摘要:

Abstract“Truncated” [1.1.1.1] pagodanes like the [1.1.0.0]and [0.0.0.0] homologues3 and 4 (EStr= 146.1 – 171.5 kcal mol−1, MM2) are potential precursors of unusual unsaturated homoconjugated radical cations and σ‐bishomoaromatic dications. Attempts are presented toward the synthesis of 3 ‐ starting out from [1.1.1.1] pagodane‐4,9‐dione 9 and diaza [2.2.1.1]pagodadiene 11 by cycloelimination (unsuccessful) and by Favorskii‐type ring contraction methodologies. Control experiments with the model diketone 19 documented the limitations for α,α′‐difunctionalization of 9 as the prerequisite for one‐pot double Favorskii‐type ring contraction. Ade novosynthesis for such α,α′‐disubstituted derivatives of 9(54) was not sufficiently expeditious to open a practical access to 3. Sequential double bridgehead hydroxylation of 9, successfully practized with model 19, similarly suffered from inherent cage effects and allowed only limited yields of [1.1.1.0] pagodanone 10

ISSN:0009-4536    

DOI:10.1002/jccs.199400001

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractUnder El conditions, substituents onN‐alkylpyrroles affect fragmentation of the alkyl groups. The electron‐withdrawing character of the cyano group retarded formation of aN‐methylene cation, and a labile substituent, i.e., ‐CHO, ‐CH2COOMe, competed with anN‐alkyl group to be a initial fragmentation center, MNDO calculation of the heat of formation of possible fragment ions showed that protonated pyridine is the most stable among the is

ISSN:0009-4536    

DOI:10.1002/jccs.199400002

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractDynamic and static scattering of light was employed to investigate mixed micelles of two homologous anionic surfactants‐sodium octyl sulfate and sodium hexadecyl sulfate, above the phase boundary temperature and critical micelle concentrations (cmc). The results indicate that the mixed micelles change from prolate to sphcrical as the molar ratio SOS/SHS increases from 1 to 8. Below 1 or above 8, the formation of micelles is due to one surfactant dissolving the othe

ISSN:0009-4536    

DOI:10.1002/jccs.199400003

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractUnder various basic solutions and reaction durations, 3‐substituted 4‐formyIsydnones and nitroalkanes containing α‐active hydrogen (e.g. nitromethane and nitroethane) are converted to β‐nitroalcohols, nitroalkenes and dinitroalkanes. β‐Nitroalcohols are obtained only by electrochemical reaction on an electrogenerated base (EGB). The mechanism of overall reaction steps in particular

ISSN:0009-4536    

DOI:10.1002/jccs.199400004

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe reaction of (η5‐cyclopentadienyl)(η4‐1,3‐diphenylcyclobutadiene)cobalt (I) with excess Cr(CO)3py3in BF3OEt2yielded two identified heterometallic compounds. CompoundsIIandIIIwith one and two phenyl rings complcxed with Cr(CO)3fragment(s), respectively. These compounds were characterized by mass, infrared,1H and13C NMR spectra and elemental analysis. The crystal structure ofIIwas determined. The Cr(CO)3fragment bends inward toward the cyclobutadicne ring due to its electron‐withdrawing ability, in accord with Hunter's postulate. A sharp line due to the non‐complexed phenyl ring was observed in the1HNMR spectrum, which implies that five protons are magnetically equivalent. The chemical shifts of two protons of the cyclobutadiene ring decreased fromItoIIthen toIII, possibly because of diminished deshielding effect from the phenyl ring in (ar

ISSN:0009-4536    

DOI:10.1002/jccs.199400005

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe chemical environments of europium‐exchanged NaX (Si/Al =1.16) and NaY (Si/Al = 2.29) zeolites have been investigated by means of129Xe NMR and isotherm measurements of adsorbed xenon. EuNaX and EuNaY samples with varied concentrations of Eu cations were subjected to diverse chemical and thermal treatments, namely dehydration, reduction, oxidation, and re‐reduction.Thermal analyses of hydrated EuNaX and EuNaY samples indicate that both the structural stability and the saturation concentration of water increase with increasing Eu content. For dehydrated EuNaY zeolites, the Eu3+cations tend to replace Na+ions at S2 sites and tend to be located in framework supercages; similar behavior is found for Eu2+ions after reduction. After subsequent oxidation, Eu3+ions migrate from supercages into small sodalite and/or D6R cages; similar results were deduced for samples after re‐reduction. In contrast to the behavior observed in EuNaY, Eu3+ions tend to exchange for Na+ions in the sodalite and/or D6R cages in dehydrated EuNaX zeolites, regardless of the thermal treatment; this behavior is ascribed to the existence of unlocalized S3 Na+in EuNaX sa

