Assembly of Terpenoid Cores by a Simple,Tunable Strategy

Oxygenated, polycyclic terpenoid natural products have important biological activities. Although total synthesis of such terpenes is widely studied, synthetic strategies that allow for controlled placement of oxygen atoms and other functionality remains a challenge. Herein, we present a simple, scalable, and tunable synthetic strategy to assemble terpenoid‐like polycycloalkanes from cycloalkanones, malononitrile, and allylic electrophiles, abundantly available reagent classes.     

Itaconamide derivatives as organic stabilizers for poly(vinyl chloride) against photodegradation

Itaconamide derivatives have been prepared and investigated as photo-stabilizers for rigid PVC. We investigated their stabilizing efficiencies by testing the weight loss (%) with the amount of formed gel. The results indicated a reasonable stabilizing efficiency of these derivatives compared with commercial UV absorber; phenyl salicylate. The extent of discoloration of the photodegraded polymer was also improved in the presence of the prepared compounds. Rheological properties were studied to investigate the flow behavior with providing a vision into the mechanical behavior for the tested materials. Employing the evaluated photostabilizers reflects the reduction in the extent of cross-linking of the polymer. This implies preserving the mechanical properties of PVC. A radical mechanism is proposed to account for the stabilizing action of the investigated materials. The prepared itaconamide derivatives provide appropriate photostability and mechanical properties for a durable poly(vinyl chloride).     

Vinylazides: versatile synthons and magical precursors for the construction of N-heterocycles

Molecular Diversity - Nowadays, application of vinylazides as precursors is a key method for the construction of N-heterocycles in organic synthesis. These versatile three-atom synthons can be...     

Model Discrimination in Copolymerization Using the Sequential Bayesian Monte Carlo Method

The authors have introduced and extended the sequential Bayesian Monte Carlo model discrimination (SBMCMD) method described in previous studies by Masoumi et al. for the purpose of discriminating between mechanistic models via designed experiments. The features of the Markov Chain Monte Carlo methods utilized in SBMCMD allow this method to work with a wide range of nonlinear models. Here, SBMCMD has been applied to simulated copolymerization systems to compare its performance with other statistical discrimination methods used in previous studies by Burke et al. In addition, the Hsiang and Reilly method has been reapplied to the same copolymerization systems to address questions arising from previous work on this subject. The results of applying the SBMCMD method show that it is possible to choose the best model correctly with fewer experiments compared to the previously studied methods. Results also confirm that copolymer composition data do not provide enough information to discriminate between terminal and penultimate data.

     

Effect of post‐deposition annealing on surface morphology and gas sensing properties of palladium phthalocyanine thin films

The effect of post‐deposition annealing on surface morphology and gas sensing properties of palladium phthalocyanine (PdPc) nanostructured thin films has been studied. PdPc thin films were deposited on polyborosilicate substrate by thermal evaporation technique at room temperature. The surface morphology of thin films was investigated by SEM, X‐ray diffraction, and optical absorption. X‐ray diffraction patterns showed a phase transition from α to β based on post‐deposition annealing at temperatures above 200 °C. The SEM and optical absorption confirmed that annealing strongly influenced the surface morphology of nanostructured thin films. Sandwich devices (Au|PdPc|Al) were fabricated and exposed to different concentrations of NO₂ and NH₃ as oxidizing and reducing gases at different temperatures, and the sensitivity of devices were obtained versus gases. Obtained results showed α‐PdPc thin film devices had higher sensitivity in comparison with devices in β‐phase. In particular, it was found that the sensitivity of devices is temperature dependent and the best operating temperature range of devices was measured at about 90–100 °C. Devices showed good reversibility, response, and recovery time at room temperature. Finally, the stability of sensors was investigated for a period of about 1 year; results showed that the sensors were stable for 2 months and lost about 30% of their sensitivity after 1 year. Copyright © 2012 John Wiley & Sons, Ltd.     

