共查询到20条相似文献,搜索用时 250 毫秒
1.
Valentine P. Ananikov 《Central European Journal of Chemistry》2004,2(1):196-213
A convenient methodology was developed for a very accurate calculation of 13C NMR chemical shifts of the title compounds. GIAO calculations with density functional methods (B3LYP, B3PW91, PBE1PBE) and
6-311+G(2d,p) basis set predict experimental chemical shifts of 3-ethynylcyclopropene (1), 1-ethynylcyclopropane (2) and 1,1-diethynylcyclopropane (3) with high accuracy of 1–2 ppm. The present article describes in detail the effect of geometry choice, density functional
method, basis set and effect of solvent on the accuracy of GIAO calculations of 13C NMR chemical shifts. In addition, the particular dependencies of 13C chemical shifts on the geometry of cyclopropane ring were investigated. 相似文献
2.
V. A. Maksakov V. P. Kirin S. V. Tkachev A. V. Golovin 《Russian Chemical Bulletin》1999,48(11):2158-2161
The migration of the double bond in the allylcarboxamide ligands of (μ-H)Os3(μ-O=CN RCH2CH=CH2) (CO)10 (R=H (1) or CH3 (2)), (μ-D)Os3(μ-O=CNDCH2CH=CH2) (CO)10, and (μ-H)Os3(μ-O=CNHCD2CH=CH2)(CO)10 clusters was studied by1H,2H, and13C NMR spectroscopy. Neither μ-D nor ND groups in the deuterated complexes are directly involved in prototropic processes of
allylic rearrangement. Initially, the deuterium atom of the CD2 group migrates to the ψ-carbon atom of the allyl fragment to form the −CD=CH-CH2D propenyl moiety, in which the deuterium and hydrogen atoms are gradually redistributed between the ψ-and β-carbon atoms.
The triosmium cluster complexes containing the bridging carboxamide ligands O=CNRR' catalyze the allylic rearrangement ofN-allylacetamide. Based on the data obtained, the probable scheme of the allylic rearrangements in clusters1 and2 was proposed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2182–2186, November, 1999. 相似文献
3.
L. O. Nindakova N. N. Chipanina V. K. Turchaninov M. V. Ustinov B. A. Shainyan 《Russian Chemical Bulletin》2005,54(10):2343-2347
The reaction of di-μ-chlorobis(1,5-cyclooctadiene)dirhodium with (4S, 5S)-2,2-dimethyl-4,5-bis(methylaminomethyl)-1,3-dioxolane (1) gave the complex [Rh(cod)(1)]Cl (cod is 1,5-cyclooctadiene). The composition of the complexes CoCl2 · L2 and [Rh(cod)(L2)]X (L2 = 1, (4S,5S)-2,2-dimethyl-4,5-bis(aminomethyl)-1,3-dioxolane, and (4S, 5S)-2,2-dimethyl-4,5-bis(dimethylaminomethyl)-1,3-dioxolane; X = Cl, TfO) was studied using IR and 1H NMR spectroscopy. In the RhI cyclooctadienediamine complexes, the diene molecule forms a stronger bond with the metal atom than that in the cyclooctadienediphosphine
analogs.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2270–2274, October, 2005. 相似文献
4.
Reactions of 2-(4,5-dihydro-3-furyl)-1,3-diphenyl-1,3-diaza-2λ3-phospholidine (1) with nitrile imines are multistep processes involving cleavage of one P-N bond of the diazaphospholidine ring to form substituted
5-(2-chloroethyl)-4-(N,N′-diphenylethylenediamino)-1,4-dihydro-1,2,4λ5-diazaphosphorines 4 as final products. Analogs of phospholidine 1, namely, 4,5-dihydro-3-furylphosphonous dipiperidide and dimorpholide, react with C,N-diphenylnitrile imine with retention of both P-N bonds to give 5-(2-hydroxyethyl)-1,2,4-diazaphosphorinium chlorides.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1590–1593, July, 2005. 相似文献
5.
A. A. Kamyshova A. Z. Kreindlin P. V. Petrovskii A. S. Peregudov Yu. A. Borisov A. A. Koridze 《Russian Chemical Bulletin》2005,54(12):2805-2812
The reaction of [Cp*2RuBr]+Br− with bromine in CH2Cl2 (CD2Cl2) in an inert atmosphere at room temperature produces the complexes [Cp*Ru(Br)C5Me4CH2Br]+Br3
− (syn conformer), [Cp*Ru(Br)C5Me3(CH2Br)2]+ (syn and anti conformers), and [Ru(Br)(C5Me4CH2Br)2]+ (syn conformer). All complexes were characterized by 1H and 13C NMR spectroscopy; the former complex, by elemental analysis. These complexes were also prepared by the reaction of [Cp*RuC5Me4CH2]+BF4
− with bromine in CH2Cl2.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2712–2718, December, 2005. 相似文献
6.
N. G. Akhmedov E. A. Katsman S. G. Malyugina V. I. Mstislavsky Yu. F. Oprunenko V. A. Roznyatovsky Yu. A. Ustynyuk A. S. Batsanov N. A. Ustynyuk 《Russian Chemical Bulletin》1997,46(10):1769-1786
The reaction of phenalene with Cr(CO)3Py3/BF3·OEt2 afforded a mixture of two isomeric complexes, tricarbonyl(6a,7-9,9a,9b-·6-phenalene)chromium (1) and tricarbonyl(3a,6a,9b,4-6-·6-phenalene)chromium (2). Deprotonation of the mixture of compounds1 and2 followed by treatment with MeI, BunI, or D2O gave complexesexo-1-R-1 (3–5: R=Me (3), Bun (4), or D (5)). The molecular geometry of complex3 was established by X-ray structural analysis. Heating of complex5 in toluene or C6F6 at 90–110 °C resulted in redistribution of deuterium among positionsexo-1,endo-1, and 3 in the resulting complexes of types1 and2
via sigmatropic shifts of the H
exo
and H
endo
atoms in the nonaromatic ring as well asvia inter-ring migrations of the tricarbonylchromium group. In the case of3, the methyl label is distributed among positionsexo-1 and3 to form isomeric complexes with similar structures (exo-1-Me-2 (6), 3-Me-2 (7), and 3-Me-1 (8), respectively)via processes analogous to those observed in the case of isomerization of compound5 (except for migration of the H
exo
atom). The mechanisms of these rearrangements are discussed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1863–1880, October, 1997. 相似文献
7.
Lenoble V Garnier C Masion A Ziarelli F Garnier JM 《Analytical and bioanalytical chemistry》2008,390(2):749-757
This work allowed the characterization of the Cd-binding sites of two compounds taken as models for exudates, the main components
of soil organic matter (SOM). The studied compounds were exopolysaccharides (EPS), specifically exudates of roots (polygalacturonic
acid) and of soil bacteria (Phytagel). Potentiometric acid–base titrations were performed and fitting of the obtained results
indicated the presence of two main classes of acidic sites, defined by their pK
a values, for both EPS but of a different nature when comparing the two compounds. The two studied exopolysaccharides presented
different acidic/basic site ratios: 0.15 for Phytagel and 0.76 for polygalacturonic acid. Spectroscopic techniques (13C/113Cd NMR, FTIR) distinguished different Cd surroundings for each of the studied EPS, which is in agreement with the titration
results. Furthermore, these analyses indicated the presence of –COOH and –OH groups in various proportions for each exopolysaccharide,
which should be linked to their reactivity towards cadmium. Cadmium titrations (voltammetric measurements) also differentiated
different binding sites for each compound and allowed the determination of the strength of the Cd-binding site of the EPS.
Fitting of the results of such voltammetric measurements was performed using PROSECE (Programme d’Optimisation et de Speciation Chimique dans l’Environnement), a software coupling chemical speciation calculation and binding parameter optimization. The fitting, taking into account
the Cd2+/H+ competition towards exopolysaccharides, confirmed the acid-base titrations and spectroscopic analyses by revealing two classes
of binding sites: (i) one defined as a strong complexant regarding its Cd2+–EPS association (logK = 9–10.4) and with basic functionality regarding H+–EPS association (pK
a = 11.3–11.7), and (ii) one defined as a weak complexant (logK = 7.1–8.2) and with acidic functionality (pK
a = 3.7–4.0). Therefore the combination of spectroscopic analyses, voltammetry, and fitting allowed the precise characterization
of the binding sites of the studied exopolysaccharides, mimicking the main SOM components. Furthermore, the binding parameters
obtained by fitting can be used in biogeochemical models to better define the role of key SOM compounds like exudates of roots
and of soil bacteria on trace metal transport or assimilation. 相似文献
8.
