Synthesis and properties of aromatic polyesters and brominated polyesters derived from α,α′-bis(4-hydroxyphenyl)-1,4(or 1,3)-diisopropylbenzene

The interfacial polycondensation technique was used for the preparation of polyarylates and brominated polyarylates. Polyarylates and brominated polyarylates were prepared by mixing a solution of diacid chloride such as terephthaloyl chloride, isophthaloyl chloride, or their mixture in dichloromethane with an aqueous alkaline solution of ,-bis(4-hydroxyphenyl)-1,4(or 1,3)-diisopropylbenzene or ,-bis(4-hydroxy-3,5-dibromophenyl)-1,4(or 1,3)-diisopropylbenzene using triethylbenzylammonium chloride as the phase transfer agent. Moderate to high molecular weight polyarylates with _inh up to 1.27 dL/g were obtained, and most of them could be cast into tough and flexible films depending on the polymer composition. In general, polymers containing more 1,3-isomer or isophthaloyl chloride moieties gave transparent and flexible films and had lower glass transition temperatures and higher solubility. Although these polymers have two isopropylidene linkages in their repeating units, they still exhibit moderately high thermal stability and show no obvious weight loss before 400 °C. The introduction of bromine on the polymer backbone caused a decrease of inherent viscosity, crystallinity, and thermal stability of the polyarylates, while causing an increase in glass transition temperature and a great enhancement of fire retardancy.     

Oxidation of α- and β-pinene catalyzed by MnIII (Salen) Cl·H2O

The cationic complex Mn^III (Salen) is a very effective catalyst for the oxidation of both- and-pinene. The higher selectivity towards epoxide formation supports the rebound oxygen mechanism. A turnover of 40 was obtained for both compounds after 16 h of reaction with a molar ratio 10.011 (feedstock: catalyst: iodosobenzene) and conversions between 50 and 60% were observed. A very high selectivity (55%) was determined for epoxide formation from -pinene. The good selectivity observed for myrtanal isomers (6.5 and 23.2%) from-pinene is related to the prior formation of the 1,2-epoxides.     

Grinding-induced rapid,convenient and solvent free approach for the one pot synthesis of α-aminophosphonates using aluminium pillared interlayered clay catalyst

An easy to prepare aluminium pillared interlayered clay (PILC) has been developed as a stable, recyclable and heterogeneous catalyst to promote the one-pot three component synthesis of α-aminophosphonates under solvent-free conditions using grindstone chemistry. Utilization of mild reaction conditions, clean conversion and greater selectivity under grinding conditions along with effortless separation, and purification of reaction products make this process extra attractive.     

Nickel complex-mediated copolymerization of regioisomeric 5,5′-bis(chlorobenzoyl)-2,2′-dimethoxybiphenyls: synthesis of wholly aromatic copolyketones

Aromatic coupling copolymerization of 5,5^′-bis(4-chlorobenzoyl)-2,2^′-dimethoxybiphenyl (1) and 5,5^′-bis(3-chlorobenzoyl)-2,2^′-dimethoxybiphenyl (2) has successfully afforded higher-molecular-weight polyketones than either of the corresponding homopolymerizations. The wholly aromatic copolyketones thus obtained have highly amorphous nature with high glass transition temperatures (T_g).     

A facile one-pot ultrasound assisted synthesis of 1,8-dioxo-octahydroxanthene derivatives catalyzed by Brønsted acidic ionic liquid (BAIL) under green conditions

A simple and efficient one-pot procedure for the synthesis of 1,8-dioxo-octahydroxanthene derivatives in water under ultrasound irradiation is described. These heterocycles were prepared by condensation of dimedone with various aromatic aldehydes in the presence of Brønsted acidic ionic liquids as a convenient, cheap, readily synthesized and eco-friendly catalyst. This procedure has a lot of advantages such as: excellent yields, simplicity of the workup, low cost, short reaction times and green conditions. Ionic liquids could be recycled several times without significant loss of activity and high purity.     