Origin of semiconductor and half-metallic behaviors in the perovskite materials RbXF3 (X = Co,Mn, Fe or V): A GGA + U approach

In this paper, we study and discuss the structural, and electronic properties of the RbXF3 (X = Co, Mn, V or Fe) Perovskite Materials using the Density Functional Theory (DFT). Also, the origin of both semi-conductor (SM) and half-metallic (HM) characters have been outlined. The density functional theory (DFT) has been applied to illustrate the physical properties of the RbXF₃ (X = Co, Mn, Fe or V) perovskite materials. The generalized gradient approximation introduced by Perdew–Burke and Ernzerhof (GGA-PBE) with Hubbard correction has been used for modeling the physical properties of the RbXF₃ (X = Co, Mn, V or Fe) perovskite compounds. The total and partial densities of states of each solar perovskite RbVF₃ (X = Co, Mn, Fe or V) material have been illustrated and discussed. In addition, the contribution of the different elements: Rb, Co, Mn, Fe, V and F, has been investigated revealing the most contributing ones in the valance and conduction bands. The magnetic behavior of the studied solar perovskites RbVF₃ (X = Co, Mn, Fe or V) materials, has been outlined. It is found that the perovskites RbCoF₃ and RbFeF₃ are half-metallic, while the materials RbMnF₃ and RbVF₃ exhibit a semi-conductor behavior.     

Ultrafast laser machining of tapered microchannels in glass and PDMS

The ability to fabricate tapered microchannels with customizable cross sections in a variety of materials is highly desirable for microfluidic applications. This article examines ultrafast laser machining of tapered microchannel trenches in both hard (soda-lime and borosilicate glasses) and soft (PDMS elastomer) transparent solids. A simple model for channel width and depth as a function of processing parameters and threshold fluence is presented. Estimated channel sizes from the model are in good agreement with experimental results. We also show that the channel depth is a linear function of the number of laser pulses per channel width. All measurement data are found to collapse onto a single curve, which can serve as a useful guide for micromachining of tapered channels in transparent materials.     

A novel tridentate Schiff base dioxo-molybdenum(VI) complex: Synthesis,crystal structure and catalytic performance in green oxidation of sulfides by urea hydrogen peroxide

A new dioxo-molybdenum(VI) complex [MoO₂(L)(CH₃OH)] has been synthesized, using 2-[(2-hydroxypropylimino)methyl]phenol as tridentate ONO donor Schiff base ligand (H₂L) and MoO₂(acac)₂. A monoclinic space group P2₁/c was determined by X-ray crystallography from single-crystal data of this complex. The high catalytic activity of this new Schiff base complex has been observed in the oxidation of various sulfides by urea hydrogen peroxide in ethanol affording sulfoxides and sulfones using different molar ratio of oxidant/sulfide in high/excellent yields and selectivity under mild and eco-friendly conditions. The relative high stability and desired turnover numbers have been observed for this Mo-catalyst in the oxidation reactions.     

Extraction of male steroids and progesterone from water by vegetable oil gels and their determination by partial filling capillary micellar electrokinetic chromatography

Microemulsion gels were synthetized from macadamia, linseed, olive, walnut, rapeseed, sesame, and coconut oils and frying oil made from sunflower, palm, and rapeseed oils. The gels were similar as polyacrylamide–based gels with exception of replacing dodecyl sulfate with vegetable oils. The gels were modified with celluloses, cotton, or lignin to make the emulsions sustainable for water purification. They were used to compare sorption properties when they were used as solid‐phase adsorbents in isolation of steroids from water. Hydrophobicity features of the gels were compared by detecting adsorption and extraction efficiency of nonpolar androstenedione, testosterone, and progesterone, which exist in wastewater and drinking water. Quantification was done with partial filling–micellar electrokinetic chromatography with 29.5 mM sodium dodecyl sulfate–3.4 mM sodium taurocholate as the micelle and 20 mM ammonium acetate (pH 9.68) as the electrolyte. UV‐detection was used. Methanol was the best eluent for extraction of steroids from gels. The highest recoveries were from frying oil and rapeseed oil gels modified with celluloses. They also possessed the best floating properties on water surface. Lignin modified gels were too hydrophilic, when in touch with water they filled up with water. They also had the lowest capacity.