ISSN:0009-4536    

DOI:10.1002/jccs.199400006

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractBis‐citrato1a‐d, bis‐citramalato2and bis‐malato3germanate(IV) complexes were synthesized from germanium dioxide and citric acid, citramalic acid and malic acid respectively and were identified with IR, NMR and elementary analysis. Crystal 1a is triclinic, space group P1 with a = 7.919(2), b = 7.968(3), c = 9.605(3) Å, α = 94.25(3), β = 108.03(2), γ= 113.05(3)°, Z = 1, and the final residue, R(F), is 0.033 for 2583 reflections. Crystal 2 is monoclinic, space group C2 with a = 10.226(4), b = 12.802(4), c = 6.141(1) Å, β = 100.75(2)°, Z = 2, and the final residue, R(F), is 0.034 for 934 reflections. Both1aand2have slightly distorted octahedral structures with citrate or citramalate ions as a tridentate ligand that forms five‐, six‐ and seven‐membered rings with the central metal. There is a two‐fold axis through the central atom of compound2instead of the inversion center of1a. Same structures for these six complexes are indicated because the spectral patterns of the other four compounds,1b‐dand3, are similar to

ISSN:0009-4536    

DOI:10.1002/jccs.199400007

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractWe describe a method to calculate the distribution of sizes of fine crystals from pure powder‐diffraction profile using a method of maximum entropy (MAXENT). We apply a Monte‐Carlo technique of simulated annealing to seek a global minimum of the error surface in fitting this diffraction profile. We consider pure diffraction profile (instrument de‐convoluted) of a powder specimen without lattice imperfection to a significant extent. Under these circumstances, the distribution of the pure diffraction profile can be attributed to the distribution of crystallite size. We applied this method to three cases of crystal sizes having a highly inhomogeneous distribution with certain noise‐tolerance. The results agree well with synthetic data of diff

ISSN:0009-4536    

DOI:10.1002/jccs.199400008

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractFurylpyridines, thienylpyridines, and imidazolylpyridines were obtained regioselectively in 40‐67% yields from the reaction of heteroaryllithiums withN‐ethoxycarbonylpyridinium chloride orN‐ethoxycarbonyl‐3‐methylpyridinium chloride in the presence of Cul in a catalytic amount at −78 °C or −50°C, then followed by oxidation. The regioselectivity of this reaction depended upon temperature of the reaction and the nature of het

ISSN:0009-4536    

DOI:10.1002/jccs.199400009

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractVarious crown ethers were used as phase‐transfer catalysts for free radical polymerizations of some water‐insoluble vinyl monomers such as acrylonitrile, methylmethacrylate and styrene with persulfate as initiator. The catalytic abilities of these crown ethers for free radical polymerization of acrylonitrile with S2O82−ion as an initiator were in the order: 18‐crown‐6>15‐crown‐4>12‐crown‐4>benzo‐15‐crown‐5>dibenzo‐18‐crown‐6. Among various persulfates such as Na2S2O8K2S2O8and (NH4)2S2O8, ammonium persulfate was the optimum initiator for the polymerization of acrylonitrile catalyzed by 18‐crown‐6 or 15‐crown‐5. Among the organic solvents used, chloroform seems to be the best solvent for the catalytic polymerization of acrylonitrile. An apparent activation energy of 72.9 kJ mol−1was observed for the polymerization of acrylonitrile. The catalytic reaction rates of free radical polymerization for these hydrophobic vinyl monomers were in the order: acrylonitrile>methylmethacrylate>styrene>isoprene. Effects of concentrations of crown ether, initiator, and nitrogen on the polymerization of

ISSN:0009-4536    

DOI:10.1002/jccs.199400010

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY