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991.
Quang Shen 《Journal of Molecular Structure》1978,49(2):337-343
The molecular structure of bis(chloromethyl) dimethyl silane has been investigated in the gas phase at a nozzle temperature of 60° C. The molecules exist mainly in the GG form with the presence of 30% (+10%, ?20%) AG form. The values of the principal distances (ra) and angles with estimated error limits of 2σ are r(C-H) = 1.093 (0.009) Å, r(C-Cl) = 1.801 (0.019) Å, r(Si-C) (the average Si-C bond) = 1.875 (0.009) Å, ∠(CSiC) = 109.5°, ∠(SiCCl) = 110.5° (0.4), ∠(CCH) = 112.5° (1.8) and φ (the gauche torsion angle relative to 0° for the anti form) = 117.4° (3.8). 相似文献
992.
Paul A. Wender Scott McN. Sieburth Joseph J. Petraitis Sunil K. Singh 《Tetrahedron》1981,37(23):3967-3975
Treatment of 1,2-(E,E)-di(1-buta-1,3-dienyl)cyclohexanol (21) with potassium hydride in tetrahydrofuran at room temperature resulted in the facile formation of a 14-membered ring dienolate which on kinetic protonation provided cyclotetradeca-3,5,7-trien-1-one. This novel rearrangement which provides the basis for an efficient, eight unit ring expansion method was also observed when 5,8-dimethyl-5-hydroxy-1,3,7,9-decapentaene (28), the acyclic analogue of 21, was treated with potassium hydride in tetrahydrofuran. Methodology for the preparation of 21 and 28 including the preparation of 1-lithio-1,3-butadiene is also described. 相似文献
993.
Pleiadiene and other similar compounds have been studied by the semi-empirical SCFMO method of Pariser, Parr and Pople using the core resonance integral value developed by Lo and Whitehead, Dewar et al. and Yamaguchi et al. It has been found that π*←π transitions predicted by the methods of Lo and Whiteheadand Dewar et al. suitable for the prediction of ground state properties are also in good agreement with experimental results where available and comparable to those predicted by the method of Yamaguchi et al. developed for the prediction of spectral transitions. The resonance stabilization of the molecules 3,4.5,7,8 and 9 have also been studied. It is found that ethylinic linkage across the naphthalene moity in pleiadiene increases the resonance energy of the final compound, in contrast to our previous observation, i.e. ethylinic linkage across the naphthalene moiety reduces the resonance energy of the final compound. 相似文献
994.
Alkaline aqueous solutions of β-naphthylamine show the edge effect; a decrease in the relative intensity or emission from the anion (RNH?) and the neutral molecule (RNH2) on red-edge excitation (REE) is observed. The nature of quenching of the neutral molecule by OH? ions also changes on REE. It is suggested that on REE, participation of some non-promoting out-of-plane modes slows down the proton-transfer rate in the excited state. 相似文献
995.
Several band contours have been successfully resolved in the high-resolution IR spectrum of pentacarbonyl(thiocarbonyl)chromium(0) vapor at ~312 K. However, PQR separations are only clearly discernible for the three v(CO) fundamentals (v1,v2 and v16). The good agreement between the observed and calculated PR separations of the two a1v(CO) modes (v1 and v2) verifies the C4v prolate symmetrical top geometry of the molecule. From band shape analyses, the Coriolis coupling constants of the ev(CO) mode (v16) and the e δ (CrCO) mode (v17) are estimated to be —0.45 ± 0.05 and —0.80 ± 0.15, respectively. 相似文献
996.
Variable temperature NMR spectroscopy was used to study the conformational behavior of [2.2](2,5)furanoparacyclophane (1), [2.2](2,5)furano(1,4)naphthalenophane (2) and [2.2](2,5)furano(9,10)anthracenophane (3). While the method was useful in studying 1, it was not adequate for 2 and 3. Variable temperature UV absorption and fluorescence emission studies provided information on the conformations of 2 and 3. The UV absorption and emission spectra of 1 were blue-shifted relative to their ambient temperature spectra. Those of 2 were not shifted at all and those for 3 were red-shifted. The data is consistent with an anti-orientation of the aromatic rings in 2 both at ambient and low temperture. The aromatic rings in 3 are perpendicular to one another at low temperature and probably at room temperature as well. Exiplex bands were absent in the room temperature emission spectra of 1, 2 and 3 as well as the low temperature spectra of 2 and 3. An exciplex band was observed in the low temperature emission spectrum of 1. 相似文献
997.
The preparation and properties of horseradish peroxidase covalently bound to polystyrene beads are described. A flow procedure for the spectrofluorimetric determination of hydrogen peroxide down to 1 ng ml-1, with homovanillic acid as substrate, has been developed. 相似文献
998.
The effects of dissolved electrolytes on the structure of liquid formamide have been investigated by Raman spectroscopy. The spectral features are dependent on the concentration and nature of the dissolved electrolyte and are discussed in terms of direct electrolyte formamide interactions. Two vN—H bands, arising from ion—formamide species, have been observed superimposed on the spectrum of residual liquid formamide. The results lend further support to the interaction model for electrolytes in liquid formamide previously proposed by us on the basis of nuclear magnetic resonance and infrared spectral data. 相似文献
999.
Hydrogen bond stretching force constants in crystals of imidazole, urea and cyanuric acid are calculated using both a modified CNDO/2 method and a constrained least squares fitting of interatomic pair potentials to the lattice vibrations. Results show that the modified CNDO/2 method gives closer agreement with the experimentally derived force constants than the normal CNDO/2 parameterization. 相似文献
1000.
Studies of the 13C N.M.R. spectra of the series RhX[P(Ch2CH2CHCH2)3] and RhX[P(CH2CH2CH2CHCH2)3] where x Cl or Br have revealed that (a) the J(103Rh-13C) (olefin) for the complexes studied is only ? that found for square-planar complexes, and (b) the fluxional character in the olefinic carbons observed for the compounds RhX[P(CH2CH2CHCH2)3] is related to the partial rotation of the olefin about the rhodium-olefin bond. 相似文献