Reaction Of Bis Research Articles

Synthesis and Reactivity of Aluminum Disilacyclopropenes. Cyclic AlSi2 Delocalized 2π Systems.

The synthesis, structures, and reactivity of the first unsaturated AlSi2 three-membered ring systems were described. Reactions of dilithiodisilene [(NHB)LiSi═SiLi(NHB)] (1, NHB = diazaborolyl) with aluminum halides AlCl3, Ar(SiMe3)NAlCl2 (Ar = 2,6-iPr2C6H3), Cp*AlBr2 (Cp* = C5Me5), and TipAlBr2·Et2O (Tip = 2,4,6-iPr3C6H2) led to the formation of AlSi2 three-membered ring species, solvated (NHBSi)2AlCl(OEt2) (2) and solvent-free (NHBSi)2AlN(SiMe3) Ar (3), (NHBSi)2AlCp* (4), and (NHBSi)2AlTip (5), in good yields. X-ray diffraction studies and DFT calculations disclosed delocalized AlSi2 2π electron systems. Methanolysis of 4a resulted in cleavage of the Al-Si σ and Si-Si π bonds, giving trihydrodisilane (NHB)H(MeO)SiSiH2 (NHB) (6). Reaction of 4b with 4 equiv of N2O and H2C═CH2 resulted in the insertion of four oxygen atoms and four H2C═CH2 π bonds into all of the Al-Si and Si-Si bonds, yielding the O- and CH2CH2-bridged polycyclic species 7 and 8, demonstrating the synergistic reactivity of the Al-Si and Si-Si bonds in the AlSi2 ring system.

Synthesis and Characterization of Polyazothiazole and Polyacetyltetrazine from Novel Bis-Ketohydrazonoyl Dichlorides

The present work describes the preparation and characterization of new polyazothiazole and polyacetyltrazine polymers in good yields from new bis-(α-ketohydrazonoyl) dichlorides. Synthesis of the new polyazothiazole proceeds through the reaction of bis-(α-ketohydrazonoyl) dichlorides with 1,4-phenylene[bis(carbothioamide)] in a basic medium to afford novel polyazothiazole derivatives. Additionally, the self-polymerization reaction to synthesize polydiacetyltetrazine derivatives based on bis-(α-ketohydrazonoyl) dichlorides is described. The new polyazothiazole and polyacetyltetrazine derivatives were characterized using spectral and thermal techniques.

Lewis Acid-Base Adducts of α-Amino Acid-Derived Silaheterocycles and N-Methylimidazole

In chloroform solution, the reaction of bis(tert-butylamino)dimethylsilane ((tBuNH)2SiMe2) and an α-amino acid (α-amino isobutyric acid, H2Aib; D-phenylglycine, H2Phg; L-valine, H2Val) in the presence of N-methylimidazole (NMI) gave rise to the formation of the pentacoordinate silicon complexes (Aib)SiMe2-NMI, (Phg)SiMe2-NMI and (Val)SiMe2-NMI, respectively. Therein, the amino acid building block was a di-anionic bidentate chelator at the silicon atom. In solution, the complexes were involved in rapid coordination–dissociation equilibria between the pentacoordinate Si complex (e.g., (Aib)SiMe2-NMI) and its constituents NMI and a five-membered silaheterocycle (e.g., (Aib)SiMe2), as shown by 29Si NMR spectroscopy. The energetics of the Lewis acid-base adduct formation and the competing solvation of the NMI molecule by chloroform were assessed with the aid of computational methods. In CDCl3 solution, deuteration of the silaheterocycle NH group proceeded rapidly, with more than 50% conversion within two days. Upon cooling to −44 °C, the chloroform solvates of the adducts (Aib)SiMe2-NMI and (Phg)SiMe2-NMI crystallized from their parent solutions and allowed for their single-crystal X-ray diffraction analyses. In both cases, the Si atom was situated in a distorted trigonal bipyramidal coordination sphere with equatorial Si–C bonds and an equatorial Si–N bond (the one of the silaheterocycle). The axial positions were occupied by a carboxylate O atom of the silaheterocycle and the NMI ligand’s donor-N-atom.

