摘要:

AbstractThe17O chemical shifts have been measured for 51 α,β‐unsaturated and aromatic ethers. A good linear relationship is found between the17O chemical shifts in a series of dialkyl and the corresponding alkyl vinyl ethers. Hence, the extent ofp,π‐interaction, between the oxygen atom and the vinyl group in the latter series does not, apparently, depend upon branching at the α‐carbon atom in the alkyl moiety of these ethers. The PhOButether, however, as compared to the other alkyl phenyl ethers, shows significantly weakenedp,π‐interaction, which is apparently related to the steric hindrance of this interaction. The effects of two unsaturated groups upon the17O chemical shifts in the corresponding ethers are non‐additive. This is undoubtedly a result of ‘rivalry’ between these groups for conjugation with the lone electron pairs on the ethereal oxygen. The17O chemical shift ranges of substituted methyl and vinyl phenyl ethers are nearly equal (≈30 ppm). An analysis of the17O shielding for cyclopropyl ethers shows no observablep,σ‐conjugation in these compounds. Excellent correlation (r>0.99) between the values of17O chemical shifts and the calculated (MO LCAO SCF, CNDO/2) π‐electron charges on the corresponding oxygen atoms look promising for experimental estimations of π‐electron den

ISSN:0030-4921    

DOI:10.1002/mrc.1270180102

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe15N chemical shifts and1H15N and13C15N coupling constants of nine monolabelled indazoles were measured and assigned. The experimental values are discussed in terms of the indazolic and iso‐indazolic structures, and compared with literature data for other related heterocycles. All the results are consistent with an N‐1(H) tautomeric structure for indazole in

ISSN:0030-4921    

DOI:10.1002/mrc.1270180103

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe structural analysis of carbamates derived from 2‐(α‐furyl)benzaldoximes and 2‐(α‐furyl)benzyl alcohols was carried out by1H and13C NMR spectroscopy. The conjugative and steric effects of alkyl substituents introduced on the benzene rings were found to modify the relative orientation of the aromatic and furan rings. The existence of a close relationship between the stereochemistry of the studied compounds and their anticholinesterase activity has been

ISSN:0030-4921    

DOI:10.1002/mrc.1270180104

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe proton spectra of phthalonitrile, including13C‐ and15N‐satellites at natural abundance in isotropic and oriented solvents, have been analysed. The entirerα‐structure is derived from the direct couplings. The AISEFT method has been used for obtaining the pure satellite infor

ISSN:0030-4921    

DOI:10.1002/mrc.1270180105

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractA correlation ofparasubstituted13C chemical shifts in aromatic compounds with substituent polar (inductive) and resonance constants σ* and σrof aliphatic compounds has been studied. It has been shown that the precision of the correlations obtained corresponds to that of the Swain‐Lupton and Taft two‐parameter equations, but the correlation equation used in this work seems to permit a more exact separation of the substituent effects of aromatic compounds into inductive and resonance contributions. Thus, σ* and σrsubstituent constants are universal parameters which can be used in a correlation analysis of the properties of both aliphatic and aromatic co

ISSN:0030-4921    

DOI:10.1002/mrc.1270180106

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe high‐resolution proton‐coupled13C NMR spectra of 2‐chloro‐ and 2‐phenyl‐4‐methyl‐1,3,2‐dithiarsolane and 2‐chloro‐ and 2‐phenyl‐1,3,2‐dithiarsolane have been obtained and completely analysed. The spectral analysis has provided all the13C chemical shifts and13C1H coupling constants, including their relative signs. The results of this work are adequately interpreted in terms of two rapidly equilibrating half‐chair conformers with the 4‐methyl pseudo‐axial or pseudo‐equatorial. Thecisisomers appear to be conformationally biased towards the form with the 4‐methyl pseudo‐equatorial. The two one‐bond13C1H coupling constants of the methylene group are distinctly different. For both thecisandtransisomers, the largest one‐bond coupling always involves the methylene proton situatedsynto the substituent at arsenic. The observed variation in the geminal and vicinal13C1H coupling constants are discussed in terms of a stereospecific inductive effect of th

ISSN:0030-4921    

DOI:10.1002/mrc.1270180107

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe1H,13C and77Se chemical shifts have been measured for mononitrobenzo[b]selenophenes. For the homocyclic nuclei, the observed1H‐ and13C‐values calculated from the empirical increments of nitrobenzene. Anomalous effects are observed in the 2‐ and 3‐substituted derivatives and the nature of the SeNO2interactions in the former is discussed.77Se chemical shifts of the 4‐, 5‐ and 7‐nitro derivatives are approximately correlated with the CNDO calculated electron densities; they also compare well with those of selenoanisoles and other phenyl alkyl selenides. The chemical shifts are also compared with the corresponding values in other heterocycles containing a sel

ISSN:0030-4921    

DOI:10.1002/mrc.1270180108

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

Abstract13C NMR shifts oftrans‐ andcis‐annelated bicyclo[4.3.0]nonanes with substituents R in position 8 (R  H, OH, Cl, Br) and 1‐hydroxy derivatives were analysed on the basis of force field calculated torsional angles using Allinger's MM1 program. Shielding increments for the 6 membered ring agree with corresponding cyclohexane values within ± 0.8 ppm maximal deviation.13C NMR line shape analysis withcis‐hydrindane between 148 and 180 K yielded ΔH* = 37.0 ± 0.4 kJ mol−1and ΔS* = 28 J mol−1K−1for the topomerization. The force field calculated reaction profile showed ΔH* = 37 kJ mol

ISSN:0030-4921    

DOI:10.1002/mrc.1270180109

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractFrom analysis and refinement by the LAOCOON III program of the 220 MHz1H spectrum of 2,2′‐biquinoline, recorded as a saturated solution in carbon disulphide, most derived chemical shifts and coupling constants are close to corresponding values in quinoline. However, H‐3 is at 1.5 ppm lower field in 2,2′‐biquinoline than in quinoline and theortho‐coupling3J(34) in the heterocyclic ring is 0.5 Hz larger in 2,2′‐biquinoline than in quinoline; fairly free rotation about the 2,2′

ISSN:0030-4921    

DOI:10.1002/mrc.1270180110

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe nature of the metalloporphyrin‐ligand complexes produced by zinc, magnesium and cobalt porphyrins with basic ligands has been investigated using the diamagnetic ring current shifts of the porphyrin on the ligand protons. The metal to nitrogen bond lengths in some metallo‐meso‐tetraphenylporphyrin (pyridine) complexes have been determined and compared with the data of the crystalline complexes. The geometry of the Znmeso‐tetraphenylporphyrin complexes with 2‐picoline, quinoline and isoquinoline has been investigated. Steric interactions between the ligand and the porphyrin in 2‐picoline and quinoline produce a dramatic increase in the ZnN bond length when compared to the unstrained analogues pyridine and isoquinoline. This large increase is associated with comparatively minor angle distortions in the complex. The specificity of the Znmeso‐tetraphenylporphyrin complexation shifts has been determined for a range of benzyl and butyl compounds. The complexation shift is linearly related to the basicity of the ligand for a wide rang

ISSN:0030-4921    

DOI:10.1002/mrc.1270180111

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY