Cryochemical Synthesis of Mn-Containing Poly(p-Xylylene)

A Mn-containing polymer was produced by solid-state photopolymerization of a cocondensated mixture of p-xylylene with Mn at 80 K. It was shown that during simultaneous deposition p-xylylene and Mn formed both - and -complexes. Irradiation of the system by UV light resulted in polymerization of p-xylylene with the destruction of the unstable -complexes, while the -bonded compounds were incorporated into the polymer chains. Complexes of Mn with benzyl-type radicals of the polymerized system were also observed. Prolonged storage of the polymerized material at ambient temperature under vacuum led to the gradual decomposition of the organomanganese compounds and complexes.     

Catalytic activity of nickel nanoparticles in hydrogenation of p-nitrophenol to p-aminophenol

Nickel nanoparticles with different sizes and different structures were prepared by reducing nickel oxalate with hydrazine hydrate in the presence of citric acid, sodium dodecyl sulphonate, Tween 80, PEG 6000, and D-sorbitol as organic modifiers. The type of organic modifiers affected the size and the structure of the resultant nickel nanoparticles. The catalytic activities of the nickel nanoparticles increased with decreasing the particle size in the hydrogenation of p-nitrophenol to p-aminophenol. All the as-prepared nickel nanoparticles showed higher catalytic activity and selectivity than conventional Raney Ni catalyst.     

Morphological investigations of self-assembled films from a pyridine -incorporated poly (p-phenylene)

Well-organized structures of polymers in thin films have been widely investigated. Amphiphilic polymers, star-shaped polymers and modified polystyrene-based polymers have been shown to form self-assembled honeycomb patterns on substrates. Herein, we report a poly (p-phenylene) derivative capable of producing self-assembled regular structures. Highly fluorescent honeycomb structures were observed on various substrates. The nature of the substrate and polymer influences the morphology of the film.     

Statistical optimization of process variables in batch alkylation of p-cresol with tert-butyl alcohol using ionic liquid catalyst by response surface methodology

Alkylation of p-cresol with tert-butyl alcohol was studied using ionic liquid catalyst prepared from N-(1,4-sulfonic acid) butyl triethylammonium hydrogen sulfate. An experimental design using response surface methodology (RSM) is used to optimize the process parameters in this batch alkylation to minimize rigorous experimental procedures and conserve the catalyst. The parameters, namely, temperature, reactant mole ratio, catalyst (IL) to p-cresol mole ratio and time of reaction on the conversion of p-cresol and yield of 2-tert-butyl-p-cresol (TBC) were optimized using Box–Behnken design. Low temperature, low p-cresol to alcohol ratio and low catalyst (IL) to p-cresol ratio in a batch reactor were found to maximize conversion of p-cresol and yield of TBC.     

Process research of macroporous resin chromotography for separation of N-(p-coumaroyl)serotonin and N-feruloylserotonin from Chinese safflower seed extracts

N-(p-Coumaroyl)serotonin (CS) and N-feruloylserotonin (FS) are two bioactive serotonin derivatives in safflower (Carthamus tinctorius L.) seeds with many biological effects. In the present study, the sorption and desorption characteristics of six widely used macroporous resins, coded D312, 860021, DM131, HZ801, AB-8 and XDA-1, respectively, is critically evaluated and compared for enrichment and preparative separation of CS and FS. Static adsorption and desorption experiments on these resins showed that XDA-1 had the best adsorption and desorption equilibrium for CS and FS, and its adsorption equilibrium fits the best to the Langmuir isotherm. Dynamic adsorption and desorption experiments on XDA-1 resin packed column were conducted to establish the optimum parameters as: CS and FS concentration in sample solution 0.346 and 0.276 mg/mL, respectively, sample size 5-bed volumes (BV), sample flow rate 2 mL/min, temperature 25 °C (for adsorption); eluent 80% ethanol, 11 BV, flow rate 1 mL/min (for desorption). After one run of adsorption and desorption, the contents of CS and FS were increased from 2.01%, 1.67% to 24.1% and 22.4%, and the recoveries were 77.2% and 68.5%, respectively. The chromatographic process optimized in the present work is a promising basis for large scale preparation of CS and FS upon further scaling up tests.     

