摘要:

AbstractESR and optical absorption studies have been carried out on bis[N‐(2‐hydroxyethyl)ethylenediamine] copper II‐chloride, ‐bromide, ‐nitrate, ‐sulphate, bis(N‐methylethylenediamine) copper II thiocyanate and bis(N,N′‐dimethylethylenediamine) copper II thiocyanate, in non‐interacting solvents at room and liquid nitrogen temperatures. The molecular orbital coefficients are estimated assuming axial symmetry and indicate that the in‐plane π bond is as strong as the σ bond. The consistency in the value of the χ parameter, which is proportional to the hyperfine constants, indicates that it is quite independent of the ligand substitution and depends upon the immediate environm

ISSN:0030-4921    

DOI:10.1002/mrc.1270170402

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

AbstractA series of 6‐X‐3,8‐dioxatricyclo[3.2.1.02,4]octanes (XCO2CH3, CN, Cl and CN) are studied by NMR, after their syntheses by epoxidation of the corresponding 7‐oxabicyclo[2.2.1]heptenes. The NMR parameters (J, δ) are determined, and also the anisotropy effects of methyl groups at the 1,5 bridgehead positions. The results allow an unambiguous identification of the diastereo‐isomers having agem‐chlorocyano group in

ISSN:0030-4921    

DOI:10.1002/mrc.1270170403

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

AbstractA series of 2‐ and 4‐quinolones substituted in the hetero‐ring have been evaluated using13C NMR techniques. Substituent effects are discussed as an aid to evaluation of potential tautomerization in the 2‐quinolone systems. The observed substituent shifts for systems having a hydroxy function at the 4‐position in the 2‐quinolones can be explained without implementing the tautomerism to a

ISSN:0030-4921    

DOI:10.1002/mrc.1270170404

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

AbstractThe13C NMR chemical shifts for 1,3‐dithiolane and 13 methyl substituted derivatives are reported. Substituent effects are derived and compared with those for cyclopentanes and 1,3‐dioxolanes. The magnitude and variety of the substituent effects are best explained with the aid of a half‐chair conformation where the S‐1C‐2S‐3 plane passes betw

ISSN:0030-4921    

DOI:10.1002/mrc.1270170405

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

AbstractThe natural abundance13C NMR spectra of 2,2′‐dimethyl‐, 2,2′‐dimethoxy‐ and 2,2′‐dihydroxybiphenyls, and a series of 2,2′‐dimethoxy‐5,5′‐disubstituted biphenyls were recorded. Unambiguous signal assignments of the carbonsorthoandparato an aryl ring in biphenyls were made by selective deuteration and/or the graphical method for1H single frequency off‐resonance decoupled spectra. Contrary to the reported assignments, it was shown that the signal for C‐6 in 2,2′‐dimethylbiphenyl clearly appears at lower field than that for C‐4. The signals for theorthocarbons (C‐6) of 2,2′‐dimethoxy‐5,5′‐disubstituted biphenyls generally appeared at lower fields than those for theparacarbons (C‐4). The validity of applying deuterium isotope shifts to the assignments of13C chemical shifts of di

ISSN:0030-4921    

DOI:10.1002/mrc.1270170406

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

AbstractThe proton NMR spectrum of azulene has been investigated in the nematic phase of a liquid crystal. Spectral analysis provided the direct dipole‐dipole coupling constants which were used to derive the structural information. It was found that the relative proton‐proton distances in the 7‐ and 5‐membered rings deviate significantly from those for regular heptagons and pentagons. Indirect spin‐spin couplings were also obtained. Many of the inter‐ring and long‐range couplings have magnitudes betwe

ISSN:0030-4921    

DOI:10.1002/mrc.1270170407

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

Abstracttrans‐2‐Alkylaminocyclohexanols andtrans‐2‐alkylaminocycloheptanols condense with formaldehyde to give perhydrocycloalkano[d][1,3]oxazoles, whereastrans‐2‐alkylaminocyclopentanols give rise to perhydrocyclopentano[f][1,3,5]dioxazepines. The two types of ring systems are characterized by differing proton‐proton geminal coupling constants and13C N

