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1.
The equilibrium geometries, excitation energies, force constants and vibrational frequencies for seven low-lying electronic states X 1A 1, 1B 1, 3B 1, 1A 2, 3A 2, 1B 2 and 3B 2 of dichlorocarbene CCl 2 have been calculated at the MRSDCI level with a double-zeta plus polarization basis set. Our calculated equilibrium geometry for the X 1A 1 state, excitation energy for X 1A 1 → 1B 1 and vibrational frequencies for the X 1A 1 and 1B 1 states are in good agreement with experimental data. The electronic transition dipole moments, oscillator strengths for the 1B 1 → X 1A 1 and 1B 2 → X 1A 1 transitions, radiative lifetimes for the 1B 1 and 1B 1 states are calculated using MRSDCI wavefunctions, predicting results in reasonable agreement with experiment. 相似文献
2.
采用CCSD(T)/6-311++G(3 df, 2 pd)//B3LYP/6-311+G(2 df, 2 p)双水平计算方法构建了HO 2+HS反应体系的单、三重态反应势能面,并对该反应主通道的速率常数进行了研究。研究结果表明,标题反应经历了八条反应通道,其中三重态反应通道R1是标题反应主通道。此通道包含路径Path 1 (R → 3IM1 → 3TS1 → P1( 3O 2+H 2S))和Path 1a (R → 3IM1a → 3TS1a → P1( 3O 2+H 2S))两条路径。利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT),分别计算了主路径Path 1和Path 1a在200-800 K温度范围内的速率常数 kTST、 kCVT和 kCVT/SCT,在此温度区间内路径Path 1和Path 1a具有负温度系数效应。速率常数计算结果显示,对主路径Path 1和Path 1a而言,变分效应在计算温度段内有一定影响,与此同时量子力学隧道效应在低温段有显著影响。路径Path 1和Path 1a的CVT/SCT速率常数的三参数表达式分别为 k1CVT/SCT(200-800 K) = 1.54×10 -5T-2.70exp(1154/ T) cm 3 ·molecule -1·s -1和 k1aCVT/SCT(200-800 K) = 5.82×10 -8T-1.84exp(1388/ T) cm 3·molecule -1·s -1。 相似文献
3.
The copolymerization of styrene with methyl methacrylate (S/MMA = 4/1) or acrylonitrile (S/AN = 1/1) in the presence of ethylaluminum sesquichloride (EASC) yields 1/1 copolymer in toluene or chlorobenzene. In chloroform the S-MMA-EASC polymerization yields 60/40 copolymer while the S-AN-EASC polymerization yields 1/1 copolymer. In the presence of EASC, styrene-α-chloroacrylonitrile yields 1/1 copolymer (DMF or DMSO), S-AN yields 1/1 copolymer (DMSO) or radical copolymer (DMF), S-MMA yields radical copolymer (DMF or DMSO), α-methylstyrene-AN yields radical copolymer (DMSO) or traces of copolymer (DMF), and α-MS-methacrylo-nitrile yields traces of copolymer (DMSO) or no copolymer (DMF). When zinc chloride is used as complexing agent in DMF or DMSO, none of the monomer pairs undergoes polymerization. However, radical catalyzed polymerization of isoprene-AN-ZnCl 2 in DMF yields 1/1 alternating copolymer. The copolymerization of S/MMA in the presence of EASC yields 1/1 alternating copolymer up to 100°C, while the copolymerization of S/AN deviates from 1/1 alternating copolymer above 50°C. The copolymerization of S/MMA deviates from 1/1 copolymer at MMA/EASC mole ratios above 20 while the copolymerization of S/AN deviates from 1/1 copolymer at MMA/EASC ratios above 50. 相似文献
4.
Based on the lipase-catalysed kinetic resolution of the silyloxyalcohol (1 RS,2 SR)-5 by transesterification with vinyl acetate in the presence of lipase from Pseudomonas cepacia a synthesis of both enantiomers of the β-amino acid cispentacin (1 R,2 S)-1 and (1 S,2 R)-1 using simple functional group interconversions is described. 相似文献
5.
