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1.
2.
Theoretical studies on the thermolysis in the gas phase of alkyl N,N-dialkylcarbamates were carried out using ab initio theoretical methods, at the MP2/6-31G(d), MP2/6-31++G(d,p) and MP2/6-311++G(2d,p)//MP2/6-31G(d) levels. The reactions have two steps: the first one corresponds to the formation of an alkene and a neutral dialkylcarbamic acid intermediate via a six-membered cyclic transition state; the second one is the decarboxylation of this intermediate via a four-membered cyclic transition state, leading to carbon dioxide and the corresponding dialkylamine. The progress of the reactions was followed by means of the Wiberg bond indices. The results indicate that the transition states have character intermediate between reactants and products, and the calculated synchronicities show that the reactions are slightly asynchronous. The bond-breaking processes are more advanced than the bond-forming ones, indicating a bond deficiency in the transition states. The rate constants calculated for all the reactions agree very well with the available experimental data.From the Proceedings of the 28th Congreso de Químicos Teóricos de Expresión Latina (QUITEL 2002) 相似文献
3.
V. F. Traven’ I. V. Ivanov A. V. Panov O. B. Safronova T. A. Chibisova 《Russian Chemical Bulletin》2008,57(9):1989-1995
Aromatic imines, namely, 5-formyl-6-hydroxy-4-methyl- and 8-formyl-7-hydroxy-4-methylcoumarin derivatives, have been synthesized.
A dependence of their spectral characteristics (1H NMR spectra, electronic absorption spectra) from the solvent (DMSO, CHCl3, DMF, acetonitrile, MeOH) has been studied. The solvatochromic effects observed for a number of imines, first of all, for
7-hydroxy-4-methyl-8-(4′-nitrophenylimino)methyl-2H-1-benzopyran-2-one, were related to their E/Z-isomerization with respect to the C=N bond based on the quantum chemical calculations by the AM1, PM3, PPP CI methods.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1954–1960, September, 2008. 相似文献
4.
Krzysztof Waskiewicz Rafal Gabanski Radoslaw Motyka Mieczyslaw Lapkowski Jerzy Suwinski Jerzy Zak 《Journal of Electroanalytical Chemistry》2008,617(1):27-37
The group of 1,4-dialkoxy-2,5-bis[2-(thien-2-yl)ethenyl]benzene stereoisomers was synthesized in which methoxy- and ethoxy-groups were used as alkoxy-substituents. These isomers were characterized as solution species both electrochemically and spectroscopically. As expected, these compounds, having a stilben like structure, are the subject of photoisomerization, which is described and discussed. It is demonstrated how electrochemical process may cause isomerization of the double CC bonds in that group of compounds. An attempt of using electrochemical methods to monitor the process of photoisomerization of these compounds is presented. Mechanism of the oxidatively induced electrochemical isomerization has been proposed and discussed. The electrochemical isomerization mechanism is verified by digital simulation, which allowed estimating basic kinetic parameters of the processes. 相似文献
5.
The (E)-α-selenylvinylstannanes react with acyl halides in presence of a catalytic amount of Pd(PPh3)4 to give the corresponding (Z)-α-selenyl-α,β-unsaturated ketones in good yield. 相似文献
6.
A. I. Krivoshey N. S. Pivnenko S. V. Shishkina A. V. Turov L. A. Kutulya O. V. Shishkin 《Russian Chemical Bulletin》2006,55(6):999-1009
The spatial structure of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone prepared by photochemical isomerization of the E-isomer was studied by analyzing the magnitudes and temperature dependence of the proton spin-spin coupling constants obtained
by 1H NMR spectroscopy and the results of molecular modeling using semiempirical quantum chemical AM1 and PM3 methods and the
density functional theory (DFT). Comparison of the results obtained for the Z-and E-isomers shows that in both cases the conformational equilibrium for both isomers is characterized by significant preference
of the chair conformer having an equatorial methyl group, namely, − ΔH (chair a ⇌ chair e) = 1.98–2.12 and 1.36–1.54 kcal mole−1 for the Z-and E-isomers, respectively. Distinctions in the non-planarity of the enone fragment and cyclohexanone ring in the Z-and E-isomers under study following from the results of mathematical modeling were confirmed by the experimental values of the
geminal spin-spin coupling constants of protons of the methylene groups in α,α ′-positions with respect to the enone group.