Synthesis of Two Isomers of pyrido/benzo[b][1,4]selenazines: A Selective Catalyst‐Dependent Formation of C−N and C‐Se Bonds

AbstractThis work describes the selective synthesis of a series of pyrido/benzo‐fused 1,4‐selenazines, through the reaction of bis(3‐amino‐2‐pyridyl) or bis(2‐aminophenyl) diselenides with different β‐dicarbonyl compounds. When molecular I2 was used as catalyst, a series of (Z)‐1‐(1H‐pyrido[2,3‐b][1,4]selenazin‐2(3H)‐ylidene)propan‐2‐ones were obtained. On the other hand, in the absence of catalyst, 1‐(2‐methyl‐1H‐pyrido[2,3‐b][1,4]selenazin‐3‐yl)ethan‐1‐ones could be prepared selectively. The structure of the prepared compounds was elucidated by NMR and HRMS analysis and confirmed by single crystal X‐ray diffraction. The versatility of the protocol was demonstrated not only by the access to a variety of 1,4‐selenazine derivatives, but also by the structural diversity in the 1,3‐dicarbonyl precursors, incorporating multifunctionalities in the synthesized heterocycles.

Collective Acceleration of Helium Ions from Its Residual Atmosphere in a Luce Diode

The collective acceleration of helium ions from its residual atmosphere in the Luce diode was studied at helium pressures from 0.13 to 0.23 Pa. The energy of accelerated ions was determined from the drift velocity of the virtual cathode accelerating the ions. The number of 4He was determined by radioactivities of 13N and 30P induced in h-BN and Al targets via the nuclear reactions 10B(α,n)13N and 27Al(α,n)30P. The efficiency of capturing 4He ions in collective acceleration from the residual helium atmosphere was estimated as 0.25%. With increasing helium pressure above 0.15 Pa, the energy of the main ion group noticeably decreased to 0.46 MeV/amu compared to the acceleration from a usual residual atmosphere (~0.6 MeV/amu); however, the probability of ion acceleration to a specific energy of up to 1.57 MeV/amu increased significantly. Such increases in the ion energy were accompanied by the appearance of the signal of the second virtual cathode 7–9 ns after the appearance of the first virtual cathode.

Ab initio investigations of A=8 nuclei: α–α scattering, deformation in 8He, radiative capture of protons on 7Be and 7Li and the X17 boson

We apply the No-Core Shell Model with Continuum (NCSMC) that is capable of describing both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. The NCSMC can predict structure and dynamics of light nuclei and, by comparing to available experimental data, test the quality of chiral nuclear forces. We discuss applications of NCSMC to the α–α scattering and the structure of 8Be, the p+7Be and p+7Li radiative capture and the production of the hypothetical X17 boson claimed in ATOMKI experiments. The 7Be(p, γ)8B reaction plays a role in Solar nucleosynthesis and Solar neutrino physics and has been subject of numerous experimental investigations. We also highlight our investigation of the neutron rich exotic 8He that has been recently studied experimentally at TRIUMF with an unexpected deformation reported.

Ab initio informed evaluation of the radiative capture of protons on 7Be

The radiative capture of protons by 7Be, which is the source of 8B that β-decays emitting the majority of higher-energy solar neutrinos measured on earth, has not yet been measured at astrophysically relevant energies. The recommended value for its zero-energy S-factor, S17(0)=20.8±(0.7)exp±(1.4)theory eV⋅b, relies on theoretical extrapolations from higher-energy measurements, a process that leads to significant uncertainty. We performed a set of first-principle (or, ab initio) calculations of the 7Be(p,γ)8B reaction to provide an independent prediction of the low-energy S-factor with quantified uncertainties. We demonstrate underlying features in the predicted S-factor allowing the combination of theoretical calculations and measurements to produce an evaluated S-factor of S17(0)=19.8±0.3 eV⋅b. We expect the calculations and uncertainty quantification process described here to set a new standard for the evaluation of light-ion astrophysical reactions.

