纯两种方法,化学合成法是目前这一领域的研究重点。由于其独特的笼状结构和特殊的化学、物理和药理学性质,金刚烃在医药、精细化学品、航空燃料、功能材料以及纳米技术等方面具有潜在应用前景。金刚烃化学有可能成为未来有机化学领域的重要分支学科。     

Study of catalytic activity of a polymer-supported Ce catalyst for the synthesis of biofuels and β-amino alcohol derivatives under ambient condition

A novel mesoporous cerium-incorporated anthranilic acid binded chloromethylated polystyrene (PS-AN-Ce) has been developed by functionalization of chloromethylated polystyrene with anthranilic acid in DMF medium, followed by grafting of cerium on its surface using CeCl₃·7H₂O. The synthesized PS-AN-Ce has been characterized by FESEM, EDAX, AAS, FTIR, UV–Vis, TGA, and N₂ adsorption–desorption isotherm. The synthesized material is stable up to 376 °C and the Brunauer–Emmett–Teller (BET) surface area is 40.12 m² g⁻¹. PS-AN-Ce showed excellent catalytic effectiveness with high conversion rate and high TOF in the synthesis of β-amino alcohol derivatives and esterification of fatty acids in a short reaction time. In addition, the synthesized catalyst is easy to remove from the reaction mixture by centrifugation as it is a heterogeneous catalyst in origin and can be reused up to six times without any major loss of its catalytic activity. Also leaching limit of the synthesized catalyst is studied in different reaction cycle which implies that leaching of cerium from its polymeric support is negligible to consider. The extremely dispersed and sturdily bound Ce sites in the Ce-incorporated mesoporous polymer could be responsible for the observed high catalytic activities. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47650.     

The preparation and properties of zirconia-doped Y–Si–Al–O–N oxynitride glasses and glass-ceramics

Two series (N-9 and N-18 series) of zirconia-doped Y–Si–Al–O–N oxynitride glasses and glass-ceramics were designed. Nominal compositions of the glass samples in equivalent percent (eq%) are xZr: (24–0.25x)Y: (15–0.25x)Al: (61–0.5x)Si: 91O: 9 N and xZr: (24–0.25x)Y: (15–0.25x)Al: (61–0.5x)Si: 82O: 18 N (x=0, 2, 4, 6), respectively. The obtained samples were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Densities, Vickers hardness, fracture toughness, glass transition temperature, and thermal expansion coefficient data were established for each sample. Effect of Zr and N content on glass network structure, thermal and mechanical properties was investigated. It was found that the addition of zirconia is effective in preparing Y–Si–Al–O–N oxynitride glasses with lower glass transition temperature and higher hardness.     

The chemistry of α, β-unsaturated sulfoxides and sulfones: an update

A comprehensive review of recent chemistry of α, β-unsaturated sulfoxides and sulfones is presented. Emphasis has been placed on new reactions and strategies, stereo- and enantio-selective reactions, and emerging areas of interest such as metal-mediated asymmetric synthesis, solid-phase organic synthesis (SPOS), and cascade or ‘Domino’ reactions.     

A simplified method for the preparation of α- and β-eleostearic acids and a revised spectrophotometric procedure for their determination

Summary Simplified methods for the preparation of pure α- and β-eleostearic acids are described. These procedures involve saponification of α- and β-tung oils under mild conditions, followed by direct crystallization of the liberated acids at −20°C. from ethanolic solution. Only one recrystallization from ethanolic solution at +5°C. was required to produce the pure acids. Absorptivities obtained from measurements of the ultraviolet absorption revealed α-eleostearic acids of from 3–4% higher purity than those used in obtaining the equations previously recommended for the simultaneous determination of α- and β-eleostearic acids. This has necessitated a revision of these equations. Equations for the determination of each isomer from both cyclohexane and ethanol are reported. Equations are also given for an independent determination of total eleostearic acid, and for the determination of one isomer in the absence of the other. Infrared absorption spectra in the rock salt region from 2–15 microns have been measured from potassium bromide discs. These solid-state or crystalline spectra reveal, in addition to the prominent bands assigned to characteristic groupings of the eleostearic acid molecule, the progression bands by means of which carbon chain length can be computed. Presented at the 30th Fall Meeting of the American Oil Chemists' Society, Chicago, Ill., September 24–26, 1956. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Synthesis and characterization of new alkaline earth metal β-ketoiminates. The first structurally characterized strontium β-ketoiminate

The β-ketoimine MeC(O)CHCMeNH(CH₂CH₂NⁱPr₂) (HL^iPr) was prepared and used for the synthesis of new calcium, strontium and barium β-ketoiminates. These were characterized by elemental analysis, FT-IR, ¹H NMR, and, for the strontium bis-N,N-di(isopropyl)aminoethylamino-2-penten-4-onate, by single-crystal X-ray diffraction. Two molecular units having similar conformations are present in the asymmetric unit cell. Both molecules are linear trimers with six-coordinate strontium atoms and bond lengths spreading over the range 2.454(4)–2.511(4) Å and 2.572(6)–2.635(4) Å for the Sr–O and Sr–N linkages, respectively. All ketoiminate ligands are bonded in μ,η²-mode leading to an unprecedented structural motif, with the amine functionality remaining pendant, probably due to the steric hindrance of the diisopropylamino moiety.     

The tetramethylguanidine catalyzed Baylis–Hillman reaction: Effects of co-catalysts and alcohol solvents on reaction rate

We report here the effects on the rate of the tetramethylguanidine catalyzed Baylis–Hillman reaction of addition of co-catalysts or alcohol solvents. We find that the use of phenol as a co-catalyst leads to significant rate acceleration. The reaction is best performed at 48 °C, with the reaction reaching completion within 1 h. The catalyst mixture works for aromatic aldehydes but not aliphatic aldehydes. Using methanol and ethanol as solvents has also been investigated and a rate acceleration over the solvent free case is observed but not to the same extent as with phenol.