Quantum chemical calculations of the Z-isomer revealed the existence of intramolecular hydrogen bond between the carbonyl oxygen and the nearest aromatic proton
in ortho-position of the benzene ring. Possible reasons for different helical twisting power of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone and the E-and Z-arylidene derivatives of 1R, 4R-isomenthone in the mesophase are discussed based on the results of molecular structure studies for these compounds.
In the text below the unsaturated ketones under study will be called “arylidene cyclohexanone derivatives” for convenience
of comparing the characteristics of methylcyclohexanone and isomenthone derivatives.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 962–972, June, 2006. 相似文献
7.
M.R. Bermejo E. Barrado A.M. Martínez Y. Castrillejo 《Journal of Electroanalytical Chemistry》2008,617(1):85-100
The electrodeposition of lutetium on inert electrodes and the formation of lutetium–aluminium alloys were investigated in the eutectic LiCl–KCl in the temperature range 673–823 K. On a tungsten electrode, the electroreduction of Lu(III) proceeds in a single step and electrocrystalization plays an important role. Experimental current–time transients are in good agreement with theoretical models based on either instantaneous or progressive nucleation with three dimensional growth of the nuclei, depending on the working temperature. The diffusion coefficient of Lu(III) was determined by chronopotentiometry by applying the Sand equation. The activation energy for diffusion was found to be 31.5 ± 1.3 kJ mol−1. Al3Lu and mixtures of Al3Lu and Al2Lu, characterized by XRD analysis and SEM, were obtained from the LiCl–KCl melt containing Lu(III) by potentiostatic electrolysis using an Al electrode. The activity of Lu and the standard Gibbs energies of formation for Al3Lu were estimated from open-circuit chronopotentiometric measurements. The E–pO2−(potential–oxoacidity) diagram for Lu–O stable compounds in LiCl–KCl at 723 K has been constructed by combining theoretical and experimental data. In this way, the apparent standard potential for the Lu(III)/Lu system has been determined by potentiometry. Potentiometric titrations of Lu(III) solutions with oxide donors, using a yttria stabilized zirconia membrane electrode “YSZME” as a pO2− indicator electrode, have shown the stability of LuOCl and Lu2O3 in the melt and their solubility products have been determined at 723 K. 相似文献
8.
M. T. Omar K. A. Kandeel A. S. A. Youssef 《Monatshefte für Chemie / Chemical Monthly》1995,126(4):439-446
Summary 3-Aryl-, 3-benzyl-, and 3H-5-(2-aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidines3a–h react with bromine in acetic acid solution to give mixtures of the respective 5-aroylmethylene (E) and (Z) diastereomeric derivatives5 and6. They contain more than 85% of the (E)-diastereomers along with some pure isomers. The intermediacy of the 5-bromo derivatives4 is proven and a plausible route of the reaction is presented. Structures of compounds3–6 are evidenced by analytical and spectral data.
Das Verhältnis von (E)- und (Z)-Isomeren bei der Reaktion von 5-(2-Aryl-2-oxomethyl)-2-thioxo-4-oxo-1,3-thiazolidinen mit Brom
Zusammenfassung 3-Aryl-, 3-Benzyl- und 3H-5-(2-Aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidine3a–h reagieren mit Brom in essigsaurer Lösung zu Gemischen der entsprechenden diastereomeren 5-Arylmethylen-Derivate ((E) und (Z))5 und6. Sie enthalten mehr als 85% des (E)-Diastereomeren. Die intermediäre Natur der 5-Brom-Derivate4 wird bewiesen; ein Reaktionsweg wird vorgeschlagen. Die Strukturen der Verbindungen3–6 werden durch analytische und spektroskopische Daten abgesichert.相似文献
9.
Pivnenko N. S. Vashchenko V. V. Kutulya L. A. Doroshenko A. O. Chepeleva L. V. 《Russian Chemical Bulletin》2001,50(9):1596-1604
The 1Í NMR method in combination with molecular simulation was used to study conformations of Z- and E-isomers of (1R,4R)-cis-2-(4-methoxyphenyl)benzylidene-p-menthan-3-one. In solutions the Z-isomer, unlike the conformationally uniform Å-isomer, is an equilibrium mixture of chair conformers with the substantial predomination of one form with the axially oriented methyl and equatorial isopropyl groups (75—78%). The enone group is more nonplanar in the Z-isomer than in the Å-isomer. For the isopropyl fragment, the equiprobable existence of trans- and two gauche-rotamers for the Z-isomer and a substantial predomination of gauche-forms in the case of the E-isomer were established. 相似文献
10.
