Cyclotrimerization of ‘Oxabenzonorbornadiene’: Synthesis of syn‐ and anti‐5,6,11,12,17,18‐Hexahydro‐5,18:6,11:12,17‐triepoxytrinaphthylene

An efficient synthetic route to the concave‐shaped, potentially ionophoric syn‐ and anti‐isomers of 5,6,11,12,17,18‐hexahydro‐5,18:6,11:12,17‐triepoxytrinaphthylene ( 4 ) was elaborated. Starting from ‘oxabenzonorbornadiene’ ( 5 ), the stannylated precursor 9 was prepared in three steps, followed by cyclotrimerization catalyzed by copper(I) thiophene‐2‐carboxylate (CuTC) , which afforded 4 in a syn/anti ratio of 5 : 4.     

2,7,12,17‐Tetraoxa‐3,4:5,6:13,14:15,16‐tetrabenzo­dispiro­[8.1.8.0]­nona­decane

The reaction of bi­phenyl‐2,2′‐diol with 1,1,2,2‐tetrakis­(bromo­methyl)­cyclo­propane leads to two products, namely a propellane‐type compound and a di­spiro‐type compound. The molecular structure of 4,5;6,7‐dibenzo‐3,8,12‐tri­oxa[8.3.1]­propellane has been determined previously by spectroscopic methods. The crystal structure of the di­spiro product, 2,7,12,17‐tetraoxa‐3,4:5,6:13,14:15,16‐tetrabenzodi­spiro[8.1.8.0]­nona­decane, C₃₁H₂₆O₄, revealed that the conformations of the nine‐membered heterocyclic rings are due to interactions between the π‐electron system of the bi­phenyl moiety and the lone electron pairs of the ether O atoms, the repulsion of the lone electron pairs of atoms O1⃛O2 and O3⃛O4, and steric interactions between H atoms in ortho positions. The conformations have C₁ symmetry and can be described approximately as twist‐boat.     

First Sino‐German Symposium: «Frontiers of Chemistry»

60 young scientists from China and Germany followed the joint invitation of the Chinese Chemical Society (CCS) and the GDCh to attend the First Sino‐German Symposium “Frontiers in Chemistry”. 36 lectures and 25 posters covering all aspects of chemistry in combination with the scenery of the old Seeon monastery created an ideal atmosphere to overcome cultural and language problems and to foster contacts between young researchers of both countries.     

Characterization of LaBr<Subscript>3</Subscript>: Ce and LaCl<Subscript>3</Subscript>: Ce scintillators for gamma-ray spectroscopy

This study aims to investigate the performance of relatively new cerium-doped scintillators, LaCl₃ and LaBr₃, for gamma-ray spectroscopy. The study involved recording of detected spectra and measurement of energy resolution, as well as photo-fraction. The Monte Carlo package, GATE, was used to validate the experiments. In general, the energy resolution figures achieved were twice as good as that of NaI(Tl). In conclusion, LaBr₃: Ce and LaCl₃: Ce crystals have excellent energy resolution, (2.13±0.03)% and (2.92±0.04)% at 1332 keV, respectively, and comparable photo-fraction to NaI(Tl). Hence, these crystals, particularly LaBr₃: Ce, have the potential to replace NaI(Tl) as the scintillator of choice for γ-ray spectroscopy.     

Bromination of ‘endo‐Benzocyclobutanorbornene': Synthesis of ‘endo‐ 11,12‐Dibromobenzocyclobutanorbornene': High‐Temperature Bromination,Part XIV

The electrophilic addition of Br to ‘endo‐benzocyclobutanorbornene' 5 at −50° led in high yield to the formation of the rearranged dibromides 6 and 7 . However, high‐temperature bromination of 5 in decalin at 150° gave exclusively nonrearranged product 8 in 98% yield. From the elimination of nonrearranged product 8 , ‘endo‐bromobenzocyclobutanorbornene' 9 and ‘endo‐benzocyclobutanorbornene' 5 were obtained. Similarly, bromination of monobromide 9 at 77° yielded the nonrearranged tribromide 12 in quantitative yield. The dehydrobromination of 12 provided the ‘endo 11,12‐dibromobenzocyclobutanorbornene' 3 in high yield, which is a synthon for the trimerization reactions.     

In situ Detection of Microplastics: Single Microparticle‐electrode Impacts

Particle‐impact electrochemistry is employed to study spherical polyethylene microparticles suspended in an aqueous solution. This electrochemical method detects polyethylene microparticles impacting on a carbon fiber electrode generating a transient current response or “spike”. We interpret the physio‐chemical origin of the spikes and accurately identify particle size distributions and concentrations for microparticles of sizes 1–10 μm.     