Multicomponent click reactions catalyzed by copper(I) complex bearing Bis(imino)pyridine-phosphine ligands

Copper(I)-bis(imino)pyridine-triphenylphosphine complex (2a) was prepared from the reaction of bis(imino)pyridine ligand and [Cu(PPh3)3Cl]. The tetracoordinated copper(I) complex was characterized by UV–Visible, NMR and elemental analysis. The molecular structure of 2a was characterized by single crystal X-ray diffraction and adopts a distorted tetrahedral geometry around the copper centre. The copper(I) 2a was established as catalyst for one-pot multicomponent Click reaction of aryl halides and sodium azide with terminal alkynes using 0.5 mol % catalyst loading in methanol as a solvent. Several 1,4-disubstituted 1,2,3-triazoles have been synthesized in moderate to excellent yields.

A non-fueled nuclear-heated rod for in-pile transient boiling studies

Separate-effects boiling experiments have recently been conducted in the Transient Reactor Test Facility at Idaho National Laboratory to investigate transient heating and irradiation effects on cladding-to-coolant heat transfer. Specifically, transient critical heat flux (CHF) remains an important area of research, and better understanding of this phenomenon has potential for improving predictive models related to operational and safety limits. Consequently, this knowledge is expected to improve efficiency of light-water reactor operations. A novel borated nuclear-heated rodlet (BNHR) was designed to enable observation of transient cladding-to-coolant heat transfer phenomena. The final BNHR design takes a surrogate approach, wherein nuclear heating is induced by 10B(n, α) reactions rather than derived from fissions in a fueled specimen. The structure of the BNHR consists of a hollowed out borated (Bnat ∼ 2.05 wt%) stainless steel tube with an hourglass-shaped outer surface, capped at both ends with non-borated stainless steel. This geometry allows for inner-rodlet instrumentation and generation of the highest nuclear heating rates near the center of the rodlet to ensure onset of boiling near instrumentation for real-time observation. A novel approach to measuring the nuclear energy deposition rate in the BNHR separate and apart from the influence of the coolant, termed the n-α thermometer, is also detailed in this paper. This device has demonstrated excellent repeatability, and measurements indicate predictive modeling results for energy deposition in the BNHR rod agree within a 10% margin of the experiment measurements. These results give confidence that the BNHR design has successfully met experiment objectives.

Synthesis of polyfluoroalkylphosphorylated dihydroquinolines and dihydroisoquinolines decorated with N-acylethenyl substituents by the reaction of bis(polyfluoroalkyl)phosphonates with electron-deficient acetylenes and quinolines

Dihydroquinolines and dihydroisoquinolines decorated with 2- or 4-polyfluoroalkylphosphoryl groups and N-acylethenyl, cyanoethenylphenyl substituents were synthesized in up to 91% yield via straightforward strategy including simultaneous catalyst- and solvent-free mild (room temperature, 0.2–20 h) N-ethenylation/C-phosphorylation of quinolines and isoquinolines with electron-deficient acetylene / bis(polyfluoroalkyl)phosphonate pairs. The structural interplay between 2 and 4-regioisomers was studied. The reaction with terminal acylacetylenes afforded N-acylethenyl-2-phosphoryl-1,2-dihydroquinolines of the E-configuration relative to the double bond. On the contrary, with cyanophenylacetylene, under similar conditions, a mixture of 1,2- and 1,4-regioisomers was formed (the N-ethenyl substituents having both the E- and Z-configuration) along with double phosphorylated bisadducts, 2,4-bis(polyfluoroalkylphosphoryl)-1,2,3,4-tetrahydro(iso)quinolines. The 1,4-isomers prove to be the thermodynamic products since they can be exclusively obtained by heating (70–75 °С) a mixture of 2- and 4-regioisomers. The synthesized compounds represent a new family of possible drug precursors.