Mohamed Abdou Christoph Kratky Georg Uray 《Monatshefte für Chemie / Chemical Monthly》1990,121(12):1039-1043
Summary The crystal structure of (–)-diphenylethanediammonium-(R,R)-tartrate was determined. From this structure determination, the (S,S) configuration was assigned to the (–)-diphenylethanediamine. The asymmetric unit of the crystal structure contains two units of the title compound plus one molecule of ethanol and one water molecule, which form an intricate network of 19 hydrogen bonds.
Die Kristallstruktur von (S,S)-Diphenylethandiammonium-(R,R)-tartrat
Zusammenfassung Es wurde die Kristallstruktur von (–)-Diphenylethandiammonium-(R,R)-tartrat bestimmt. Aus dieser Strukturbestimmung ergab sich die Zuordnung der (S,S)-Konfiguration zum (–)-Diphenylethandiamin. Die asymmetrische Einheit der Kristallstruktur besteht aus zwei Formeleinheiten der Titelverbindung sowie einem Molekül Ethanol und einem Wassermolekül, welche ein komplexes Netzwerk von insgesamt 19 Wasserstoffbrücken bilden.相似文献
11.
Bożena Modzelewska-Banachiewicz Barbara Michalec Teresa Kamińska Liliana Mazur Anna E. Kozioł Jacek Banachiewicz Marzena Ucherek Martyna Kandefer-Szerszeń 《Monatshefte für Chemie / Chemical Monthly》2009,140(4):439-444
Abstract (Z)-3-(3,4-diaryl-1,2,4-triazole-5-yl)prop-2-enoic acid derivatives were obtained in the course of the reaction of N
3-substituted amidrazones with maleic anhydride, and isomerized into the (E) isomers by heating under reflux in acetic acid solution. The molecular structure of the compounds obtained was confirmed
by IR and 1H NMR spectroscopy, and by X-ray crystallography for (2E)-3-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)prop-2-enoic acid. The antiviral and immunomodulating activity of several of the compounds was examined.
Graphical abstract
相似文献
12.
D. Kh. Zheglova D. G. Genov A. V. Gribanov A. I. Kol'tsov S. N. Smirnov 《Monatshefte für Chemie / Chemical Monthly》1994,125(12):1443-1446
Summary
1H,13C, and CP/MAS13C NMR spectra of sixp-substituted 1-aryl-3-arylamino-2-propen-1-ones in solution and in the solid state are reported and discussed. In the proteon-accepting solvent dimethylsulfoxide, electronegative substituents shift the isomeric equilibrium to the (E)-isomer. Bulky substituents promote crystallization of the (Z)-form.
NMR-Spektroskopische Untersuchung der (Z)/(E)-Isomerie von 1-Aryl-3-arylamino-2-propen-1-onen in Lösung und im Kristallzustand (Kurze Mitt.)
Zusammenfassung 1H-,13C- und CP/MAS-13C-NMR Spektren von sechsp-substituierten 1-Aryl-3-arylamino-2-propen-1-onen in gelöstem und festem Zustand werden berichtet und diskutiert. In protonenakzeptierendem Dimethylsulfoxid verschieben elektronegative Substituenten das Gleichgewicht zum (E)-Isomer. Große Substituenten begünstigen die Kristallisation in der (Z)-Form.相似文献
13.
1-O-α-
-Glucopyranosyl-
-mannitol–ethanol (2/1), (C12H24O11)2–C2H5OH, crystallizes in the monoclinic space group P21 with unit cell dimensions a=11.4230(8) Å, b=9.525(4) Å, c=15.854(2) Å, β=102.751(7)° and V=1682.4(7) Å3, Z=2, Dx=1.45 Mg m−3, λ (Mo-Kα)=0.71069 Å, μ=0.128 mm−1, F(000)=788 and T=293(2) K. The structure was solved by direct methods and refined by least-squares calculations on F2 to R1=0.0371[I>2σ(I)], and 0.0930 (all data, 3542 independent reflections, Rint=0.021). There are two molecules of glucopyranosylmannitol (GPM) and one ethanol molecule in the asymmetric unit, and the glucopyranosyl ring adopts a chair conformation in both GPM molecules. Bond lengths and angles accord well with the mean values of related structures. The conformation along the mannitol side chain for one of the GPM molecules was the same as for the known polymorphs of
-mannitol, while the conformation of the other molecule was different, indicating different conformational arrangements in the terminal carbon atoms of the mannitol side chains of the two GPM molecules. The structure in 1-O-α-
-glucopyranosyl-
-mannitol–ethanol (2/1) is held together by a very complex hydrogen bonding system, which consists of an infinte chain propagating along the b-axis and a discontinuous chain, which binds the ethanol molecule to the structure. The FTIR spectra for anhydrous GPM, GPM dihydrate and GPM–ethanol (2/1) were recorded. Both IR and X-ray results indicate the extensive hydrogen bonding in crystalline state. 相似文献
14.
A series of condensation products of 1-(9-butylcarbazol-3-yl)-5-oxopyrrolidine-3-carbohydrazide with 2-propanone, 2-butanone,
2,4-pentanedione, 2,5-hexanedione, ethyl 3-oxobutanoate, and aromatic aldehydes was obtained. Substituted oxadiazoles were
synthesized from carbohydrazide or the corresponding hydrazone. Spectral properties of the synthesized compounds were examined.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1009–1017, July, 2008. 相似文献
15.
L. C. Porter Ming-Li F. Cervantes-Lee H. H. Murray III 《Monatshefte für Chemie / Chemical Monthly》1993,124(6-7):775-782
Summary Semiempirical (PM3 type) calculations have been carried out on theE isomer of acetophenone phenylhydrazone and extended to include acetophenoneimine and phenylhydrazone. The optimized structure of acetophenone phenylhydrazone has also been compared with the solid state structure obtained from the results of an X-ray crystal structure determination. The crystals are monoclinic, space group P21/c,a=5.520(2) Å,b=8.944(3) Å,c=23.591(8) Å, =90.28(3)°, andV=1164.7(7) Å3. The finalR value is 0.0549 for 1097 reflections withF>3(F). The structure possesses a planar conformation and both N atoms possess trigonal-planar geometries. Results of the theoretical calculation are in good agreement with those obtained from the crystallographic data and indicate that conjugation between the hydrazone region and the phenyl rings plays a significant role in favoring a planar molecular conformation and has a significant perturbing influence on the bond lengths and angles associated with the hydrazone C=N-N atoms. A Mulliken analysis for the structure gives bond orders of 1.77 and 1.10 for the formally double bonded C-N and single-bonded N-N atoms, respectively.
Bindungen in Phenylhydrazonen. Röntgenstrukturanalyse und theoretische Berechnungen an (E)-Acetoxyphenon-phenylhydrazin
Zusammenfassung Es wurden semiempirische PM3-Typ-Berechnungen für dasE-Isomere von Acetophenon-phenylhydrazon durchgeführt und dann auf Acetophenonimin und Phenylhydrazon ausgeweitet. Die optimierte Geometrie von Acetophenon-phenylhydrazon wurde mit der Kristallstruktur dieser Verbindung verglichen. Die Kristalle sind monoklin, Raumgruppe P21/c,a=5.520(2) Å,b=8.944(3) Å,c=23.591(8) Å, =90.28(3)° undV=1164.7(7) Å3. Der endgültigeR-Wert für 1097 Reflexe mitF>3(F) war 0.0549. Die Struktur besitzt eine planare Konformation und beide N-Atome haben trigonal-planare Geometrien. Die Ergebnisse der theoretische Berechnungen sind in guter Übereinstimmung mit jenen aus den kristallographischen Daten und zeigen, daß die Konjugation zwischen dem Hydrazonteil und den Phenylringen eine signifikante Rolle bei der planaren Konformation trägt und auch einen entscheidenden Einfluß auf Störungen bei Bindungslängen und-winkel in der Hydrazongruppierung C=N-N hat. Eine Mulliken-Analyse der Struktur ergab Bindungsordnungen von 1.77 bzw. 1.10 für die formale Doppelbindung C-N bzw. die Einfachbindung N-N.相似文献
16.