Synthesis and characterization of a renewable cyanate ester/polycarbonate network derived from eugenol

A homogenous polycarbonate/cyanate ester network has been prepared from a renewable, eugenol-derived bisphenol. The pure polycarbonate exhibited a T_g of 71 °C, M_n = 8360, and polydispersity of 1.88. An 80:20 blend of cyanate ester: polycarbonate was prepared and thermally cured. The presence of the polycarbonate had no significant effect on the cure behavior of the cyanate ester. Small Angle Laser Light Scattering (SALLS) and DSC were used to analyze the blend and no phase separation was observed either during or after cure, suggesting that a homogenous network was generated. TMA of the resulting composite material revealed a single T_g of 132 °C (tan δ), roughly 55 °C lower than the T_g of the pure polycyanurate and 60 °C higher than the polycarbonate. A solvent extraction study showed that the polycarbonate could be quantitatively separated from the thermoset matrix after cure. This result proved that no chemical grafting occured under the cure conditions employed. The excellent miscibility of the polycarbonate and cyanate ester coupled with the efficient cure of the blend to a homogenous network suggests that these types of blends may have applications for fabrication of toughened composite structures.     

Semi-empirical calculation and spectroscopic study of protonated poly(p-phenylene benzobisoxazole) models

The characters of poly(p-phenylene benzobisoxazole) (PBO) in methanesulfonic acid (MSA) are strongly influenced by the protonation effect. Due to such protonation effect, the experimental optical absorption spectrum was red shifted from the optical absorption spectrum predicted by AM1/ZINDO–CI (Austin Method 1/Zerner's intermediate neglect of differential overlap coupled to single configuration interaction) method. Further studies on AM1-optimized geometries of PBO showed that the final minimized torsion angle of benzoxazole and phenylene rings increased from 0.04° for the neutral molecule to 18.53° for protonated form at N atom. Moreover, the repulsive Coulombic interactions originated from protonation tend to stiffen the PBO chain. The AM1/ZINDO–CI calculation also indicated that the strongest UV absorption peak of PBO was blue shifted with increasing torsion angle.     

12-Tungstophosphoric acid immobilized on modified macroporous phenol-furfural sulfonic acid resin for tert-butylation of p-cresol.

12-Tungstophosphoric acid (HPW) had been immobilized on phenol-furfural sulfonic acid resin (PFuSR) using γ-aminopropyltriethoxy silane (KH). FT-IR spectra indicate that the immobilized HPW on KH modified PFuSR (PFuSR-KH) keeps its Keggin structure and IR subtraction spectra confirm the immobilization of HPW on PFuSRKH through the interaction between amino groups of KH and bridge oxygen atom of W₃O₁₃. XRD patterns of the HPW illustrate that its second-order structure is changed greatly after being immobilized. The immobilized HPW on KH-modified PFuSR not only maintains its selectivity but also possesses high acidic activity in catalyzing t-butylation of p-cresol with t-butanol, though the by-product water hindered the reaction. The PFuSR-KH-immobilized HPW loses only half of its activity after being reused five times, while the PFuSR-supported one has no catalytic activity in the second run.     

The improvement of boron-doped diamond anode system in electrochemical degradation of p-nitrophenol by zero-valent iron

Boron-doped diamond (BDD) electrodes are promising anode materials in electrochemical treatment of wastewaters containing bio-refractory organic compounds due to their strong oxidation capability and remarkable corrosion stability. In order to further improve the performance of BDD anode system, electrochemical degradation of p-nitrophenol were initially investigated at the BDD anode in the presence of zero-valent iron (ZVI). The results showed that under acidic condition, the performance of BDD anode system containing zero-valent iron (BDD-ZVI system) could be improved with the joint actions of electrochemical oxidation at the BDD anode (39.1%), Fenton's reaction (28.5%), oxidation–reduction at zero-valent iron (17.8%) and coagulation of iron hydroxides (14.6%). Moreover, it was found that under alkaline condition the performance of BDD-ZVI system was significantly enhanced, mainly due to the accelerated release of Fe(II) ions from ZVI and the enhanced oxidation of Fe(II) ions. The dissolved oxygen concentration was significantly reduced by reduction at the cathode, and consequently zero-valent iron corroded to Fe(II) ions in anaerobic highly alkaline environments. Furthermore, the oxidation of released Fe(II) ions to Fe(III) ions and high-valent iron species (e.g., FeO²⁺, FeO₄²⁻) was enhanced by direct electrochemical oxidation at BDD anode.     