Simple but efficient synthesis of bis(indolyl)methanes by the condensation reaction of substituted benzaldehydes with indole over mesoporous ZrO<Subscript>2</Subscript>–MgO green catalysts under solvent free conditions

Solid base catalytic materials such as ZrO₂, MgO, ZrO₂–MgO were prepared by either precipitation or impregnation method and characterized by, BET, CO₂-TPD, PXRD, FT-IR, ICP-OES and TEM techniques. These catalysts were used for the synthesis of bis(indolyl)methanes by the condensation of different benzaldehydes with indole under solvent free conditions in shorter reaction times (20 min) at moderate temperature (70?°C). ZrO₂/MgO catalyst was found to be highly basic and also resulted in high yields of bis(indolyl)methanes up to ~99%. This methodology offers several advantages such as high quality yields, easy procedure, mild and environmentally benign conditions. TEM studies revealed that ZrO₂–MgO is mesoporous (25–45 nm) in nature. ZrO₂–MgO catalysts were found to be economical, efficient and were found to be highly active, recyclable and reusable up to six reaction cycles without much loss of their activity.     

Oxidation of catechol catalyzed by β-cyclodextrin-Cu(Ⅱ) complexes and its reaction kinetics

以β-环糊精(β-CD)作为骨架,经磺酰化反应、卤代反应和与L-组氨酸的亲核取代反应,得到了两种β-环糊精-组氨酸衍生物配体,再将配体与Cu(Ⅱ)配位,合成了具有多酚氧化酶催化活性的β-环糊精-Cu(Ⅱ)配合物。采用元素分析、傅里叶变换红外光谱、核磁共振波谱和原子吸收光谱等方法对配体和配合物的结构进行了表征。以O₂为氧化剂,用分光光度法测定了它们催化邻苯二酚氧化反应的性能,并考察了反应温度、pH值等因素对催化反应速率的影响。结果表明：β-环糊精-Cu(Ⅱ)配合物具有良好的催化性能;C-2位修饰得到的环糊精类金属衍生物因为活性基团与反应中心之间相对位置适宜,表现出较大的加速效果;反应动力学表明组胺基配位Cu(Ⅱ) 、β- CD疏水空腔和碱催化作用是反应加速的3个因素。     

A novel and efficient procedure for the preparation of 4,4′-bis(chloromethyl)biphenyl by chloromethylation of biphenyl catalyzed by PEG1000-DAIL under homogeneous catalysis in aqueous media

As described in this article, 4,4′-bis(chloromethyl)biphenyl was obtained in 85% excellent yield by chloromethylation of biphenyl catalyzed by the recyclable temperature-dependant phase-separation system that comprised the dicationic acidic ionic liquid PEG₁₀₀₀-DAIL and methylcyclohexane under homogeneous catalysis in aqueous media. Compared to other synthetic methods, the novel method not only enhanced the yield, but also made the operating units easy workup. The mechanism of chloromethylation reaction and the process of catalysis in the thermoregulated ionic liquid bi-phase system were proposed.     

Synthesis of well-defined bisbenzoin end-functionalized poly(ε-caprolactone) macrophotoinitiator by combination of ROP and click chemistry and its use in the synthesis of star copolymers by photoinduced free radical promoted cationic polymerization

A new well-defined bisbenzoin group end-functionalized poly(ε-caprolactone) macrophotoinitiator (PCL-(PI)₂) was synthesized by combination of ring opening polymerization (ROP) and click chemistry. The ROP of ε-CL monomer in bulk at 110 °C, by means of a hydroxyl functional initiator namely, 3-cyclohexene-1-methanol in conjunction with stannous-2-ethylhexanoate, (Sn(Oct)₂), yielded a well-defined PCL with a cyclohexene end-chain group (PCL-CH). The bromination and subsequent azidation of the cyclohexene end-chain group gave bisazido functionalized poly(ε-caprolactone) (PCL-(N₃)₂). Separately, an acetylene functionalized benzoin photoinitiator (PI-alkyne) was synthesized by using benzoin and propargyl bromide. Then the click reaction between PCL-(N₃)₂ and PI-alkyne was performed by Cu(I) catalysis. The spectroscopic studies revealed that poly(ε-caprolactone) with bisbenzoin photoactive functional group at the chain end (PCL-(PI)₂) with controlled chain length and low-polydispersity was obtained. This PCL-(PI)₂ macrophotoinitiator was used as a precursor in photoinduced free radical promoted cationic polymerization to synthesize an AB₂-type miktoarm star copolymer consisting of poly(ε-caprolactone) (PCL, as A block) and poly(cyclohexene oxide) (PCHO, as B block), namely PCL(PCHO)₂.     

