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81.
Résumé Tout d'abord, on montre par RPE que le radical CH2=-CN possède à basse température une structure instable pliée et à température plus élevée une structure stable linéaire. Un calcul théorique sur ce radical ainsi que sur le radical butatriényle est en bon accord avec les résultats expérimentaux.
The structure of the Cyano-Vinyl Radical CH2=-CN experimental and theoretical study
First, it is shown by ESR that the radical CH2=-CN at low temperature presents an unstable bent structure and at higher temperature a stable linear structure. A theoretical calculation on this radical and on the butatrienyl one is in good agreement with the experimental results.
Zusammenfassung Aus ESR Messungen wird gefolgert, daß das Radikal CH2=-CN bei tiefer Temperatur in einer instabilen gebogenen Struktur und bei höherer Temperatur in einer stabilen linearen Struktur vorliegt. Theoretische Berechnungen stehen sowohl für dieses als auch für das Butatrienyl-Radikal in guter Übereinstimmung mit experimentellen Daten.相似文献
82.
3,3-Dichlorotricyclo[5.1.0.01,4]oct-5-en-2-one () was prepared by addition of dichloroketene to 1,3-cyclohexadiene followed by allylic bromination and dehydrobromination. 相似文献
83.
Louis Burnelle 《Theoretical chemistry accounts》1964,2(2):177-180
The function (M), which measures the effect of the bond formation on the electron density distribution, has been calculated for HCN and C2N2. The charge build up in the CN bonds is found to be quite the same in both molecules, which indicates that the outer bonds of C2N2 are practically unaffected by conjugation.
We are thankful to Miss Cl. Litt for programming the calculation of the function and to Mrs. M. Henseval for drawing the density contours. 相似文献
Zusammenfassung Die Funktion (M), ein Maß für die Änderung der Elektronendichteverteilung durch Bildung von Bindungen, wurde für HCN und C2N2 berechnet. Danach ist die Ladungsanhäufung in den CN-Bindungen für beide Moleküle praktisch gleich, was darauf hinweist, daß die äußeren Bindungen im C2N2 durch die Konjugation kaum verändert werden.
Résumé La fonction (M), qui mesure l'effet de la formation des liaisons sur la distribution de la densité électronique, a été calculée pour HCN et C2N2. D'après les calculs, l'accumulation de charge dans les liaisons CN est pratiquement la même dans les deux molécules, ce qui indique que les liaisons extérieures de C2N2 ne sont en fait pas affectées par la conjugaison.
We are thankful to Miss Cl. Litt for programming the calculation of the function and to Mrs. M. Henseval for drawing the density contours. 相似文献
84.
Starting from 2-amino-3-bromo-9-oxofluorene and from 3-methylfluorene respectively the preparation of 3-bromo-9-oxofluorene-2-carboxylic acid and of 2-bromo-9-oxofluorene-3-carboxylic acid is described. A synthesis of 3-bromo-4-methyl-9-oxofluorene is also given. 相似文献
85.
Liane M. Moreau Alexandre Herve Mark D. Straub Dominic R. Russo Rebecca J. Abergel Selim Alayoglu John Arnold Augustin Braun Gauthier J. P. Deblonde Yangdongling Liu Trevor D. Lohrey Daniel T. Olive Yusen Qiao Julian A. Rees David K. Shuh Simon J. Teat Corwin H. Booth Stefan G. Minasian 《Chemical science》2020,11(18):4648
We report the structural properties of ultra-small ThO2 and UO2 nanoparticles (NPs), which were synthesized without strong binding surface ligands by employing a covalent organic framework (COF-5) as an inert template. The resultant NPs were used to observe how structural properties are affected by decreasing grain size within bulk actinide oxides, which has implications for understanding the behavior of nuclear fuel materials. Through a comprehensive characterization strategy, we gain insight regarding how structure at the NP surface differs from the interior. Characterization using electron microscopy and small-angle X-ray scattering indicates that growth of the ThO2 and UO2 NPs was confined by the pores of the COF template, resulting in sub-3 nm particles. X-ray absorption fine structure spectroscopy results indicate that the NPs are best described as ThO2 and UO2 materials with unpassivated surfaces. The surface layers of these particles compensate for high surface energy by exhibiting a broader distribution of Th–O and U–O bond distances despite retaining average bond lengths that are characteristic of bulk ThO2 and UO2. The combined synthesis and physical characterization efforts provide a detailed picture of actinide oxide structure at the nanoscale, which remains highly underexplored compared to transition metal counterparts.ThO2 and UO2 nanoparticles synthesized using a COF-5 template exhibit unpassivated surfaces and provide insight into nanoscale properties of actinides. 相似文献
86.
Bakker MJ Vergeer FW Hartl F Rosa P Ricard L Le Floch P Calhorda MJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(7):1741-1752
Herein we describe in detail the bonding properties and electrochemical behavior of the first known triosmium carbonyl clusters with a coordinated redox-active ligand 4,4',5,5'-tetramethyl-2,2'-biphosphinine (tmbp), the phosphorus derivative of 2,2'-bipyridine. The clusters investigated were [Os(3)(CO)(10)(tmbp)] (1) and its derivative [Os(3)(CO)(9)(PPh(3))(tmbp)] (2). The crystal structures of both clusters are compared with those of relevant compounds; they served as the basis for density functional theory (DFT and time-dependent DFT) calculations. The experimental and theoretical data reveal an unexpected and unprecedented bridging coordination mode of tmbp, with each P atom bridging two metal atoms. The tmbp ligand is formally reduced by transfer of two electrons from the triangular cluster core that consequently lacks one of the metal-metal bonds. Both 1 and 2 therefore represent 50e(-) clusters with a coordinated 8e(-) donor, [tmbp](2-). The HOMO and LUMO of 1 and 2 possess a predominant contribution from different pi*(tmbp) orbitals, implying that the lowest energy excited state possesses a significant intraligand character. This is in agreement with the photostability of these clusters. DFT calculations also predict the experimentally observed structure of 1 to be the most stable one in a series of several plausible structural isomers. Stepwise two-electron electrochemical reduction of 1 and 2 results in dissociation of CO and PPh(3), respectively, and formation of the [Os(3)(CO)(9)(tmbp)](2-) ion. The initially produced radical anions of the parent clusters, in which the odd electron is predominantly localized on the tmbp ligand, are sufficiently stable at low temperatures and can be observed with IR spectroelectrochemistry. The electron-deficiency of the cluster core in 1 permits facile electrocatalytic substitution of a CO ligand by tertiary phosphane and phosphite donors. 相似文献
87.