Synthesis, characterization and catalytic properties of an N-heterocyclic carbene palladium-based complex

A palladium(II) complex, bis[1,3-bis-(2,4,6-trimethylbenzyl)benzimidazol-2-ylidene]palladium(II) chloride, Pd(NHC), bearing N-heterocyclic carbenes has been synthesized and characterized by elemental analysis, IR spectroscopy and ¹H and ¹³C NMR spectroscopy. Crystal structure details of Pd(NHC) are also presented. The palladium centre in the complex lies on a crystallographic inversion centre and occupies a square-planar environment, with both chloride and N-heterocyclic carbene ligands adopting a trans arrangement with Cl–Pd–Cl and C–Pd–C angles are precisely 180°. The palladium–carbene complex was tested as a catalyst in the Suzuki–Miyaura cross-coupling reaction.     

Microwave-assisted epoxidation of styrene with molecular O2 over sulfated Co–Y–ZrO2 solid catalyst

The microwave-assisted styrene epoxidation reaction with molecular O₂ as an oxidant was studied over a sulfated Co–Y-doped ZrO₂ solid catalyst. The microwave irradiation (400 W) resulted in similar styrene conversion and styrene oxide selectivity, in reduced time, as compared to conventional thermal heating. Higher power (800 W) of microwave irradiation decreased the styrene oxide selectivity as well as leading to the formation of styrene glycol. DMF was found to be the most suitable solvent for epoxidation of styrene with molecular O₂ under microwave irradiation and yielded maximum oxide selectivity (91%) at 120 °C. The microwave-assisted oxidation reaction resulted in time saving and is energy conserving method.     

Sensory Thresholds of Selected Phenolic Constituents from Thyme and their Antioxidant Potential in Sunflower Oil

The odor detection thresholds of carvacrol (5-isopropyl-2-methyl-phenol), thymol (2-isopropyl-5-methyl-phenol) and p-cymene 2,3-diol (2,3-dihydroxy-4-isopropyl-1-methyl-benzene) in sunflower oil, determined by the three-alternative, forced-choice procedure, were 30.97, 124 and 794.33 mg kg⁻¹, respectively. Sunflower oil containing 13, 70, or 335 mg kg⁻¹ of carvacrol, thymol or p-cymene 2,3-diol, respectively, was judged to be similar (P < 0.01) in taste and odor to its antioxidant-free counterpart. The rate constant of sunflower oil oxidation, measured from the increase in peroxide value during storage at 25 °C, was 9.2 × 10⁻⁹ mol kg⁻¹ s⁻¹ while the rate constants were 9.3 × 10⁻⁹, 9.8 × 10⁻⁹, and 4.3 × 10⁻⁹ mol kg⁻¹ s⁻¹ in the presence of 13 mg kg⁻¹ carvacrol, 70 mg kg⁻¹ thymol, and 335 mg kg⁻¹ p-cymene 2,3-diol, respectively. At a level of 335 mg kg⁻¹, p-cymene 2,3-diol did not impart flavor taints and effected a 46.7% reduction in the rate of oxidation of sunflower oil. These findings indicate that the diphenolic p-cymene 2,3-diol could potentially replace synthetic antioxidants and is a valuable addition to the antioxidants used by the food industry in its quest to meet consumer demands for synthetic-additives-free and ‘natural’ foods.     

Synthesis of a fatty tetrahydroxyamide using peroxygenase from oat seeds

Prior work has shown that oat (Avena sativa) seeds are a rich source of lipase and peroxygenase. Partial epoxidation of the isobutyl amide derivative of α-linolenic acid with peroxygenase gave N-i-butyl-9, 10–15, 16-diepoxy-12(Z)-octadecenamide, a diepoxide product in which the epoxides reside only at the formerly external double bond positions. No amide hydrolysis occurred during the epoxidation procedure. Hydrolysis of the diepoxide gave N-i-butyl-9, 10,15,16-tetrahydroxy-12 (Z)-octadecenamide, a polyol derivative with relatively high polarity, potentially useful in developing new materials from fats and oils.     