The kinetics of dehydroxylation of kaolinite and halloysite have been tested by the methods of thermal analysis. They are determined by the particle sizes of these minerals and the order of stacking of the layers in their structures. The Arrhenius activation energy E and order of reaction n decrease with the increase in specific surface area of the minerals. An increase in the degree of disorder of the kaolinite lattice diminishes the value of E. It also influences the n value for fractions finer than 1 m.
Zusammenfassung Die Kinetik der Dehydroxylierung von Kaolinit und Halloysit wurde durch Methoden der Thermoanalyse geprüft. Die Bestimmungen erfolgten über die Teilchengrösse dieser Mineralien und die Reihenfolge der AnhÄufung der Schichten in ihrer Struktur. Die AktivierungsenergieE nach Arrhenius und die Reaktionsordnung nehmen mit zunehmender spezifischer OberflÄche der Minerale ab. Die Zunahme des Grades der Unordnung des Kaolinitgitters setzt den Wert vonE herab. Sie beeinflusst auch den Wertn der Fraktionen feiner als 1m.
Résumé On a étudié par les méthodes de l'analyse thermique, la cinétique de déshydroxylation de la kaolinite et de l'halloysite. Les déterminations ont été effectuées à partir de la taille des particules de ces minéraux et de l'ordre d'empilement des couches dans leur structure. L'énergie d'activationE d'après Arrhénius et l'ordre de réaction diminuent avec l'augmentation de la surface spécifique des minéraux. L'augmentation du degré de désordre du réseau de la kaolinite diminue la valeur deE. Elle influence de mÊme la valeurn des fractions inférieures à 1m.
. . E . E. n 1. 相似文献
6.
Two alkyl ( 1b and 1c) and four fluoroalkyl derivatives ( 1d- 1f) of 4-arylbutyric acid ( 1c, 1d and 1e) and 4-arylbutanol ( 1b, 1f and 1g) [aryl = 2',3'-difluoro-4'-(2-( E-4-pentylcyclohexyl)ethyl)-biphenyl-1-yl] were prepared and investigated in the pure form as nematic materials ( 1b and 1c) and as additives to a ferroelectric liquid crystal (FLC) host ( 1d- 1f). A comparison of 1b and 1c with the decyl analogue 1a demonstrates the effect of terminal chain modification on thermal and electro-optical properties. The substitution of the -CH 2O- ( 1b) or -COO- ( 1c) for -CH 2CH 2- in 1a destabilized the N and SmA phases or completely eliminated the smectic behaviour ( 1c). Dielectric analysis revealed that the chain modification increased the negative Δε, reduced elastic constant K 11 and moderately decreased rotational viscosity γ 1. The temperature dependence of the key electro-optical parameters was analysed for ester 2, the methyl analogue of 1c, which exhibits a 45 K wide N phase. All four fluoroalkyl derivatives 1d- 1f showed enantiotropic SmA phases and 1e also exhibited a monotropic SmC phase. Solutions of 1d- 1f in a FLC host (0.2 mmol g -1) increased the tilt angle Θ (up to 45° for 1g), reduced rotational viscosity γ 1 and the risetime τ. The most dramatic changes were observed for 1g, which contains 15 fluorine atoms. 相似文献
7.
The steady-state UVA (350 nm) photolysis of ( E )-β-ionone ( 1 ) in aerated toluene solutions was studied by 1H NMR spectroscopy. The formation of the 1,2,4-trioxane ( 2 ) and 5,8-endoperoxide ( 5 ) derivatives in the ratio of 4:1 was observed. Time-resolved laser induced experiments at 355 nm, such as laser-flash photolysis, photoacoustic and singlet oxygen 1O 2 phosphorescence detection, confirmed the formation of the excited triplet state of 1 with a quantum yield Φ T = 0.50 as the precursor for the generation of singlet oxygen 1O 2 ( Φ Δ = 0.16) and the isomeric α-pyran derivative ( 3 ), which was a reaction intermediate detected by NMR. In turn, the reaction of 1O 2 with 1 and 3 occurred with rate constants of 1.0 × 10 6 and 2.5 × 10 8 m −1s −1 to yield the oxygenated products 5 and 2 , respectively, indicating the relevance of the fixed s-cis configuration in the α-pyran ring in the concerted [2+4] cycloaddition of 1O 2. 相似文献
8.