The effects of La3+ on inward K+ channels at plasma membrane in vicia guard cells are investigated using the whole-cell patch-clamp recording mode. It is
shown that La3+ on both sides of plasma membrane blocks inward K+ currents in a concentration-dependent manner, indicating that La3+ binding sites may exist on both sides of plasma membrane in guard cells in vicia. The dose response is fitted by the Michaelis-Menten
relation characterized by an inhibitor constant K
i
of 2.56±0.25 μmol · L−1 (outside membrane) and (1.18±0.11)×10−15 mol · L−1 (inside membrane). Intracellular La3+ has much stronger inhibitory effect on inward K+ currents than extracellular La3+ does, suggesting there may exist stronger binding sites inside membrane than outside membrane. Since ion channel activities
of guard cells directly affect plant stomatal movement and water status, our results imply that rare earth elements might
have potential practical values in regulating plant water status and strengthening plant drought endurance. 相似文献
9.
I. M. Chung H. Y. Park S. C. Chun J. J. Kim A. Ahmad 《Chemistry of Natural Compounds》2007,43(4):417-421
Three new compounds, 4-hydroxymethylene-7-(9,9,13-trimethylcyclohexyl)-heptanyl-3′,7′,7′-trimethylcyclohexa-2′,4′-dien-1′-oate
(1), 1-(n-hexadec-7-enoxy)-6-(n-octadecanoxy)-β-D-glucopyranoside (2), and (Z)-12-hydroxy-9-octadecenoic acid-12-β-D-glucopyranoside (3), along with the known compound hexacosanoic acid (4), were isolated and identified from the rice hulls of Oryza sativa. Their structures were elucidated by 1D and 2D NMR spectroscopic techniques (1H-1H COSY, 1H-13C HETCOR, DEPT) aided by EIMS, FABMS, HRFABMS, and IR spectra.
Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 344–347, July–August, 2007. 相似文献
10.
D. A. Loginov A. A. Pronin L. S. Shul’pina E. V. Mutseneck Z. A. Starikova P. V. Petrovskii A. R. Kudinov 《Russian Chemical Bulletin》2008,57(3):546-551
The mononuclear arene complexes [Cb*Co(arene)]+ (3a–g; Cb* = C4Me4; arene is biphenyl (a), diphenylmethane (b), 1,2-diphenylethane (c), diphenyl ether (d), p-terphenyl (e), 1,2-dimesitylethane (f), or 1,3-dimesitylpropane (g)) were synthesized by the reactions of arenes either with the benzene complex [Cb*Co(C6H6)]+ (1) under visible light irradiation or with the acetonitrile derivative [Cb*Co(MeCN)3]+ (2) in refluxing THF. The reactions of 2 with 1,2-diphenyle-thane, 1,3-dimesitylpropane, and p-terphenyl in a ratio of 2: 1 afforded the dinuclear complexes [Cb*Co(μ-η:η-arene)CoCb*]2+ (4c,e,g). The stability of the dinuclear arene complexes was estimated by DFT calculations. The structures of the complexes [3a]PF6 and [3e]PF6 ere established by X-ray diffraction.
For Part 6, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 535–539, March, 2008. 相似文献
11.
N. N. Il'chenko V. N. Britsun M. O. Lozinskii 《Theoretical and Experimental Chemistry》2005,41(5):284-289
The keto-enol-enethiol tautomerism in 3-oxo-3-R1-N-R2-propanethioamides under vacuum and in acetone was studied in terms of density functional theory. It was established that
the equilibrium depends on the structure of the 3-oxo-3-R1-N-R2-propanethioamides and on the nature of the solvent, but the most stable form is as a rule the keto form stabilized by an
intramolecular hydrogen bond.
__________
Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 272–277, September–October, 2005. 相似文献
12.
Imine-bridged TTF-π-pyridine derivatives, 2NTTF, 3NTTF and 4NTTF, were synthesized and the cation-binding study was performed.
It is noted that with the addition of the micromolar concentration of Pb2+ to the solution, these compounds display remarkable changes in solution color, 1H NMR spectra and electrochemical properties. The nitrogen atom of the imine-bridge in 2NTTF not only serves as a π-conjugated
spacer but also participates in the sensing and coordinating properties.
