摘要:

AbstractA linear correlation was found between the proton chemical shifts of the vinyl protons inm/p‐substituted styrenes and cinnamic acids and the π‐electron densities of the corresponding carbon atom, calculated by the simple LCAO‐MO procedure, using standard values for the perturbation para

ISSN:0018-019X    

DOI:10.1002/hlca.19670500802

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

摘要:

AbstractA vapour pressure osmometer for the determination of number‐average molecular weights is described. With this improved design 10−4M solutions can be measured with a standard deviation of 1.3% (carbon tetrachloride, 30°C). Molecular weight determinations up to 160000 (± 7.5%; polystyrene in carbon tetrachloride) are pres

ISSN:0018-019X    

DOI:10.1002/hlca.19670500803

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

摘要:

AbstractEs wurden einige bekannte Chinophtalone z. T. auf modifizierte Art hergestellt und IR.‐spektroskopisch mit einer Anzahl neuerer, chinophtalon‐artig gebauter Farbstoffe aus der Reihe der Pyromellitsäure, Naphtalin‐ und Perylen‐tetracarbonsäure v

ISSN:0018-019X    

DOI:10.1002/hlca.19670500804

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

摘要:

AbstractA five‐ or six‐membered ring in pentacyclic azo‐dyestuff‐chromium complexes with the sandwich arrangement, having sulphonamido groups as complex formers, was extended into a nine‐membered ring. This altered not only the electron spectrum but also the stability of the complex. Whilst the five‐ and six‐membered pentacycles are very stable, the corresponding nine‐membered ring complex is considerably less stable. Its stability approaches that of the corresponding 1:2‐Cr complexes which, because of deformed valency angles, are very strained and, therefore, are also very unstable. This tension is counteracted in pentacycles having a lower number of members (5 and 6), and so the system is stabilised. If the number of ring members is increased, this counteraction is reduced and, therefore, the stabilising e

ISSN:0018-019X    

DOI:10.1002/hlca.19670500805

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

摘要:

AbstractThe scintillation quenching effect in a liquid medium (toluene) has been studied for numerous compounds W. The quenching power ξ = d(I0/I)/d[W] of most aliphatic compounds is small, less than 1 1/mole, and may be interpreted by a collision theory. The ketones, and in general all compounds with a high extinction coefficient for toluene fluorescence, have such a high quenching effect that it appears to be due to a transfer by resonance. The experimental data fit the theory perfectly if, in the expression for collisional energy transfer, the average molecular radius is replaced by half the FÖRSTERcritical resonance distance, and if a coefficient of migration of energy is added to the diffusion constant. The transfer is more or less reversible. For compounds which can only be deecxitated by a π‐π* transition, it is completely reversible, and quenching is null. When the excitation energy can be degraded by an‐π* transition, the transfer is completely irreversible, and the quenching is maximum. For intermediate cases, the quenching effect is interpreted with the supplementary hypothesis of an intramolecular energy

ISSN:0018-019X    

DOI:10.1002/hlca.19670500806

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

摘要:

AbstractEPR. investigations show the existence of one‐electron oxidation of 5,6,7,8‐tetrahydropterine and tetrahydrofolic acid resulting in unstable cationic radicals of red color which are trapped at liquid nitrogen temperat

ISSN:0018-019X    

DOI:10.1002/hlca.19670500807

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

摘要:

AbstractThe adducts of acetic, benzoic, cinnamic, and anisic aldehydes with TiCl4have been prepared, and the IR. spectra of the compounds, in the solid state or in solution in CH2Cl2, studied. The lowering of the carbonyl frequency shows that the acceptor is linked by a dative bond to the carbonyl oxygen atom acting as donor.

ISSN:0018-019X    

DOI:10.1002/hlca.19670500808

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

摘要:

AbstractThe isolation and analysis of a cocoa concentrate is described: 62 constituents have been identified, 42 of which for the first time. Most identifications are based upon mass spectrometry combined in many cases with IR. spectrometry, and comparison with reference compounds. A number of minor constituents could not be identified.

ISSN:0018-019X    

DOI:10.1002/hlca.19670500809

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

摘要:

AbstractIt is shown that pyrazoles and indazoles undergo photochemical bond‐switchin

ISSN:0018-019X    

DOI:10.1002/hlca.19670500810

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY

ISSN:0018-019X    

DOI:10.1002/hlca.19670500811

出版商:WILEY‐VCH Verlag GmbH    

年代:1967

数据来源: WILEY