Towards Understanding Incomplete Fusion Reactions at Low Beam Energies: Modified Sum Rule Model

We investigated the enhanced production of nuclei formed via incomplete fusion (ICF) reactions near and above the Coulomb barrier energies (5–8 MeV/A). The cross-sections of the evaporation residues formed in the reactions—11B+124Sn, 10B+124Sn and 11B+122Sn—were measured using off-line gamma-ray spectrometry. The sum rule model (SRM) by Wilczyński et al. predicted the cross-section values too low compared to our experimental results. In earlier studies, the same model has been very successful in explaining ICF reactions at high beam energies (>10 MeV/A). We, therefore, modified the SRM, specifically incorporating the energy dependence in the definition of critical angular momentum ℓcr. The resulting modified SRM gave an improved theoretical estimate for the reactions we studied.

Theoretical evaluation of solar proton-proton fusion reaction rate and its uncertainties

The weak proton-proton fusion into a deuteron (2H) is the driving reaction in the energy production in the Sun, as well as similar main sequence stars. Its reaction rate in the solar interior is determined only theoretically. Here, we provide a new determination of the rate of this reaction in solar conditions S11(0), and analyze theoretical and experimental sources for uncertainties, using effective field theory of Quantum Chromodynamics without explicit pions at next-to-leading order. This prediction procedure is verified and validated using experimentally measured set of electromagnetic reactions, which we show to be analogous in their operator structure and properties to the weak sector, and are reproduced within the assessed theoretical uncertainty, using the same approach. We find an enhancement of S11 by 1−4% over the previously recommended value. This change reduces the calculated fluxes of neutrinos originating in 8B and 7Be nuclear reactions in the Sun, thus favoring higher abundances for metallic photospheric elements, in the tension between different composition determination, known as the “Solar Composition Problem”.

Differential cross-section measurements for the 9Be(3He,3He0)9Be elastic scattering and the 9Be(3He,px)11B reactions

The differential cross sections of 9Be(3He,3He0)9Be elastic scattering and of the 9Be(3He,p0,1,2,3,4+5,6,7)11B reactions have been determined in the energy range from 1.6 to 6 MeV at six backward angles from 120° to 170°, with a step of 10°. The experiments were performed at the 4 MV Dynamitron Tandem Laboratory of the Central Unit for Ion Beams and Radionuclides of the Ruhr University Bochum in Germany. The obtained datasets have been validated through benchmarking experiments, at 8 beam energies, using a thick, high-purity, beryllium foil. The results of the present work are compared with existing ones from literature and any discrepancies observed are discussed.

Numerical Simulations of the Acceleration of Fast Protons and of the Excitation of Nuclear Reactions 11B(p, 3a) and 11B(p, n)C11 at the Intensities of Picosecond Laser Radiation in the Range 1018-1019 W/cm2

Results of numerical simulations for acceleration of proton beams at the irradiation of Al target by a superintense laser pulse are presented. There is a good agreement with the experimental data in a broad range of laser intensities from I = 1018 W/cm2 to I = 1019 W/cm2 at the fixed laser pulse duration. The obtained parameters of proton beams were used for calculation of the total yield of a particles and neutrons for the nuclear reactions 11B(p, 3a) and 11B(p, n)C11C at the collisions of proton beams with boron targets. It is shown that the number of a particles escaping boron target and arriving at track detectors is less than 5of the total amount of a particles, because the majority of these particles remain inside the target owing to ionization losses. The derived values of the yield ofparticles’ which arrive at detectors are in good agreement with the experimental data. We also calculate the total yield of neutrons in the reaction 11B(p, n)C11C. It is found that, at the intensity I = 1019 W/cm2 of the picosecond laser pulse, the yield is equal to Nn = 1.4 × 108 , this value is approximately of 3% of the total yield of a particles.