Hydrolysis of mechanically pre-treated cellulose catalyzed by solid acid SO_4~(2-)-TiO_2 in water–ethanol solvent

An efficient catalyst SO_4~(2-)-TiO_2(ST) from industrial metatitanic acid has been successfully prepared to catalyze hydrolysis of ball-milling cellulose. The results show that the highest catalytic efficiency is obtained for ST calcined at 450 °C(ST-450) with the yield of 21.8% glucose, 13.0% 5-HMF and 4.2% furfural at 200 °C for30 min. The ball milling of cellulose and solid acid catalyst significantly enhances the cellulose hydrolysis. The high Lewis to Br?nsted acid sites ratio for ST-450 induced by bidentate ligands between SO_4~(2-)and TiO_2 benefits high organics yield, and high total acid sites contribute to the high cellulose conversion. The large pore volume of0.29 cm~3·g~(-1) and appropriate pore size of 7.35 nm of ST-450 also contribute to the high performance. High reaction temperature over 200 °C exhibits negative effect on glucose and 5-HMF yield due to undesired side reactions, while furfural product is stable in the reaction system. The bidentate ligands between SO_4~(2-)and TiO_2 are considered as active acid sites for cellulose hydrolysis in water–ethanol solvents.     

The efficient synthesis of poly(silapropynylenes) via condensation of NaCэCNa with R1R2SiCL2 activated by pyridine

Summary To efficiently prepare poly(silapropynylenes), the condensation of NaCCNa with R₁R₂SiCl₂ activated by pyridine were investigated. The condensation produced tactable polymers(Mw ca. 2100–9000) with significantly higher yields of 80–97% than those from R₁R₂SiCl₂ itself and also gave rise to much more improvement in the yields and molecular weight than with acetylenic di Grignard or di lithium salts. The activation of R₁R₂SiCl₂ by pyridine accelerated the condensation reaction, which resulted in production of macrocyclic polymers as well as linear polymers.     

Hydrothermal synthesis and tuning of size and morphology of α-Co(OH)2 and α-Co2(OH)3Cl nanostructures as precursors for nanosized Co3O4

This study aims to investigate the hydrothermally synthesized cobalt(II) hydroxide-based materials, which will be thermally converted to generate Co₃O₄ nanostructures; an important class of materials characterized by good electrochemical, catalytic and optical properties. First, cobalt(II) hydroxide nanostructures were prepared via hydrothermal hydrolysis of two different precursors (cobalt(II) chloride salt and dichlorobis(thiourea)cobalt(II) complex) exposure to an ammonia atmosphere, and then the obtained α-Co(OH)₂ and α-Co₂(OH)₃Cl nanostructures were calcined to produce Co₃O₄ nanostructures that were characterized by FT-IR, XRD, UV–vis DRS and SEM techniques. The effects of the nature of the precursor, its concentration, and of the temperature and reaction time on size and morphology of the product were also investigated.     

The synthesis and characterization of a mesomorphic brush type polycarbosilane: poly[1,1-bis(4′-biphenyl)silabutane]

Summary Poly[1,1-bis(4-biphenyl)silabutane] (II) has been prepared by the anionic ring opening polymerization of 1,1-bis(4-biphenyl)silacyclobutane. II shows mesomorphic behavior by DSC. The¹³C NMR T₁ relaxation times have been measured. These are found to be smaller than those of poly(1,1-dimethylsilabutane)by an order of magnitude. This may result from interaction of the highly rigid biphenyl side chain moieties. The thermal stability of II is higher than that for other 1,1-disubstituted polysilabutanes.     