A simple, five-step synthesis of the title compound was developed starting from commercially available 2,4-nonadienal. The overall yield of the pheromone is 29%, and the geometric purity of the 4 and 7 double bonds is 95%. TheZ configuration of the 7 bond results from the 1,4-cis-hydrogenation of the intermediate 1,4,6-undecatrien-3-ol in the presence of an (arene)chromium tricarbonyl complex, while theE configuration of the 4 bond arises in the Claisen-Johnson rearrangement occuring in the reaction of 1,5Z-undecadien-3-ol with trimethyl orthoacetate.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2350–2353, September, 1996. 相似文献
17.
Yu. N. Belokoń Yu. N. Bubnov T. D. Churkina A. A. Chesnokov K. A. Kochetkov N. Yu. Kuznetsov V. N. Khrustalev N. I. Raevskii 《Russian Chemical Bulletin》1997,46(5):982-989
The stereochemistry of addition of Br2 toE-andZ-(R)-N-cinnamoyl-4-phenyloxazolidin-2-ones was studied. It was established that both theE-andZ-isomers give only two out of four possible diastereoisomers in the presence of Lewis acids (BPr3 or AlBr3). The absolute configurations of the diastereoisomers [(2S', 3R') and (2R', 3S') of the side chain] were established by X-ray structural analysis. The stereochemistry observed is a consequence of the stepwise
bromination and the absence of bridging bromine atoms along the reaction coordinate. In the case of theZ-isomer, the diastereoselectivity of the reaction was high, whereas it is low in the case of theE-isomer. It was suggested that at the first stage of addition of Br2 at the C=C bond, the attack of the Br+ cation occurs at the α position, and the second stage of transfer of Br− occurs with the participation of boron or aluminum complexes in the intermediate state of the bromination reaction. This
hypothesis as well as the results of calculations of the initial conformations of the substrates provide an explanation of
the regularities observed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1022–1028, May, 1997. 相似文献
18.
O. Ya. Borbulevych O. V. Shishkin I. R. Gol'ding V. N. Khrustalev Yu. G. Gololobov 《Russian Chemical Bulletin》1998,47(10):1935-1939
X-ray study of 2-cyano-(2E)-pentadien-2,4-oic acid (1) and its ethyl ester (2) showed that the molecules of1 and2 in the crystalline phase form stacks by translating along the shortest crystallographic axis. The nature of the intermolecular
interactions favoring the formation of such β-structures was analyzed within the framework of the Bader topological theory.
Possible routes of topochemical reactions of compounds1 and2 are considered.
Dedicated to the memory of Academician M. I. Kabachnik on his 90th birthday.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1991–1995, October, 1998. 相似文献
19.
Yu. Yu. Morzherin M. F. Kosterina V. S. Berseneva W. Dehaen V. A. Bakulev 《Russian Chemical Bulletin》2002,51(7):1292-1297
The equilibrium concentrations of E- and Z-isomers of thiazolidin-4-ones containing exocyclic double bonds in positions 2 and 5 of the cycle were determined in DMSO-d6. The influence of the nature of the substituents on the equilibrium position was found. Electron-releasing substituents stabilize the E,Z-configuration and electron-withdrawing substituents stabilize the Z,Z-configuration. The association constants of E- and Z-2-ethoxycarbonylmethylenethiazolidin-4-ones with the sodium cation were determined by 1H NMR spectroscopy. 相似文献
20.
原子簇化合物[WS4Cu3Br(bipy)2]的晶体结构和非线性光学性质 总被引:1,自引:0,他引:1
The title cluster compound [WS4Cu3Br(bipy)2] has been synthesized by the reaction of (NH4)2[WS4], CuBr and 2,2′-bipy in DMF solution. Single crystal X-ray diffraction data show that the compound has a nest-shaped structure. Nonlinear optical properties (NLO) of the cluster were investigated by a Z-scan technique with a pulsed laser at 532nm. The cluster exhibits the strong NLO absorption and a self-defocusing effect (effective non-linear absorption coefficient, α2eff=7.3×10-11mW-1; effective non-linear refractive index, n2eff=3.9×10-11esu) when measured in a 6.0×10-4mol·dm-3 DMF solution. CCDC: 200397. 相似文献