Search results for "Direct reaction"
showing 10 items of 14 documents
Intermolecular and Intramolecular Transamidation Reactions
2006
The amide functional group is resonance stabilised and direct reaction with amines is known to be difficult. Facile amide exchange reactions would enable the synthesis of important new amide based molecules, therefore transamidation reactions represent an important step in this direction. In order to ensure a transamidation reaction takes place, special requirements and conditions are required. According to the different structural characteristics of the carbox-amide group and types of activation, the most relevant examples of this reaction will be reviewed.
Half-sandwich complexes of molybdenum-(III), -(IV) and -(V) with P–O and P–N bifunctional ligands Ph2PCH2X (X = 2-oxazolinyl, or C(O)NPh2)
2000
International audience; The reaction of the ligands Ph2PCH2X (X = 2-oxazolinyl, I; or C(O)NPh2, II) with the half-sandwich molybdenum(III) precursors [Mo(η-C5R5)(μ-Cl)2]2 (R = H or Me) has been investigated. Ligand I reacts with both complexes to form the corresponding adducts [Mo(η-C5R5)Cl2(Ph2PCH2C3H4NO)] (R = H, 1; or Me, 2). The reaction between I and [MoCp*Cl4] (Cp* = η-C5Me5) affords [MoCp*Cl4(Ph2PCH2C3H4NO-κ1P)] as a kinetic isomer, which then transforms quantitatively to [MoCp*Cl3(Ph2PCH2C3H4NO-κ2P,N)]+Cl−, 3. Ligand II reacts with [MoCp(μ-Cl)2]2 (Cp = η-C5H5) to afford the adduct [CpMoCl2{Ph2PCH2C(O)NPh2-κ2P,O}], 4, as an equilibrium mixture of two isomers. Longer reaction times in…
Tetranitroresorcin[4]arene: synthesis and structure of a new stereoisomer
2009
The direct reaction between 2-nitroresorcinol and acetaldehyde in alkaline medium yields tetranitro-C1-resorcin[4]arene in a moderate 8.2% overall yield which was characterized by single crystal X-ray crystallography, 1H NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS). In solution and in the solid state, the product adopts a unique, thermally stable and unprecedented rcct-boat conformation.
Cost efficient preparation of lead aminoalkoxides directly from lead(II) oxide
2005
Abstract The preparation of lead(II) aminoalkoxides has been demonstrated from the direct reaction of aminoalcohols with lead(II) oxide. The denticity of the aminoalcohols determined the facility of the reactions, the rate increasing with the number of hydroxyls. Thus, [Pb(dmae)2], 1, [Pb(mdea)]∞, 2, and [Pb(teaH)]2, 3 (dmaeH = dimethylaminoethanol, mdeaH2 = N-methyldiethanolamine, and teaH3 = triethanolamine) have been prepared in high yields and characterized by 1H and 13C NMR. The X-ray crystal structure analyses of 2 and 3 are described.
Syntheses, Structures, and Properties of New Quaternary Gold-Chalcogenides: K2Au2Ge2S6, K2Au2Sn2Se6, and Cs2Au2SnS4
1998
The new compounds K2Au2Ge2S6 (1), K2Au2Sn2Se6 (2), and Cs2Au2SnS4 (3) have been synthesized through direct reaction of the elements with a molten polyalkalithiogermanate(stannate) flux at 650, 550, and 400 °C, respectively. Their crystal structures have been determined by single crystal X-ray diffraction techniques. 1 crystallizes in the monoclinic space group P21/n with a = 10.633(2) A, b = 11.127(2) A, c = 11.303(2) A, β = 115,37(3)°, V = 1208,2(3) A3 and Z = 4, final R(Rw) = 0.045(0.106). 2 crystallizes in the tetragonal space group P4/mcc with a = 8.251(1) A, c = 19.961(4) A, V = 1358,9(4) A3 and Z = 4, final R(Rw) = 0.040(0.076). 3 crystallizes in the orthorhombic space group Fddd with…
Study of isomeric states in $^{198,200,202,206}$Pb and $^{206}$Hg populated in fragmentation reactions
2018
International audience; Isomeric states in isotopes in the vicinity of doubly-magic 208Pb were populatedfollowing reactions of a relativistic 208Pb primary beam impinging on a9Be fragmentation target. Secondary beams of 198,200,202,206Pb and 206Hg wereisotopically separated and implanted in a passive stopper positioned in thefocal plane of the GSI Fragment Separator. Delayed γ rays were detected withthe Advanced Gamma Tracking Array (AGATA). Decay schemes were reevaluatedand interpreted with shell-model calculations. The momentumdependentpopulation of isomeric states in the two-nucleon hole nuclei206Pb/206Hg was found to differ from the population of multi neutron-holeisomeric states in 198…
Direct neutron capture for magic-shell nuclei.
1995
In neutron capture for magic--shell nuclei the direct reaction mechanism can be important and may even dominate. As an example we investigated the reaction $^{48}$Ca(n,$\gamma)^{49}$Ca for projectile energies below 250\,keV in a direct capture model using the folding procedure for optical and bound state potentials. The obtained theoretical cross sections are in agreement with the experimental data showing the dominance of the direct reaction mechanism in this case. The above method was also used to calculate the cross section for $^{50}$Ca(n,$\gamma)^{51}$Ca.
Microscopic Study of Pionic Atoms and Methods of Production
1992
We have constructed a theoretical optical potential for pionic atoms and low energy pions based on the first and second order terms of a many body expansion on the number of ph excitations. The new density dependence of the potential produces notoriously improved results in the problem of the anomalies. On the other hand we have separated the different contributions to the imaginary part of the potential and relate them to the different reaction channels, quasielastic and absorption. The agreement with the data for different channels, energies and nuclei is rather good with some isolated discrepancies. With this potential we have also investigated the deeply bound pionic states in heavy nuc…
New Insight into the Cluster Structure of $^9$Be by Reactions with Deuteron Beam
2018
International audience; Angular distributions of protons, deuterons, tritons, and alpha particles emitted in the reaction 2H+9Be at Elab=19.5, 25, and 35 MeV were measured to study the structure of 9Be, especially to shed light on the internal clusters and possible cluster transfer of 5He. The experiments were performed at sufficiently high energies to ensure suppression of compound nucleus contribution. Thus, the direct reaction mechanism should be mainly responsible for the measured five-nucleon transfer cross section. The analysis suggests a significant contribution of simultaneous five-nucleon transfer in the reaction channel 9Be (d,4He) 7Li.
Neutron halos in the excited states of B12
2018
The differential cross sections of the $^{11}\mathrm{B}(d,p)\phantom{\rule{0.16em}{0ex}}^{12}\mathrm{B}$ reaction leading to formation of the ${1}^{+}$ ground state and the 0.95-MeV ${2}^{+}$, 1.67-MeV ${2}^{\ensuremath{-}}$, 2.62-MeV ${1}^{\ensuremath{-}}$, 2.72-MeV ${0}^{+}$, and 3.39-MeV ${3}^{\ensuremath{-}}$ excited states of $^{12}\mathrm{B}$ are measured at ${E}_{d}$ = 21.5 MeV. The analysis of the data is carried out within the coupled-reaction-channels method for the direct neutron transfer and the Hauser-Feshbach formalism of the statistical compound-nucleus model. The spectroscopic factors, asymptotic normalization coefficients, and rms radii of the last neutron in all states stu…