ISSN:0030-4921    

DOI:10.1002/mrc.1270170408

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

AbstractThe γ effects on13C shielding have been examined for a series of rigid molecules containing the substituents CH3, OH, NH2, F, Cl, Br or I. Plots of the γ effect vs the CC‐αC‐βX dihedral angle are well scattered if the plots do not distinguish modes of substitution. For the series in which the resonating carbon is CH2, however, fairly linear correlations are observed for XCH3, OH, NH2, Cl and Br. It is concluded that within a structurally defined and substitutionally homogeneous series, there is a reasonably linear stereochemical dependence. Although substitution at C‐α does not seriously alter the linear relationship, hybridization of the intermediate carbons may be important. The slopes of the plots for the γ effect vs dihedral angle are remarkably similar. Neither a strictly steric (van der Waals) nor a strictly polar source can be the cause of the linear relationship, since our series of substituents ranges widely with respect to both size and electronegativity. The only two factors that are constant within the series are the removal of the hydrogen atom (CCCH to CCCX) and the addition of the bonding and nonbonding orbitals

ISSN:0030-4921    

DOI:10.1002/mrc.1270170409

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

AbstractThree γ effects on13C shielding in 3,3‐dimethylheteracyclohexanes as a function of the hetero‐atom X have been examined. The γ‐antieffect on the equatorial 3‐methyl group is small in absolute magnitude but strongly dependent on the polar properties of X. The plot of the13C shielding of this carbon vs the electronegativity of X is linear, with a slope of −5.8 ppm/electronegativity unit. The γ‐gaucheeffects on the axial 3‐methyl group and on the 4‐carbon are large in absolute magnitude but have quite different dependences on the polar properties of X. Whereas the shielding of the 4‐carbon exhibits a linear dependence on electronegativity (slope −3.5), the axial 3‐methyl group shows little dependence (slope crudely −0.7), even though the geometric relationship between X and either carbon is almost the same. Neithergauchecarbon shielding appears to be related to the steric properties of X. The polar component of both the γ‐antieffect and the γ‐gaucheeffect is interpreted as arising from overlap of appropriately positioned parallel orbitals. For theanticase, the pathway is the familiar zigzag arrangement of bonds. For thegauchecase, the pathway may be either through space (the orbitals would be only on X and C‐α; for the 4‐carbon, this interaction would be through the center of the ring) or through bonds (there are parallel axial orbitals on all four atoms). The absence of a significant polar effect for the axial 3‐methyl group suggests that thegaucheinteraction requires a rigid pathway. The polar component of the general γ‐gaucheeffect is superimposed upon a larger contribution that is essentially independent of the nature of X and may be associated with the removal of the hydrogen on the

ISSN:0030-4921    

DOI:10.1002/mrc.1270170410

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY

摘要:

AbstractThe13C NMR data of imidazole, andN‐methyl‐,N‐acetyl‐,N‐trifluoroacetyl‐,N‐heptafluorobutyryl‐ and 2‐methyl‐imidazoles, were obtained from proton‐noise decoupled and single frequency NOE13C NMR spectra. The considerable changes in the directly‐bonded (C, H) coupling constants uponN‐acetylation of the imidazole ring, which are comparable to those noted when going from the neutral to the cationic form of imidazole, are primarily due to the large π‐electron transfer ability of theN‐acetyl‐ andN‐trifluoroacetyl‐substituents. The differences in magnitude of the three‐bond (C, H) coupling constants along different paths in the imidazole ring may be attributed to the larger π‐contributions across a pyridine‐like

ISSN:0030-4921    

DOI:10.1002/mrc.1270170411

出版商:John Wiley&Sons Limited    

年代:1981

数据来源: WILEY