Study on Copper-based Catalysts for Synthesis of N,N′-bis(1,4-dimethylpentyl)-p-phenylenediamine from Reductive Alkylation of p-Nitroaniline with 5-Methyl-2-hexanone

The reductive alkylation of p-nitroaniline with 5-methyl-2-hexanone over copper-based catalysts was investigated. Furthermore, the catalysts were characterized using the techniques of XRD, H₂–N₂O titration, H₂-TPR, NH₃-TPD and pyridine-FTIR. The results showed that the addition of Mn, Ba and La into Cu–SiO₂ catalyst played an important role in the improvement of the selectivity towards N,N′-bis(1,4-dimethylpentyl)-p-phenylenediamine (BMPPD). The highest selectivity towards BMPPD over 58CuO–9MnO₂–BaO–1La₂O₃–30SiO₂ (wt.%) catalyst could be ascribed to the best dispersion of copper (i.e., the highest hydrogenation ability) and the most amounts of the surface Lewis acidic sites.     

Synthesis of Ethyl 5 Z ,9 Z ,12 Z -octadecatrienoate (ethyl pinolenate) and Methyl 12 Z ,15 Z -octadecadienoate

Pinolenic acid (5Z,9Z,12Z-octadecatrienoic acid, 1a), one of the most abundant trienoic fatty acids in nature, is very difficult to obtain in quantity in a pure state from the highly complex mixture of unsaturated tall oil fatty acids. For this reason its chemistry has been little studied when compared to linolenic or linoleic acids. A simple synthesis of esters of 1a and of 12Z,15Z-octadecadienoic acid 3 using the one pot double Wittig procedure is described here. The products of double Wittig reactions were purified by argentation chromatography, and their structural purity was established by ¹H-, ¹³C-NMR and 2D-NMR spectroscopies.

Identification, Synthesis, and Field Evaluation of the Sex Pheromone from the Citrus Leafminer, Phyllocnistis citrella

Using male antenna as the sensing element, three electroantennographic detection (EAD)-active peaks were detected from pheromone gland extracts of the citrus leafminer, Phyllocnistis citrella. Based on gas chromatography (GC)-mass spectrometry and GC-infrared data, the semiochemicals were tentatively identified as a novel pheromone, (Z,Z,E)-7,11,13-hexadecatrienal, a previously identified attractant, (Z,Z)-7,11-hexadecadienal, and (Z)-7-hexadecenal in a ratio of 30:10:1, respectively. Identification was confirmed with synthetic compounds, which gave retention times identical to those of the natural products on three capillary columns with polar and nonpolar phases. While traps baited only with the previously identified attractant alone did not catch any males in Brazil, binary and tertiary mixtures with the major constituents caught significantly more male moths than traps baited with five virgin females. This paper and the following paper (Moreira et al.) were submitted within a few days of each other. The editors and the authors agreed that they should be published in tandem.     

Synthesis of pure zeolite Y using soluble silicate, a two-level factorial experimental design

Four methods were used for the synthesis of pure zeolite Y using soluble silicate as a silica source: (1) the gelling of soluble silicate to silica–alumina gel, by aluminate (or aluminium sulphate), (2) the precipitation of soluble silicate to precipitated silica–alumina gel, by aluminate (or aluminium sulphate), (3) the gelling of soluble silicate by sulphuric acid plus alumina impregnation, and (4) the precipitation of soluble silicate by sulphuric acid plus alumina impregnation. A 2⁴ two-level factorial design was used to study the influence of four different variables on the purity of zeolite Y (expressed in terms of degree of crystallinity). The ageing time turned out to be the most significant variable. Synthesis time, alkalinity and mixing rate were also found to be statistically significant. X-ray diffraction patterns were used to characterize the samples, which ranged from well-crystallized faujasite structures to amorphous materials. The highest purity achieved in method (1) was 38%. The best synthesis condition derived from method (1) was applied to the other three methods. Only method (4) yielded the pure zeolite Y. Therefore, the effect of silica–alumina precursor preparation on producing the pure zeolite Y is extremely important.