Supported by the National Natural Science Foundation of China (Grant Nos. 20732007, 20728506 & 20672122), the Ministry of
Science and Technology of China (Grant Nos. 2006CB806105, 2007CB808004, 2007CB936001 & 2009CB-22008) and the Bureau for Basic
Research of the Chinese Academy of Sciences 相似文献
13.
The formation and fragmentation energies of the proton and sodium cation complexes with monosubstituted methane, cyclohexane,
and benzene derivatives in which carbon atoms are bonded to substituents (NH2, OH, F, Cl, Br, ONO2, NO2, COOH, CN, and Ph) were calculated by the B3LYP/6-31G(d) method. For [M + Na]+ complexes, the formation energies are much lower (and differ from one another to a much lesser extent), while the dissociation
energies are much higher, than the corresponding energies of the [M + H]+ complexes. Na+ cation shows a lower selectivity toward localization at functional groups in molecules compared to H+.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 246–249, February, 2008. 相似文献
14.
Jian Zhang Zhi-Qi Yin Peng Cao You-Bin Li Jin-Ao Duan 《Chemistry of Natural Compounds》2008,44(6):701-703
A new flavonol derivative 3, 8-dihydroxy-10-methoxy-5-H-isochromeno[4, 3-b]chromen-7-one (1) together with four known compounds, glutinone (2), luteolin (3), acacetin 7-O-α-L-rhamnopyranosyl- (1→6)-β-D-glucopyranoside (4), and rutin (5) were isolated from the dried roots of Fagopyrum dibotrys. Their structures were determined by UV, IR, MS, 1H, and 13C NMR spectroscopic analysis, including 2D NMR.
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 567–568, November–December, 2008. 相似文献
15.
The photoluminescence properties of xZnO–(100−x)SiO2 (x = 0, 5, 10, 20) containing 1% Eu2O3 prepared by a sol–gel method were systematically investigated. The results indicated that the relative proportion of f–f transitions to charge transfer (CT) absorption decreased with the increase of ZnO concentration. The intensity of 5D0–7FJ transitions of Eu3+ ions was enhanced with the increase of ZnO content due to local structure changes and decreased quantities of Eu3+ ions clusters. The results of fluorescence line narrow (FLN) spectra indicated that Eu3+ ions occupied one site in SiO2 glass and two sites in ZnO–SiO2 glasses. The second-order crystal field parameters were calculated. B20 and B22 for site 1 increased with excitation energy, while ones hardly changed for site 2. 相似文献
16.
A coupling equation relating the quadrupole coupling constant (e2
Qq
zz
) to the asymmetry parameter (η) of the electric field gradient for a series of cobaltocenium derivatives (59Co NQR) is derived. The estimates of the correlation times of “slow” modulations of electron motions by tunneling processes
lie in the range from 10−12 to 10−14 s. This corresponds to the interval of the characteristic times of nuclear motions.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1919–1923, October, 2007. 相似文献
17.
A. S. Volk I. N. Krasikova S. D. Anastyuk P. S. Dmitrenok T. F. Solov’eva 《Chemistry of Natural Compounds》2007,43(5):519-524
The structure of lipid A from the marine γ-proteobacterium Pseudoalteromonas nigrifaciens IAM 13010T that was prepared by hydrolysis of the corresponding lipopolysaccharide by acetic acid (1%) was determined by chemical analysis,
13C NMR spectroscopy, and MALDI/TOF and LSIMS mass spectrometry. It was shown that lipid A is a β-1,6-bonded disaccharide of glucosamine that is substituted by two phosphoric acids (in the C1 and C4′ positions), two (R)-3-hydroxyalkanoic
(normal and branched) acids with ester bonding (at the C3 and C3′-positions), and (R)-3-hydroxydodecanoic and (R)-3-dodecanoyloxydodecanoic
acids (both with amide bonding at C2′ and C2, respectively). It was hypothesized that this type of structure is typical of
lipid A from bacteria of the genus Pseudoalteromonas in general.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 425–429, September–October, 2007. 相似文献
18.
