ISSN:0018-019X    

DOI:10.1002/hlca.19780610102

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

ISSN:0018-019X    

DOI:10.1002/hlca.19780610103

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractThe photoelectron spectrum of tetrakis (methylidene)cyclobutane (1, ‘[4]radialene’) is reported. The electronic states of1+are assigned on the basis of model calculations and with reference to related systems.Jahn‐Telleractivity in the degenerate states is discussed. A failure of the simple LCBO‐model for the π(eg)‐orbital of1is noted and traced to the fact that this orbital, though having a symmetry‐equivalent π*‐counterpart, does not interact with it. This feature is confined to [4n]radialenes; their total π‐energies are therefore higher than those of the other members. It is shown that radialenes, in principle, do not constitute a class analogous to that of the linear polyenes a

ISSN:0018-019X    

DOI:10.1002/hlca.19780610104

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractThe He(Iα) and He(IIα) spectra of tetrafluorobutatriene3(F) have been recorded for comparison with those of butatriene3(H).Ab initiodouble‐zeta basis self‐consistent field (SCF) and configuration interaction calculations on butatriene show that, contrary to previous assignment, no shake‐up band is expected to appear in the 9–10 eV energy range of the photoelectron spectrum. Further, such SCF calculations on tetrafluorobutatriene support the use of the perfluoro effect in assigning the purely π orbital ionizations. It is argued that3(F) is a key compound for the study of the perfluoro effect. This is supported by a qualitative comparison of its photoelectron‐spectroscopic results with those of other perfl

ISSN:0018-019X    

DOI:10.1002/hlca.19780610105

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractStationary points of the INDO energy hypersurface for various orientations of ethylene in external electric fields of the strengthF=0, 2, 4, 6, 8 and 10 × 1010V m−1were found and their characteristics studied by the force constant matrix analysis. Energies, structural parameters, charges,Wibergindices and dipole moments are presented. The only stable orientation of the ethylene molecule is that for which the CC bond is parallel to the field direction up toF=6 × 1010V m−1(orientation (a) inFig. 1). Above this value the molecule is structurally unstable and it decomposes to the hydride anion and the C2H3+cation. Rotational instability was found for two perpendicular orientations of the CC bond with respect to the field vector, in which the field vector was parallel and perpendicular to the molecular plane. Pseudorotations with negative eigenvalues of force constant matrices lead to the stable orientation (a). No stationary points were found when the angle between the CC bond and the field vector was between 0 and 90°. The five longest wavelength vibrational bands are presented for selected orientations and fie

ISSN:0018-019X    

DOI:10.1002/hlca.19780610106

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractWe have measured the stability constants of the cryptate complexes formed by ligands1–4with alkali, alkaline‐earth, transition metal and toxic heavy metal cations. Stabilities and selectivities of complexation of the alkali and alkaline‐earth cations are less pronounced in1–4than in the parent compounds5and6and decrease as the number of nitrogen sites increase. Remarkable complexation properties are found towards transition metal and toxic heavy metal cations. The intramolecular cavity of ligands1–3is too large for small cations like Co2+, Ni2+, Zn2+so that the complexes formed are comparatively weak; however these cations are strongly complexed by ligand4whose intramolecular cavity has a much smaller size, compatible with their ionic radius. On the other hand, ligands1–4all form highly stable cryptates with Cd2+, Hg2+, Pb2+. Thus by the combined operation of the two structural parameters, cavity size and nature of the binding sites, cryptands2et3present very high selectivities for the complexation of these toxic heavy metal cations with respect to the biologically important ones Na+, K+, Mg2+, Ca2+, Zn2+. The selectivities of ligand2for Cd2+, Hg2+and Pb2+with respect to Zn2+are as high as 106, 1018and 109respectively. They are much more pronounced than those of previously known complexing agents. Cryptands like2and3thus present a unique selectivity sequence of special interest indetoxication(decorporation, depollution). Further structural elaboration may allow to design ligands which present a given selectivity pattern of potential use in “cryptatotherapy” and “environment pollution control”. The results also provide evidence for the existence, at low pH, of protonated complexes which probably participate in an acid catalysed process for dissociati

ISSN:0018-019X    

DOI:10.1002/hlca.19780610107

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Rearrangements of the Phenylthio Group of Trimethylsilyl‐enolethers of α,α‐Dialkylated α‐Phenylthio‐ketonesTrimethylsilyl‐enolethers of α,α‐dialkylated α‐phenylthio‐ketones undergo a photochemically induced 1,3‐phenylthio shift leading to isomeric enolethers in high yields. The rearrangement can also be carried out under thermal conditions, but the resu

ISSN:0018-019X    

DOI:10.1002/hlca.19780610108

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractDetailed cation scavenger studies in pulse‐irradiated pure, liquid CCl4reveal that the 500 nm absorption has both, neutral and cationic characteristics, and that CCl4+must be the precursor. It is shown that all experimental results are compatible with the following ion neutralisation mechanism: CCl 3++ Cl−→ (CCl 3+· Cl−) → CCl4.The 500 nm band is assigned to the CCl3+‐cation (free or complexed). Its neutralisation therefore does not occur on ion recombination, but is delayed by the life time of the ion pair: τ½(ion pair) = 33 ± 3 ns at −22°C with activation energy of 10.9 ± 2.1 kJ/mol. Possible reasons for the ion pair stabilit

ISSN:0018-019X    

DOI:10.1002/hlca.19780610109

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Diazo‐Group Transfer to Active Methylene Compounds Using Azidinium SaltsDie Synthese von Diazoverbindungen durch Diazogruppenübertragungen auf durch Carbonyl‐, Cyan‐ und Nitro‐Gruppen aktivierte Methylenverbindungen mit den Azidiniumsalzen 2‐Azido‐3‐äthyl‐benzthiazolium‐tetrafluoroborat und 1‐Äthyl‐2‐azido‐pyridinium‐tet

ISSN:0018-019X    

DOI:10.1002/hlca.19780610110

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Diazo‐Group Transfer to Hydroxy‐arenes and Hydroxy‐hetarenes Using Azidinium SaltsDie Einführung der Diazogruppe mit 1‐Äthyl‐2‐azido‐pyridinium‐tetrafluoroborat und 2‐Azido‐3‐äthyl‐benzthiazolium‐tetrafluoroborat in Hydroxybenzole, Hydroxynaphthaline und einige Hydroxy‐hetarene wird beschrieben. Der Anwendungsbereich dieser Methode im Vergleich mit der Tos

ISSN:0018-019X    

DOI:10.1002/hlca.19780610111

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY