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131.
David J. Wesolowski Donald A. Palmer George M. Begun 《Journal of solution chemistry》1990,19(2):159-173
Gibbsite, Al(OH)3, solubility studies in aqueous NaCl solutions at pH 9 demonstrate that the aluminate anion forms a strong complex with the neutral Bis-tris molecule 2,2-Bis(hydroxymethyl)-2,2,2-nitrilotriethanol, at low temperatures. The logarithm of the molal concentration quotient for the reaction
相似文献
132.
Leslie D. Field Adrian V. George Trevor W. Hambley Peter Turner Brian J. Wallace 《Journal of organometallic chemistry》1997,540(1-2):95-99
Reaction of cis-[FeH2(dmpe)2](1) with diphenylbutadiyne results in an insertion into both of the iron-hydride bonds to form an iron metallocycle. Spectroscopic and crystallographic data of [Fe(PhHCC2CHPh)(dmpe)2] (3) show 1,4-diphenylbutatriene is symmetrically bound to the metal via the central double bond. The reaction to form the metallocyclic complex is greatly accelerated by application of external pressure. A 41% yield of (3) is isolated after two days at atmospheric pressure or after approximately 75 min at 800MPa. 相似文献
133.
[reaction: see text]. The reactions of aryl aldehydes with 2 equiv of arylacetylenes in the presence of boron trichloride yield (E,Z)-1,3,5-triaryl-1,5-dichloro-1,4-pentadienes. Reactions carried out in the presence of boron tribromide generate the corresponding (Z,Z)-1,3,5-triaryl-1,5-dibromo-1,4-pentadienes. 相似文献
134.
Shawn R. Hitchcock George P. Nora David M. Casper Joseph D. Wiman Jeromy T. Bentley Carrie Stafford Michael D. Squire 《Journal of heterocyclic chemistry》2002,39(5):1113-1115
A several novel 1,3,4‐oxadiazinan‐2‐thiones have been synthesized by the cyclization of β‐hydrazino‐alcohols with either carbon disulfide or 1,1′‐thiocarbonyldiimidazole (TCDI). 相似文献
135.
Andrzej J. Treszczanowicz George C. Benson 《The Journal of chemical thermodynamics》1977,9(12):1189-1197
Excess volumes VE measured at 298.15 K in a successive-dilution dilatometer are reported for binary mixtures of the n-alkanols C1 to C4 + n-heptane. For ethanol +, and n-butanol + n-heptane, the measurements were extended to high dilutions of alkanol. VE is positive for all of the mixtures but decreases rapidly in magnitude for increasing chain length of the n-alkanol. The results were used to estimate the excess partial molar volumes of the components. 相似文献
136.
Oxidative cyclization of isomeric 5,6-dihydroxyalkenes of type derived from neryl and geranyl acetates with Cr(VI) oxo species afford cis-THF diols of type (syn addition across the double bond) with >99.5% stereospecificity. 相似文献
137.
Bao J Baker RK Doss GA Kayser F Kotliar A Miao S Parsons WH Rupprecht KM 《Organic letters》2002,4(11):1871-1873
[reaction: see text] Pentacyclic triterpenoid natural product correolide (1) was converted to ketone 2 via ozonolysis. An unusual fragmentation reaction of ketone 2 with LiCl was discovered. This reaction is general among several similar substrates examined and appears to be specific for the correolide-type E-ring structure (ketone). A mechanism involving a retroaldol reaction, a nucleophilic opening of the epoxide, and a subsequent acetoxy elimination reaction was proposed. 相似文献
138.
Martina Schfer Ehmke Pohl Karen Schmidt-Bse George M. Sheldrick Rolf Hermann Adriano Malabarba Marino Nebuloni Giancarlo Pelizzi 《Helvetica chimica acta》1996,79(7):1916-1924
The crystal structure of a glycopeptide antibiotic A–40926 aglycone was investigated by X-ray analysis at ?120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) Å. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F > 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin. 相似文献
139.
Takeshi Kikuchi George Nmethy Harold A. Scheraga 《Journal of computational chemistry》1989,10(3):287-294
The method presented earlier [T. Kikuchi, G. Némethy, and H.A. Scheraga, (1986) J. Comput. Chem. 7 , 67] for the classification of patterns of the three-dimensional folding of a covalently crosslinked polypeptide chain has been extended to nonplanar proteins. The procedure described earlier was applicable only to proteins termed planar, i.e., with a connexity of the crosslinks (e.g., disulfide bonds) that can be represented in a planar diagram. The procedure described in the present work is applicable to any (planar or nonplanar) pattern of crosslinking. The classification is based on a systematic and objective method of enumeration of spatial geometric arrangements of loops (SGAL) using no information other than the location of the disulfide bonds in the amino acid sequence. Various SGAL classes correspond to the presence of different ways of mutual penetration of loops, called thrustings and entanglements. Information on SGAL classes can be of use in structural predictions of folding patterns of proteins. 相似文献
140.
Two points involving molecular structure have been investigated using mass spectrometry. First, mass spectra have been obtained that indicate a rapid means for differentiating bimolecular compounds from other structural isomers. Second, the mass spectrometric method has been used to evaluate bonding within bimolecular compounds. Quinone compounds have been reacted with dhydroxybenzene compounds to produce quinhydrone products, and upon mass spectrometric analysis, the quinhydrones decompose to regenerate derivatives of the starting materials. Evaluation of the decomposition products suggests that the hydroxyl hydrogens are involved in a resonance structure, and while in symmetrical quinhydrones, the hydroxyl hydrogens are probably associated equally with each reactant, unsymmetrical quinhydrones generate an unbalanced electronic distribution that eliminates the complete equivalency of the hydrogens. 相似文献
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