Copper oxide is moderately active and selective in the oxidative dehydrogenation of n-butane. Selectivity to C 4 olefin is almost constant in the range of 200–520°C. The apparent activation energy determined between 200 and 360°C was 18.8 kcal/mol, and 9.2 kcal/mol at higher temperatures.
-. C4 200–520°C. 200–360°C 18,8 /, 9,2 /. 相似文献
9.
1-Dimethylamine-1-carba- closo-dodecaborane(1), 1-(CH 3) 2NH-1-CB 11H 11, can be smoothly demethylated with iodine in weakly alkaline solution to produce 1-methylamine-1-carba- closo-dodecarborane(11), 1-CH 3NH 2-1-CB 11H 11. The latter compound undergoes formylation with formaldehyde and iodine to give 1-hydroxymethylene-methylamine-1-carba- closo-dodecaborane(11). Further chemical transformations of both compounds are reported. 相似文献
10.
The membrane properties of the ganglioside GM1 (GM1)/dioleoylphosphatidylcholine (DOPC) binary system and GM1/dipalmitoylphosphatidylcholine (DPPC)/DOPC ternary system were investigated using surface pressure measurements and atomic force microscopy (AFM), and the effect of surface pressure on the properties of the membranes was examined. Mixed GM1/DPPC/DOPC monolayers were deposited on mica using the Langmuir-Blodgett technique for AFM. GM1 and DOPC were immiscible and phase-separated. The AFM image of the GM1/DOPC (1:1) monolayer showed island-like GM1 domains embedded in the DOPC matrix. There was no morphological change on varying surface pressure. The surface pressure-area isotherm of the GM1/DPPC/DOPC (2:9:9) monolayer showed a two-step collapse as in the DPPC/DOPC (1:1) monolayer. The AFM image for the GM1/DPPC/DOPC monolayer showed DPPC and GM1 domains in the DOPC matrix, and the DPPC-rich phase containing GM1 showed a percolation pattern the same as the GM1/DPPC (1:9) monolayer. The percolation pattern in the GM1/DPPC/DOPC monolayer changed as the surface pressure was varied. The surface pressure-responsive change in morphology of GM1 was affected by the surrounding environment, suggesting that the GM1 localized in each organ has a specific role. 相似文献
11.
The synthesis and structural characterization of tetra(1 H, 1 H, 2 H, 2 H-polyfluoroalkyl)silaneswith the same or different chain lengths C nF 2n+1 linked to Si (1 n6) is reported. When the synthesis was effected from chlorosilanes and fluorinated organomagnesiumor organolithium reagents, the trialkylsilanes were obtained. The last fluorinated chainwas introduced either via a fluoroalkyllithium reagent or by hydrosilylation of thetrialkylsilanes. Some properties and characterization by 1H, 19F and 29Si NMR spectroscopy of the1H, 1H, 2H, 2H-polyfluoroalkylsilanes are described. 相似文献
12.
At 25°C, I = 1.0 M (CF 3SO 3−Li ++CF 3SO 3H), [H +] = 0.034–0.274 M and λ = 453 nm, the rate equation for the oxidation of Ti(H 2O), 63+ by bromine was found to be: −d/[Br 2] T/d t= kK/[Br 2][Ti III]/[H +]+ K+ kK/[Br 3−][Ti III]/[H ++ K, where k = 9.2 × 10 −3 M −1 s −1 and K = 4.5 × 10 −3 M. At [H +] = 1.0 M, [Br −] = 0.05–0.4 M, the apparent second-order rate constant decreases as [Br −] increases. The pH-dependence of the oxidation of TiIII-edta by bromine is interpreted in terms of the change in identity of the TiIII-edta species as the pH of the reaction medium changes. The second-order rate constants were fitted using a non-linear least-square computer program with (1/k0edta)2 weighting into an equation of the form: k0edta =k1+k2K1[H+]−1+k3K1K2[H+]−2/1+K1[H+[H+−1+K1K2[H+]−2, with K1 and K2 fixed as earlier determined at 9.55 × 10−3 and 2.29 × 10−9 M, respectively, for the oxidation of bromine. k1=k2=(3.1±0.32)×103M−1s−1 k3=(2.3±0.45)×106N−1s−1. It is proposed that these electron transfer reactions proceed by univalent changes with the production of Br2.− as a transient intermediate. An outer-sphere mechanism is proposed for these reactions. The homonuclear exchange rate for TiIII-edta+TiIV-edta is estimated at 32 M−1 s−1. 相似文献
13.