Radiation Limit for the Energy Gain of the p–11B Reaction

The feasibility of positive energy yield in systems with the p–11B reaction is considered here by considering refined (optimistic) data on the reaction rate. The analysis was carried out within the traditional framework for magnetic confinement systems, but without taking into account a particular type of plasma configuration. The energy balance was considered both for the ions and electrons. The balance of particles includes all species as well as the products of fusion (alpha particles). Calculations have shown that accounting for the content of thermalized reaction products (alpha particles) leads to an increase in radiation losses and a decrease in gain to Q < 1. In the steady-state scenario, the energy gain Q~5–10 can be obtained in p–11B plasma, if only the fast (high-energy) population of fusion alpha particles is considered. For pulsed modes, the gain value is proportional to the content of alpha particles, and it is limited by the complete burn of one of the fuel components (boron), so it does not exceed unity. In the analysis we did not rely on any assumptions about the theoretically predicted mechanisms for increasing the cross section and the reaction rate, and only radiation losses (primarily bremsstrahlung) dramatically affect the gain Q. Thus, the regimes found can be considered as limiting in the framework of the classical concepts of processes in hot fusion plasma.

Iodine(I) and Silver(I) Complexes Incorporating 3-Substituted Pyridines.

Building upon the first report of a 3-acetaminopyridine-based iodine(I) complex (1b) and its unexpected reactivity toward tBuOMe, several new 3-substituted iodine(I) complexes (2b-5b) have been synthesized. The iodine(I) complexes were synthesized from their analogous silver(I) complexes (2a-5a) via a silver(I) to iodine(I) cation exchange reaction, incorporating functionally related substituents as 3-acetaminopyridine in 1b; 3-acetylpyridine (3-Acpy; 2), 3-aminopyridine (3-NH2py; 3), and 3-dimethylaminopyridine (3-NMe2py; 4), as well as the strongly electron-withdrawing 3-cyanopyridine (3-CNpy; 5), to probe the possible limitations of iodine(I) complex formation. The individual properties of these rare examples of iodine(I) complexes incorporating 3-substituted pyridines are also compared to each other and contrasted to their 4-substituted counterparts which are more prevalent in the literature. While the reactivity of 1b toward etheric solvents could not be reproduced in any of the functionally related analogues synthesized herein, the reactivity of 1b was further expanded to a second etheric solvent. Reaction of bis(3-acetaminopyridine)iodine(I) (1b) and iPr2O gave [3-acetamido-1-(3-iodo-2-methylpentan-2-yl)pyridin-1-ium]PF6 (1d), which demonstrated potentially useful C-C and C-I bond formation under ambient conditions.

Response control of RPLGD for gamma-ray dose measurement using lead filters for BNCT

Boron Neutron Capture Therapy (BNCT) is a cell-selective radiotherapy using a neutron capture reaction of 10B. In recent years, Accelerator Based Neutron Sources (ABNS) are under development instead of nuclear reactors for the next-generation neutron irradiation system for BNCT. However, ABNS as well as nuclear reactor usually generates unavoidable secondary gamma-rays by neutron-nuclear reactions such as capture reaction. In this research, we aimed to develop a separate measurement method of only gamma-rays in a mixed field of neutrons and gamma-rays using a fluorescent glass dosimeter (RPLGD), because most dosimeters have sensitivity to both radiation types. For this purpose, we proposed a lead filter method using two RPLGDs and lead filters. However, this method has a problem that the sensitivity to low energy gamma-rays (∼100 keV) is very small. In order to improve the sensitivity to low energy gamma-rays, we devised a method using a specially shaped lead filter. From theoretical calculations, we have shown that it was possible to estimate the air dose rate of the field where the gamma-ray energy spectrum shape was known for energies up to 10 MeV. In addition, we produced the specially shaped lead filter and experimentally confirmed the validity of the lead filter method using several gamma-ray standard sources and by measurements in a nuclear fuel storage room.