The effect of pH ont he thermal stability of<span style='font-size:10.0pt;font-family:"SymbolProp BT";mso-bidi-font-family:"SymbolProp BT"'>a-actin isoforms

Summary The effect of pH was characterised on the thermal stability of magnesium saturated skeletal and cardiac α-actin isoforms with differential scanning calorimetry (DSC) at pH 7.0 and 8.0. The calorimetric curves were further analysed to calculate the enthalpy and transition entropy changes. The activation energy was also determined to describe the energy consumption of the initiation of the thermal denaturation process. Although the difference in T_mvalues is too small to interpret the difference between the a-actin isoforms, the values of the activation energy indicated that the α-skeletal actin is probably more stable compared to the α-cardiac actin. The difference in the activation energies indicated that lowering the pH can produce a more stable protein matrix in both cases of the isoforms. The larger range of the difference in the values of the activation energies suggested that the α-cardiac actin is probably more sensitive to the change of the pH compared to the α -skeletal actin.     

Modeling and optimizing toughness and rigidity of PA6/SBR: Using compatibilizer and response surface methodology

The improvement of miscibility between toughened Polyamide-6 (PA6) and Styrene-Butadiene Rubber (SBR) was carried out using grafted Glycidyl Methacrylate (SBR-g-GMA). At first, the compatibilizers were prepared using different comonomers, Styrene, and N-vinyl pyrrolidone. Central composited design (CCD) was distinctly applied to study the influence of Glycidyl Methacrylate (GMA) content and comonomer/GMA on the process of compatibilizer preparation. Four models were developed for Gel content and Degree of grafting for both comonomers using Design-expert software. The models were used to calculate the optimum operating conditions and according to the Flory-Huggins parameter and obtained results, SBR-co-NVP-g-GMA was chosen as an effective compatibilizer. Afterward, another CCD was employed to scrutinize the effect of various amounts and grafting degree of compatibilizer on morphology and mechanical properties of PA6/SBR. The Interparticle distance and polydispersity were studied using a Scanning electron microscope (SEM) and also the Izod impact test inspected in order to evaluate the mechanical properties. Finally, modulus and impact strength were optimized to minimize the former and maximize the latter. Also, the most practical terms in the fitted model are statistically specified using F-value. The root causes for the improvement of blend properties were attributed to a chemical reaction between epoxy groups in SBR-g-GMA and both the carboxylic and amine groups in PA6. Impact strength (539.8 J/m) and modulus (2017.2 N/mm²) of the optimum blend indicate an excellent agreement with the amounts predicted by the models.     

3′:5′‐Cyclic nucleotides: two sodium salts of cdTMP

3′:5′‐Cyclic nucleotides play an outstanding role in signal transduction at the cellular level but, in spite of comprehensive knowledge of the biological role of cyclic nucleotides, their structures are not established fully. Two hydrated sodium salts of thymidine 3′:5′‐cyclic phosphate (cdTMP, C₁₀H₁₂N₂O₇P), namely sodium thymidine 3′:5′‐cyclic phosphate heptahydrate, Na⁺·C₁₀H₁₂N₂O₇P⁻·7H₂O or Na(cdTMP)·7H₂O, (I), and sodium thymidine 3′:5′‐cyclic phosphate 3.7‐hydrate, Na⁺·C₁₀H₁₂N₂O₇P⁻·3.7H₂O or Na(cdTMP)·3.7H₂O, (II), have been obtained in crystalline form and structurally characterized, revealing one nucleotide in the asymmetric unit of (I) and eight different nucleotides in (II). All the cyclic nucleotide anions adopt a similar conformation with regard to nucleobase orientation, sugar conformation and 1,3,2‐dioxaphosphorinane ring puckering. In (I), no direct inter‐nucleotide hydrogen bonds are present, and adjacent nucleotide anions interact via water‐mediated and Na⁺‐mediated contacts. In contrast, in (II), direct thymine–phosphate N—H...O inter‐nucleotide hydrogen bonds occur and these are assisted by numerous inter‐nucleotide C—H...O contacts, giving rise to the self‐assembly of cdTMP⁻ anions into three different ribbons. Two of these three ribbons run in the same direction, while the third is antiparallel.     

1:1 Complexes of 2,3,5,6‐tetrachloro­benzene‐1,4‐dicarbonitrile with pyrene and phenanthrene: pseudo‐isomorphs

2,3,5,6‐Tetra­chloro­benzene‐1,4‐dicarbonitrile forms alternate π‐stacked 1:1 complexes with pyrene, C₈Cl₄N₂·C₁₆H₁₀, and phenanthrene, C₈Cl₄N₂·C₁₄H₁₀. These complexes are pseudo‐isomorphs. Phenanthrene, disordered about a centre of symmetry, takes the position of the pyrene, which sits exactly on this centre of inversion. The tetra­chloro­benzene­di­car­bo­nitrile mol­ecules in each complex also sit on centres of inversion and are in similar positions within the unit cells in the two structures, except that the orientation of the nitrile groups differs between the two.     

“蒸馏酒”还是“发酵酒”——对《科学史导论》中“spirits” 和“distillation”的再思考

科学史奠基者乔治·萨顿在《科学史导论》第二卷的第一部分对我国宋代酿酒著作《北山酒经》予以了简要描述,出现了“spirits”“distillation”等字样;而《北山酒经》被众多学者认为其描述对象是发酵酒(黄酒)。本文从东西方蒸馏技术和相关著作的文本分析对《科学史导论》中提及的蒸馏技术和蒸馏酒存在的可能性提出了质疑。