meantimc the first successful crystal structure analysis of a "cobaltocenium-Angiw Ciiem. Int Ed. Engl. 1995, 34, No. 11 VCH Verlag.~gesrllsciiaft mbH, 0-6945'1 Weinheim. 1995 Oj70-0833,'95/1111-1201 B l~l.Ofl+ ..?j:(I
WaterÈmethanol and waterÈacetonitrile, which show exothermic and endothermic mixing, respectively, represent good contrast in non-ideality of a binary mixture. The microscopic structure observed through the mass-spectrometric analysis of clusters isolated from solution also shows good contrast between these binary mixtures as follows : (1) methanol molecules have substitutional interaction with water clusters, while acetonitrile molecules have additional interaction with water clusters ; (2) the clustering of methanol molecules are promoted in the presence of water ; on the contrary, the acetonitrile clusters are disintegrated in the presence of water. Such Ðndings could partially explain the non-ideality of these binary mixtures on the basis of the cluster structures.
A hydrothermal procedure is used to prepare the molecular sieve Al2 (CH3PO3)3 (1). This compound has a new three‐dimensional framework, in which one six‐coordinate and two four‐coordinate Al centers are bound to the CH3PO3 units. The channel walls of the micropores of 1 are probably not lined with O atoms but with methyl groups.
Microporous aluminum methylphosphonates, AlMepO-α and
-β, prepared by different procedures, were
characterized mainly using 27Al, 31P, and
13C MAS NMR, TG-DTA, and IR. The MAS NMR spectra
were
consistent with the crystal structures determined by the single-crystal
X-ray structural analysis published
previously. All the 31P NMR signals were reasonably
assigned using an assumed correlation between
31P
chemical shift and the mean Al−O−P angle around the phosphorus
sites. Nitrogen adsorption isotherms of
AlMepO-β degassed at elevated temperatures were of type I, while
those of AlMepO-α gave two plateaus in
the low relative pressure region. The stepwise adsorption was
explained by a packing change of the adsorbate
on adsorption. The pore diameter calculated from the maximum
nitrogen adsorption capacity was consistent
with adsorption of 2,2-dimethylpropane but was larger than the size
expected from the crystal structure of
both the compounds. The water vapor isotherm was type II in the
low relative pressure region, confirming
the hydrophobic nature for both compounds. AlMepO-α indicated no
apparent adsorption of water into the
channel, but AlMepO-β showed a sudden adsorption of water at
P/P
0 ≈ 0.7. The difference in
the water
vapor isotherms between the compounds was explained based on the
relationship of the size of the water
clusters formed and the shape of the adsorbent channel.
An effective one-electron quantum chemical method was applied to enumerate the conformers of unbranched aliphatic alkanes. The results obtained for butane, pentane, hexane, and heptane were utilized to derive four rules with which the number and sequences of the existing conformers up to undecane could be reproduced. The validity of the rules was confirmed at Hartree-Fock and second-order Moeller-Plesset levels too. Full ab initio conformational analyses were performed for the butane, pentane, hexane, heptane, and octane molecules. The rules demonstrate that the most important factors governing the conformational behavior of unbranched aliphatic alkanes are the nonbonded repulsive-attractive (van der Waals) interactions between the hydrogen atoms attached to the carbon atoms at positions 1,4; 1,5; 1,6; and 1,7. The calculated gasphase standard heats of formation of the unbranched aliphatic alkanes closely matched the experimental values.
The hydrothermal conversion of Na-magadiite in tetramethylammonium hydroxide (TMAOH) and 1,4-dioxane to form a new layered silicate structure, assigned as KLS1, is described. Total conversion of Na-magadiite to KLS1 was achieved in a short reaction time of 4 hours. The nature of the new silicate structure was characterized by using 29 Si MAS NMR and found to contain predominantly Q 3 type (SiO) 3 -Si-OH building units.
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