Ribeiro Guevara S Zizek S Repinc U Pérez Catán S Jaćimović R Horvat M 《Analytical and bioanalytical chemistry》2007,387(6):2185-2197
Mercury tracers are powerful tools that can be used to study mercury transformations in environmental systems, particularly
mercury methylation, demethylation and reduction in sediments and water. However, mercury transformation studies using tracers
can be subject to error, especially when used to assess methylation potential. The organic mercury extracted can be as low
as 0.01% of the endogenous labeled mercury, and artefacts and contamination present during methylmercury (MeHg) extraction
processes can cause interference. Solvent extraction methods based on the use of either KBr/H2SO4 or HCl were evaluated in freshwater sediments using 197Hg radiotracer. Values obtained for the 197Hg tracer in the organic phase were up to 25-fold higher when HCl was used, which is due to the coextraction of 197Hg2+ into the organic phase during MeHg extraction. Evaluations of the production of MeHg gave similar results with both MeHg
extraction procedures, but due to the higher Hg2+ contamination of the controls, the uncertainty in the determination was higher when HCl was used. The Hg2+ contamination of controls in the HCl extraction method showed a nonlinear correlation with the humic acid content of sediment
pore water. Therefore, use of the KBr/H2SO4 method is recommended, since it is free from these interferences. 197Hg radiotracer (T
1/2 = 2.673 d) has a production rate that is about 50 times higher than that of 203Hg (T
1/2 = 46.595 d), the most frequently used mercury radiotracer. Hence it is possible to obtain a similar level of performance
to 203Hg when it is used it in short-term experiments and produced by the irradiation of 196Hg with thermal neutrons, using mercury targets with the natural isotopic composition. However, if the 0.15% natural abundance
of the 196Hg isotope is increased, the specific activity of the 197Hg tracer can be significantly improved. In the present work, 197Hg tracer was produced from mercury 51.58% enriched in the 196Hg isotope, and a 340-fold increase in specific activity with respect to natural mercury targets was obtained. When this high
specific activity tracer is employed, mercury methylation and reduction experiments with minimum mercury additions are feasible.
Tracer recovery in methylation experiments (associated with Me197Hg production from 197Hg2+ spike, but also with Hg2+ contamination and Me197Hg artefacts) with marine sediments was about 0.005% g−1 WS (WS: wet sediment) after 20 h incubation with mercury additions of 0.05 ng g−1 WS, which is far below natural mercury levels. In this case, the amount of Hg2+ reduced to Hg0 (expressed as the percent 197Hg0 recovered with respect to the 197Hg2+ added) varied from 0.13 to 1.6% g−1 WS. Me197Hg production from 197Hg2+ spike after 20 h of incubation of freshwater sediment ranged from 0.02 to 0.13% g−1 WS with mercury additions of 2.5 ng g−1 WS, which is also far below natural levels. 197Hg0 recoveries were low, 0.0058 ± 0.0013% g−1 WS, but showed good reproducibility in five replicates. Me197Hg production from 197Hg2+ spiked in freshwater samples ranged from 0.1 to 0.3% over a period of three days with mercury additions of 10 ng L−1. A detection limit of 0.05% for Me197Hg production from 197Hg2+ spike was obtained in seawater in a 25 h incubation experiment with mercury additions of 12 ng L−1. 相似文献
19.
The structure of galactomannans isolated from seeds of G. delavayi and G. aquatica was studied by 1H and 13C NMR spectroscopy. It was found that the galactomannans consisted mainly of β-1-4-bound mannopyranoses, a part of which was substituted on the C-6 hydroxyl by terminal units of α-galactopyranose.__________Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 12–13, January–February, 2005. 相似文献
20.
S. G. Klepikova V. K. Yu E. E. Fomicheva R. D. Mukhasheva K. D. Praliev K. D. Berlin 《Chemistry of Heterocyclic Compounds》2008,44(11):1398-1403
1H NMR spectroscopy was used to establish that 7-alkoxyalkyl-3-thia-7-azabicyclo[3.3.1]nonan-9-ones and their decarbonylated
derivatives in deuterochloroform solution exist in the double chair conformation. The predominantly formed secondary alcohols
isomers have preferred double chair conformation with the hydroxyl group equatorial relative to the plane of the piperidine
ring. On the other hand, the epimeric alcohols have predominant boat-chair conformation; the piperidine ring takes the boat
form due to intramolecular hydrogen bonding between the unshared electron pair of the nitrogen atom and hydroxyl group proton.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1716–1725, November, 2008. 相似文献