The S 2-S 0 fluorescence excitation spectra ofxanthione (XT) and azulene (AZ) complexed with 1 or 2 molecules of the C 1 to C 10 n-alkanes and the C 1 to C 6 perfluoro- n-alkanes have been measured. The 1:1 complexes exhibit microscopic solvent shifts, Δ
gn, which are larger for the alkanes than the corresponding perfluoroalkanes, despite the larger molecular polarizability of the latter. The values of Δ
gn increase monotonically with carbon number of the adduct to C 10 in 1:1 n-alkane complexes with XT and to C 5 in 1:1 n-alkane complexes with AZ. However, Δ
gn exhibits no further increase beyond C 2 in 1:1 perfluoro- n-alkane complexes with XT and beyond C 3 in 1:1 perfluoro- n-alkane complexes with AZ. The results are interpreted in terms of a model in which the n-alkanes stretch out along the long axis of the chromophore and ‘wet’ its surface whereas the perfluoro- n-alkanes with carbon numbers 3 away from the surface of the chromophore and are ‘non-wetting’. 相似文献
14.
A variety of terminal chain modifications ( Y) were made on the diacetylenes in which X=C nH 2n+1, C 12H 25O and F, and Y=CH 2CH(Me)C 2H 5, COCH 3, C≡CC 5H 11, C nF 2n+1C nH 2n+1 and CH=CHCO 2C 3H 7. Mesomorphic properties were determined by hot stage polarizing microscopy and DSC. These were compared with those for the dialkyl analogues ( X=C mH 2m+1, Y=C nH 2n+1) and a series of 1- and 2-olefins ( Y=CH=CHC nH 2n+1 and CH 2CH=CHC nH 2n+1). The 1-olefin series showed wider range nematics than the dialkyl compounds, whereas the above modifications showed either narrow range nematic phases, no mesophase or higher melting temperatures. New transition temperature and enthalpy data are provided for some of the dialkyl and F-alkyl compounds previously reported, for comparisons. Preliminary birefringence data are also included along with the results of some heat and UV stability studies. 相似文献
15.
One-electron oxidation of the ferrous tris-PQ complex, a model for lipoxygenase, was attempted using oxidants such as •OH, N •3, Br •-2, Tl 2+ and TlOH +. •OH was found to react with the complex with a bimolecular rate constant of (3.9±0.6)x10 9dm 3mol -1s -1, a rate which is not very dissimilar to that for the reaction with the ligand PQ. However the product of the reaction was found to be a OH-adduct rather than a cation radical. No reaction was found to occur with N •3 or Br •-2. Both Tl 2+ and TlOH + reacted with the complex to form its oxidised species with rate constants of (7.0±1)x10 8dm 3mol -1s -1 and (4.0±0.8)x10 8dm 3mol -1s -1, respectively. From a comparison of the rate constants and the transient spectra it was concluded that the centre of oxidation is the ligand rather than the metal. 相似文献
16.
The far-UV (193 nm) laser flash photolysis of nitrogen-saturated isooctane solutions of 1,1-dimethylsiletane allows the direct detection of 1,1-dimethylsilene as a transient species, which (at low laser intensities) decays with pseudo-first-order kinetics (τ 10 μs) and exhibits a UV absorption spectrum with λ max 255 nm. Characteristic rapid quenching is observed for the silene with methanol ( kMcOH = (4.9 ± 0.2) × 10 9 M −1 s −1), tert-butanol ( kBuOH = (1.8 ± 0.1) × 10 9 M −1 s −1) and oxygen ( kO2 = (2.0 ± 0.5) × 10 8 M −1 s −1). The Arrhenius activation parameters for the reaction with methanol have been determined to be Ea = −2.6 ± 0.6 kcal mol −1 and log A = 7.7 ± 0.3. 相似文献
17.
