摘要:

AbstractNuclear magnetic resonance has been employed to investigate the structure of the complexes (π‐allyl) PdCl(L) (L = phosphine, Ph3As, Ph3Sb) and the conformational rearrangements of the allyl group in these compounds as affected by the ligand, the ligand‐to‐metal ration and the temperature (in CDCl3).Several types of rearrangement were observed, depending on the choice of the variables mentioned above. At low temperatures a short‐lived σ‐allyl intermediate was found in the case of the phosphines only, whereas at higher temperatures rotation of the π‐allyl group was inferred for all the ligands. At very high temperatures and high ligand‐to‐metal ratios a σ‐allyl group had to be postulated to explain the NMR spectra, which are analogous to those of σ‐allyl‐magnesium halide compounds.A molecular orbital description has been used to rationalize some o

ISSN:0165-0513    

DOI:10.1002/recl.19660851102

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19660851103

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

摘要:

AbstractReactions of 2‐methyl‐, 2‐ethyl‐, 2‐phenyl‐, 2,5‐ and 2,6‐dimethyl‐4‐chloropyrimidine with potassium amide in liquid ammonia have been investigated.Together with aminations leading to the formation of 4‐amino compounds, conversions involving a ring transformation were found to occur. The latter process occurred in aminations of the three first‐mentioned substances, 2,4‐dimethyl‐, 2‐ethyl‐4‐methyl‐ and 4‐methyl‐2‐phenyl‐s‐triazine respectively being formed. Also from 4‐chloro‐2,5‐dimethylpyrimidine as‐triazine derivative, 4‐ethyl‐2‐methyl‐s‐triazine, was obtained. The last‐mentioned reaction indicates that in the ring transformation pyrimidynes are not involved and that the 5‐methyl group and the 5‐carbon atom of the pyrimidine ring contribute to the formation of the ethyl group in the

ISSN:0165-0513    

DOI:10.1002/recl.19660851104

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

摘要:

AbstractBy applyingMcDanielandBrown'smethod2for the separation of polar and steric effects ofo‐alkyl groups toRochester'sdata1for the ionization constants of methylphenols in methanol, theo‐effect of a methyl group was shown to be 0.33 ± 0.01 pK‐units.This figure is much larger than the corresponding figure for theo‐effect in water as the solvent (0.14 ± 0.01), showing that theo‐effect is strongly solvent‐dependent and thus lending further support to the view that it is mainly caused by steric hindrance

ISSN:0165-0513    

DOI:10.1002/recl.19660851105

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

摘要:

AbstractThe development of fluorescent compounds has been studied in mixtures of amines and aldoses undergoing Maillard reaction at moderate temperatures, and the fluorescence emission spectra of someN‐substituted 1‐amino‐1‐deoxy‐2‐ketoses are given. A study of pH‐dependency suggests fluorescence to be mainly due to the 1,2‐enol and 2,3‐enediol tautomers of the Amadori product formed, the latter enol contributing in the form of a cyclic configuration.Some results are presented illustrating the formation of highly resistant nitrogen‐containing ring systems during Kjeldahl‐digestion ofN‐substituted 1

ISSN:0165-0513    

DOI:10.1002/recl.19660851106

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

摘要:

AbstractThe extended Hückel theory applied to single molecules of simple carboxylic acids is able to provide an explanation for the coplanarity of many carboxyl groups with an α‐substituent, which is observed in the crystalline state. Quantitative agreement with experimental rotation barriers is poor, but the shape of the calculated barriers largely agrees with experimental d

ISSN:0165-0513    

DOI:10.1002/recl.19660851107

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

摘要:

AbstractThe addition of bromine chloride, preparedin situfromN‐bromosuccinimide and hydrogen chloride, to a number of alkyl cyclohexenes has been studied. The addition leads to mixtures of isomerictrans‐bromochloroalkylcyclohexanes. A two‐stage mechanism, involving the formation of a cyclic bromonium‐ion intermediate, followed by atrans‐diaxial opening of the cyclic intermediate is proposed to account for the experimenta

ISSN:0165-0513    

DOI:10.1002/recl.19660851108

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

摘要:

AbstractFor reactions of the typeL‐O, generally called “cis‐ligand insertion”, there is increasing experimental evidence that the groupQ migrates. The present paper gives a theoretical analysis of this rearrangement, which is illustrated by the specific example of the growth reaction in Ziegler polymerizations ofa‐olefins:As a first approximation to the reaction path the angular vibrabtion of R is analysed from a quantum‐mechanical point of view, showing the role that d orbitals in transition‐metal compounds play in the migration of alkyl groups to π‐bonded olefins.It appears that the migrating ligands finds a suitable combination of orbitals to remain bonded to the complex all along the rea

ISSN:0165-0513    

DOI:10.1002/recl.19660851109

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19660851110

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19660851111

出版商:WILEY‐VCH Verlag    

年代:1966

数据来源: WILEY