PEG-directed microwave-assisted hydrothermal synthesis of spherical α-Ni(OH)2 and NiO architectures

Spherical α-Ni(OH)₂ architectures were synthesized by the microwave-assisted hydrothermal technique using PEG-6000 as the surfactant. NiO architectures with similar morphology were obtained by a simple thermal decomposition process of the precursor α-Ni(OH)₂ at 400 °C for 2 h and were confirmed by the X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) revealed that the synthesized spherical α-Ni(OH)₂ and NiO architectures were composed of stacked lamellar sheets and transmission electron microscopy (TEM) showed that the α-Ni(OH)₂ and NiO architectures were polycrystalline. The effect of the PEG-6000 concentration on particle size was investigated and it was found that the average particle size of α-Ni(OH)₂ architectures decreased from 4.689 μm at C_PEG=2 mmol L⁻¹ to 3.907 μm at C_PEG=4 mmol L⁻¹, and the corresponding average particle size of NiO decreased from 2.818 μm to 2.492 μm. The optical absorption band gap of NiO architectures was determined to be about 2.7–3.0 eV by UV–vis spectroscopy.     

Synthesis of mesoporous α-MnO2 in manganese(II)-based deep eutectic solvent and their application in the absorption of Congo red

Mesoporous alpha-manganese dioxide (α-MnO₂) were synthesized from manganese(II)-based deep eutectic solvent (DES) of MnCl₂?4H₂O and acetamide in a 1:7 molar ratio. The DES can act as solvent and reducing reagent. As-prepared samples were characterized and used as absorbents for the removal of Congo red (CR) from aqueous solutions. Results show that the sample prepared at 70°C (M-70) could remove 93% CR from aqueous solutions in 30 min. The maximum adsorption capacity of the M-70 was estimated to be 54.85 mg/g. Finally, the exhausted M-70 can be regenerated by thermal desorption.     

Regeneration of [Fe(II)-NTA]− catalyzed by activated carbon in the simultaneous removal of sulphur dioxide and nitric oxide

The combined control of NO and SO₂ can be finished with the [Fe(II)-NTA]⁻ solution because [Fe(II)-NTA]⁻ is capable of binding NO. However, the ability of [Fe(II)-NTA]⁻ to bind NO may be lost quickly due to the fast oxidation of [Fe(II)-NTA]⁻ to [Fe(III)-NTA] by oxygen in the flue gases. To make it possible to put this technology into commercial application, efficient measures should be taken to regenerate [Fe(II)-NTA]⁻ to maintain the NO removal efficiency for a long time. The catalytic activity of activated carbon in the reproduction of [Fe(II)-NTA]⁻ has been investigated in a fixed-bed reactor. The experiments indicate that [Fe(II)-NTA]⁻ reproduction increases with [Fe(III)-NTA] and SO₃²⁻ concentrations as well as temperature. Fast flow and high pH are unfavourable for the reproduction of [Fe(II)-NTA]⁻. An NO removal efficiency of 80.11%–89.78% is sustained for a long period of time with the [Fe(II)-NTA]⁻ reproduction catalyzed by activated carbon. The reaction orders with respect to [Fe(III)-NTA] and SO₃²⁻ are 0.784 and 0.336, respectively. The apparent activation energy for this catalytic reaction is estimated to be 41.01 kJ mol⁻¹.     

Efficient oxidative desulfurization (ODS) of model fuel with H2O2 catalyzed by MoO3/γ-Al2O3 under mild and solvent free conditions

An efficient process to remove organic sulfur compounds from model fuel has been explored. Dibenzothiophene (DBT) and 4, 6-dimethyldibenzothiophene (4, 6-DMDBT) can be completely oxidized into their corresponding sulfones by H₂O₂ over 14 wt.% MoO₃/γ-Al₂O₃ catalyst under mild conditions in 15 min. The effects of solvent, initial sulfide concentration, loading of MoO₃ and amount of catalyst on oxidative removal of DBT were studied. The employments of solvents have decreased the reaction rate of DBT, which can be attributed to the competitive adsorption between the sulfide and solvent. The oxidative reactivity increases in the order of thiophene (Th) < benzothiophene (BT) < DBT < 4, 6-DMDBT. The catalyst can be regenerated by methanol washing at 333 K.