Daniel Ammann Ren Bissig Marc Güggi Ern Pretsch Wilhelm Simon Irving J. Borowitz Louis Weiss 《Helvetica chimica acta》1975,58(6):1535-1548
The preparation of a series of non-cyclic, uncharged ligands able to selectively complex alkali and alkaline earth metal cations is described. These molecules are designed to be used as carriers for cations through membranes. Some of the compounds show high Ca2+ and Na+ selectivity, respectively, in liquid membrane electrodes. 相似文献
88.
Résumé La structure et le spectre électronique du fluoroacétylène et du chloroacétylène ont été étudiés à l'aide d'une méthode matricielle du type LCAO SCF MO où les fonctions monoélectroniques sont des orbitales orthogonalisées de Löwdin. Le transfert de charge de l'halogène au système est d'environ 0,04 électron 2p pour le fluor et 0,08 électron 3p pour le chlore. L'étude des transitions électroniques indique pour la transition du type - située vers 1850 Å un effet bathochrome et une augmentation de la force oscillatrice lorsque l'électronégativité de l'halogène décroît. Ceci permet d'identifier la transition située vers de plus grandes longueurs d'onde avec une transition -
dont la force oscillatrice varie en sens inverse de celle de la transition -.
Nous tenons à remercier Monsieur Berthier pour de nombreuses discussions sur ce travail, Messieurs Romanet et Wojtkowiak pour avoir attiré notre attention sur les problèmes posés par les spectres ultraviolets des halogéno-acétyléniques et Monsieur H. v. Hirschhausen pour nous avoir signalé une erreur numérique dans la fin de cet article. 相似文献
The electronic structure and spectra of fluoroacetylene and chloroacétylène have been studied by a matricial method of LCAO SCF MO type where the monoelectronic functions are Löwdin'S orthogonalized orbitals. The charge transfer from the halogen to the system is equal to about 0,04 2p electron for fluorine and to 0,08 3p electron for chlorine. A bathochromic effect and an increase of the oscillator strength with the halogen electronegativity decreasing have been found for the - transition at 1850 Å; from the theoretical results it is possible to identify the transition of lower energy as a - transition whose oscillator strength varies the other way than that of the - transition.
Zusammenfassung Struktur und Elektronenspektren von Fluor- und Chloracetylen wurden mit Hilfe einer Matrizenmethode vom LCAO-SCF-MO-Typ untersucht, wobei die Einelektronenfunktionen nach Löwdin orthogonalisiert wurden. Der Ladungsübergang vom Halogen zum -System entspricht etwa 0,04 2p-Elektronen bei Fluor und 0,08 3p-Elektronen bei Chlor. Für den --Übergang um 1850 Å wird für abnehmende Elektronegativität des Halogens eine bathochrome Verschiebung und eine Zunahme der Oscillatorenstärke gefunden. Das erlaubt, die längerwellige Bande einem - -Übergang zuzuordnen, dessen Oscillatorenstärke sich in entgegengesetzter Richtung ändert.
Nous tenons à remercier Monsieur Berthier pour de nombreuses discussions sur ce travail, Messieurs Romanet et Wojtkowiak pour avoir attiré notre attention sur les problèmes posés par les spectres ultraviolets des halogéno-acétyléniques et Monsieur H. v. Hirschhausen pour nous avoir signalé une erreur numérique dans la fin de cet article. 相似文献
89.
Reactions of HgCl2 with η5-C5H5Fe(CO)2R (R CH2CHCH2 and CH2C(CH3)CH2) in THF at 25°C rapidly afford adducts of the two reactants. These adducts were converted to the corresponding PF6? salts, [η5-C5H5Fe(CO)2(η2-CH2C(R)CH2HgCl)]+ PF6? (R H and CH3), for characterization. Slower reactions with cleavage of the ironcarbon σ bond and elimination of the R group from η5-C5H5Fe(CO)2R occur for R CH2CHC(CH3)2, CH2CHCHC6H5, and CH2CCC6H5. Both elimination and adduct formation are observed when R CH2CHCHCH3. The kinetics of the cleavage reactions are presented and possible mechanisms for both cleavage and adduct formation are discussed. 相似文献
90.
We report three highly stereoselective pericyclic reactions occurring in cascade leading to the synthesis of Decalins skeletons possessing two contiguous quaternary centers. The tandem reaction is triggered by an oxy-Cope rearrangement to create in situ a 10-membered ring enol ether macrocyle 6, which immediately rearranges via a Claisen [3,3] shift to the corresponding E-cyclodec-6-en-1-one 7. The latter spontaneously cyclizes via a transannular ene reaction to produce Decalin 5. Analysis of the mechanism with respect to the origin of the high diastereoselectivity of the tandem oxy-Cope/Claisen/ene reaction is presented. 相似文献