Copper-catalyzed hydrostannation of activated alkynes

[reactions: see text] [(Ph3P)CuH]6 effectively catalyzes the hydrostannation of activated alkynes with exclusive regioselectivity for alpha-stannation. Syn hydrostannation is observed exclusively for alkynoates. Anti or syn hydrostannation adducts are obtained as products for alkynone substrates.     

Compact beam expander based on planar structure to avoid inner focus

Optical Review - Based on the planar optical theory, compact beam expanders are proposed to miniaturize the dimension of an optical system. Both simulated and experimental results have demonstrated...     

Acid-Catalyzed Cyclodehydration of Quinazolone Prepolymers

The effect of p-toluenesulfonic acid and phosphoric acid on the cyclodehydration of quinazolone prepolymers has been investigated. Isothermal weight loss during the curing process was monitored closely to follow the extent of cyclization. The optimum weight loss corresponding to 2 mol water is used as an indication of the formation of a fully cyclized quinazolone structure without concurrent decarboxylation. This can be achieved by incorporating the catalyst at 2 wt% concentration, which permits a lower curing temperature than those previously reported. The polymers formed in the presence of catalyst have thermal stability superior to those prepared without catalyst. The glass transition temperature is also raised. This we conclude to be a direct result of the decrease in the amount of incomplete quinazolone rings along the polymer backbone as a result of more efficient cyclization catalyzed by the acids.     

Comparison of RAFT‐derived poly(vinylpyrrolidone) verses poly(oligoethyleneglycol methacrylate) for the stabilization of glycosylated gold nanoparticles

Carbohydrates dictate many biological processes including infection by pathogens. Glycosylated polymers and nanomaterials which have increased affinity due to the cluster glycoside effect, are therefore useful tools to probe function, but also as prophylactic therapies or diagnostic tools. Here, the effect of polymer structure on the coating of gold nanoparticles is studied in the context of grafting density, buffer stability, and in a lectin binding assay. RAFT polymerization is used to generate poly(oligoethyleneglycol methacrylates) and poly(N‐vinylpyrrolidones) with a thiol end‐group for subsequent immobilization onto the gold. It is observed that poly(oligoethylene glycol methacrylates), despite being widely used particle coatings, lead to low grafting densities which in turn resulted in lower stability in biological buffers. A depression of the cloud point upon nanoparticle immobilization is also seen, which might compromise performance. In comparison poly(vinylpyrrolidones) resulted in stable particles with higher grafting densities due to the compact size of each monomer unit. The higher grafting density also enabled an increase in the number of carbohydrates which can be installed per nanoparticle at the chain ends, and gave increased binding in a lectin recognition assay. These results will guide the development of new nanoparticle biosensors with enhanced specificity, affinity, and stability. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1200–1208     

Organoclays from alkaline-treated acid-activated clays

The cetyltrimethylammonium hydroxide (C16TMAOH) solution was proposed for the preparation of organoclays. Montmorillonite clay was acid activated at different acid/clay (a/c) (in mass) ratios, then treated with alkaline (sodium hydroxide) solution before being reacted with C16TMAOH solution. The acid activation caused a reduction in the number of cation exchange sites, and hence improved the exfoliation of the silicate sheets at higher pH values. The basal spacing increased significantly from 2.20 to 4.01 nm, and depended on the a/c ratios. The acid-activated clays with a/c ratios greater than 0.3 adsorbed significant amounts of C16TMA cations with a basal spacing of 4.01 nm compared with the non-acid-activated montmorillonite (2.51 nm). Meanwhile, the treatment of NaOH solution yielded clays with similar properties to that of the raw used clay. The XRF data, FT-IR, and ²⁹Si MAS-NMR techniques confirmed that the resulting amorphous silica during the acid activation was dissolved, and accompanied by a dramatical reduction in the surface areas. Similar amounts of C16TMA cations were adsorbed, i.e., close to 1 mmol g^?1, with a single basal spacing of 2.52 nm, independently of the treated acid-activated clays. The in-situ powder XRD studies revealed that an increase of the basal spacing to 4.20 nm was observed at intermediate temperatures ranging from 50 to 150 °C for organo-acid-activated clays with basal spacing of 4.01 nm, while a continuous decrease of the basal spacing was observed for organoclays with a basal spacing of 2.52 nm. At higher temperatures greater than 250 °C, the decomposition of the surfactant occurs, and the basal spacing decreases to a value of about 1.4 nm.     

Transient resonance Raman and density functional theory investigation of the chlorine atom/carbon disulfide molecular complex involved in selective alkane photochlorination reactions

The structure and bonding of the chlorine atom/carbon disulfide (CS(2)/Cl) complex involved in selective photochlorination reactions with alkanes was directly probed using transient resonance Raman spectroscopy. The experimental Raman vibrational frequencies were compared to those computed from density functional theory calculations for probable structures of the CS(2)/Cl complex. Our results indicate that the S [double bond] C [double bond] S...Cl complex species is responsible for the approximately 370 nm transient absorption band observed after ultraviolet photolysis of CCl(4) in the presence of CS(2). We discuss the structure and properties of the S [double bond] C [double bond] S...Cl complex and compare them with those for the related benzene/Cl and pyridine/Cl complexes.     

Development and test of an L-band magnetron

An L-band relativistic magnetron has been designed, built, and tested at approximately 1.1 GHz. The authors have obtained a peak RMS power of 2.4 GW in one waveguide, and a total of 3.6 GW from two waveguides. The overall efficiency reached 9%, compared with the input power. In contrast with previous S- and X-band magnetron results, the L-band magnetron impedance does not collapse at the end of the pulse, and microwave generation tends to last as long as high voltage is applied. This implies that large total energies can be produced by applying long high-voltage pulses     

Beiträge zur chemie des bors LX zur reaktion von borhalogeniden mit trimethyl-stannyldiphenylphosphin-metall-pentacarbonylen: Methylhalogenstannyldiphenylphosphin-metall-pentacarbonyle

The stannylphosphine-metal pentacarbonyls (CO)₅M·PPh₂SnMe₃ (M = Cr, Mo, W) methylate BCl₃ and yield the monochloro compounds (CO)₅M·PPh₂SnMe₂Cl. However, up to two of the methyl groups are replaced during the reaction with BBr₃ in benzene solution, the products being (CO)₅M·PPh₂SnMe₂Br and (CO)₅M·PPh₂SnMeBr₂.     

Effects of silicone acrylate on morphology, kinetics, and surface composition of photopolymerized acrylate mixtures

Films (ca. 150 microm thick) of twelve acrylate mixtures, which contained various proportions of hydrocarbon acrylates [mainly oligo(ethylene glycol) diacrylate, (OEGDA)] and small amounts of a silicone hexaacrylate (in proportion of 5% or less), were cured on a nickel substrate, and X-ray photoelectron spectroscopy analysis of the nickel-side surface compositions showed that for formulations with and without the silicone hexaacrylate, this surface was enriched with OEGDA and saturated (up to 50%) with the silicone hexaacrylate, respectively. The silicone hexaacrylate phase-separated and formed micelles which migrated to the resin-nickel interface. Silicone hexaacrylate, inherently less reactive, also significantly slowed the photopolymerization of the mixtures. The sequential homopolymerization of OEGDA and silicone hexaacrylate in a formulation was elicited using real-time Fourier transform infrared spectroscopy. The design-of-experiment approach was used to quantify the influence of the components on gelation time and the nickel-side surface composition as well as provide the statistical models to predict these two properties for new compositions.