Measurement of the applicability of various experimental materials in a medically relevant reactor neutron source part two: Study of H3BO3 and B-DTPA under neutron irradiation

Experiments related to Boron Neutron Capture Therapy (BNCT) accomplished at the Institute of Nuclear Techniques (INT), Budapest University of Technology and Economics (TUB) are presented. Relevant investigations are required before designing BNCT for vivo applications. Samples of relevant boron compounds (H3BO3, BDTPA) usually employed in BNCT were investigated with neutron beam. Channel #5 in the research reactor (100 kW) of INT-TUB provides the neutron beam. Boron samples are mounted on a carrier for neutron irradiation. The particle attenuation of several carrier materials was investigated, and the one with the lowest attenuation was selected. The effects of boron compound type, mass, and compound phase state were also investigated. To detect the emitted charged particles, a traditional ZnS(Ag) detector was employed. The neutron beam's interaction with the detector-detecting layer is investigated. Graphite (as a moderator) was employed to change the neutron beam's characteristics. The fast neutron beam was also thermalized by placing a portable fast neutron source in a paraffin container and irradiating the H3BO3. The obtained results suggest that the direct measurement approach appears to be insufficiently sensitive for determining the radiation dose committed by the Alpha particles from the 10B (n,α) reaction. As a result, a new approach must be used.

BN-Butafulvenes and Their Application in the Synthesis of Highly Substituted BN-9,1-Naphthalenes.

BN-butafulvenes, mono-BN isosteres of butafulvene and highly strained isomers of azaborines and B-amino boroles, have been synthesized via hydrolysis of the urana-borabicyclic complexes obtained from the reactions of bis(alkynyl)boranes with an uranacyclopropene complex. Their 4-dimethylaminopyridine (DMAP) adducts can further isomerize to 1,2,4,6-multisubstituted BN-9,1-naphthalenes. Both NMR reaction monitoring and theoretical calculations point to a reaction mechanism involving dearomative insertion of DMAP followed by two consecutive 1,2-hydrogen shifts. The photophysical studies of the highly substituted BN-9,1-naphthalenes reveal a notable redshift in both the UV-vis absorption and emission spectra. The (TD)-DFT calculations corroborate the experimental data, suggesting that the strong π-donating amino substitution at the 1- and/or 6-positions destabilizes the HOMO, and thus leading to a notable decrease of the HOMO-LUMO gap.

BN‐Butafulvene und ihre Anwendung in der Synthese von hochsubstituierten BN‐9,1‐Naphthalinen

AbstractBN‐Butafulvene, Mono‐BN‐Isostere von Butafulven und hochgespannte Isomere von Azaborinen und B‐Aminoborolen, wurden durch Hydrolyse der Urana‐Borabicyclus‐Komplexe synthetisiert, die aus der Reaktion von Bis(alkinyl)boranen mit einem Uranacyclopropen‐Komplex stammen. Ihre 4‐Dimethylaminopyridin (DMAP)‐Addukte können weiter zu 1,2,4,6‐multisubstituierten BN‐9,1‐Naphthalinen isomerisieren. Sowohl die NMR‐spektroskopische Reaktionsverfolgung als auch theoretische Berechnungen deuten auf einen Reaktionsmechanismus hin, der eine dearomative Insertion von DMAP gefolgt von zwei aufeinanderfolgenden 1,2‐Wasserstoffumlagerungen beinhaltet. Die photophysikalischen Untersuchungen der hochsubstituierten BN‐9,1‐Naphthaline zeigen eine bemerkenswerte Rotverschiebung, sowohl in den UV/Vis‐Absorptions‐ als auch in den Emissionsspektren. Die (TD)‐DFT‐Berechnungen bestätigen die experimentellen Daten und deuten darauf hin, dass die starke π‐donierende Aminosubstitution an den 1‐ und/oder 6‐Positionen das HOMO destabilisiert und somit zu einer bemerkenswerten Verringerung der HOMO–LUMO‐Lücke führt.