The molecular structure of 4,4′-sulfanidyl-bis-thiophenol (C 12H 10S 3) has been determined by gas electron diffraction. Assuming identical geometry and D2h local symmetry for ---SC 6H 4S--- moieties, the following bond lengths ( rg) and bond angles were obtained: C---H = 1.101 ± 0.005, S---H = 1.388 ± 0.019, (C---C) mean = 1.400 ± 0.003, (S---C) mean = 1.778 ± 0.004 Å, C ar---S---C ar = 103.5 ± 1.3, C---C(S)---C = 120.4 ± 0.3, C(H)---C(H)---H = 119.1 ± 0.9 and C---S---H = 94.6 ± 3.1°. Two ratational forms were found to reproduce the experimental data, characterized by dihedral angles of the benzene rings with respect to the C arSC ar plane; 1 = 67.8 ± 2.0°, 2 = 4.5 ± 7.2°, and 1 = 69.4 ± 2.0δ, 2 = −26.6 ± 7.1°. Identical signs of 1 and 2 indicate that the two benzene rings are rotated in the same direction about the respective S central---C axes. 相似文献
18.
Volume changes on mixing of ternary liquid mixtures of N,N-dimethylformamide and diethyl ketone with 1-alkanols have been measured as a function of composition at 303.15 K. The alkanols include 1-propanol, 1-butanol, 1-pentanol and 1-hexanol. The measured VE values are negative in the mixtures of N,N-dimethylformamide, diethyl ketone and 1-propanol, or 1-butanol. The VE data exhibits an inversion in sign in the mixture containing 1-pentanol and positive excess volumes are observed in the mixture containing 1-hexanol. The measured data are compared with predicted values based upon empirical relations. The excess volume for the binary mixture of N,N-dimethylformamide with diethyl ketone has been measured over the entire range of composition at 303.15 K. The VE values are negative for the binary mixture. 相似文献
19.
In this paper the results of detection of higher excited states of p-fluorotoluene in the gas phase are presented. Within a laser scanning range of 547.0–570.0 nm (3+1) RMPI spectra are obtained, and some vibrational structures on the third electronically excited valence state are observed. According to the polarization characteristic of the multiphoton transition the symmetry of the electronic state is determined as A 1+B 1+3pB 2. Correlated to excited states of benzene, the results show that A 1+B 1 corresponds to 1E 1u and 3pB 2 to 3p 1A 2u. It indicates that the double degeneracy of 1E 1u state does not yet degrade in p-fluorotoluene. Moreover, it occasionally degenerates with 3p 1 A 2u. Furthermore, the electron distribution in the phenyl ring maintains the symmetry of the D 6h point group consistently like in benzene. 相似文献
20.
通过共沉淀法制得类球形锂离子电池正极材料LiNi 1/3Co 1/3Mn 1/3O 2,并用非水相共沉法对其进行CoAl 2O 4包覆得到LNCMO(x). 采用X射线衍射(XRD)、扫描电子显微术(SEM)和透射电子显微术(TEM)测试材料的结构和观察材料形貌. 结果表明,CoAl 2O 4在材料表面形成8 nm均匀包覆层,未改变主体材料的结构. 电化学性能测试表明,1%(by mass)CoAl 2O 4包覆量的LiNi1/3Co1/3Mn1/3O2材料(LNCMO(1))高充电电压(3.0 ~ 4.6 V,150 mA·g -1)100周期循环放电容量保持率为93.7%(无包覆LNCMO(0)保持率为74.4%);55 °C高温100周期循环容量保持率为77%(无包覆LNCMO(0)保持率17%). XRD和电感耦合等离子体原子发射光谱(ICP-AES)测试表明,CoAl 2O 4包覆的LNCMO(x)材料可有效地减缓材料中Mn离子在电解液的溶解,提高材料结构稳定性和热稳定性. 相似文献
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