Acta Crystallographica Section E Structure Reports Online (Impact Factor: 0.35). 10/2008; 64(Pt 10):o2001. DOI: 10.1107/S1600536808030250
Source: PubMed

ABSTRACT The asymmetric unit of the title compound, C(20)H(24)O(6), contains two mol-ecules that are identical within standard deviations concerning bond lengths and angles as well as their conformations. In the crystal structure, weak C-H⋯O inter-actions help to consolidate the packing.

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    ABSTRACT: Reactions of p-nitrophenylchlorocarbene (PNPCC) with various dibenzo crown ethers produce O-ylides and π-complexes; the reactions can be followed via the spectral signatures of the carbene and the products. The O-ylides form most rapidly, but over time they decay in favor of the more stable π-complexes. Extensive computational studies support and refine appropriate structural and mechanistic conjectures. Reactions of PNPCC with monobenzo crown ethers afford only the spectral signatures of O-ylides; monobenzo π-complexes are either not formed in significant concentrations or are spectroscopically silent.
    The Journal of Physical Chemistry A 08/2014; 118(32). DOI:10.1021/jp506154s · 2.78 Impact Factor
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    ABSTRACT: The co-crystal, C7H9N4O2 (+)·ClO4 (-)·C20H24O6·3.25H2O, consists of theobrominium (3,7-di-methyl-2,6-dioxo-1H-purin-9-ium) cations, perchlorate anions and dibenzo-18-crown-6 and water mol-ecules. The crown ether is in a bent conformation, in which the planes of the aromatic rings subtend an angle of 63.7 (1)°. Inter-molecular O-H⋯O hydrogen bonding between the water mol-ecules and the O atoms of the cyclic ether delimit an empty space reminiscent of a hollow cage. The water mol-ecules are additionally linked to the cations by N-H⋯O hydrogen bonding. One of the positions of the water molecules is occupied only fractionally (25%) and is located outside this framework.
    Acta Crystallographica Section E Structure Reports Online 07/2013; 69(Pt 7):o1027. DOI:10.1107/S1600536813014463 · 0.35 Impact Factor
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    ABSTRACT: Density functional theoretical calculation was performed to understand the isotopic fraction of zinc in the nano cavity of different crown ethers and crown ethers anchored on solid resin matrix. The structure, energetic, thermodynamics, and vibration IR spectra were also evaluated. The gas phase binding energy of Zn2+ with crown ether of varied cavity can be correlated with NPA charge transfer but no such correlation is obtained with the fraction of electron transfer, Delta N. The reduced partition function ratio (RPFR) of complexes of Zn2+ ion with different solvents, crown ethers, and grafted crown ethers was also computed to predict the isotope separation factor of the Zn2+ ion. The present study reveals that with increasing cavity size of the crown ether the RPFR was found to be decreased leading to a high value of isotope separation factor as observed in the experiments. An attempt was made to correlate the calculated RPFR and separation factor with binding energy of different zinc-crown ether systems. Further, it is shown that the smaller the solvation energy of the metal ion the higher will be distribution constant of Zn2+ ion as confirmed by experiments indicating solvents with low dielectric constant should be used for chromatographic separation process. The present study should be useful in screening the nano cavity based grafted resin and for future development of new grafted materials for Zn and other isotope separation.
    Journal of Chemical & Engineering Data 08/2014; 59(8):2472-2484. DOI:10.1021/je5002285 · 2.05 Impact Factor

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