Transoid Homoallylic Proton-Proton Coupling Constants

1989 ◽  
Vol 42 (5) ◽  
pp. 659 ◽  
Author(s):  
M Barfield ◽  
RJ Spear ◽  
S Sternhell
Keyword(s):  
Angular Dependence ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Mo Calculations ◽  
Proton Proton ◽  
Proton Coupling ◽  
Tentative Assignment ◽  
Single Compound ◽  
Derivatives Of

Transoid homoallylic coupling constants (5JH,H) for six compounds (5,10-dihydroindeno[2,1-alindene and confertifolin derivatives) of fixed stereochemistry were determined and compared with calculated values. Magnetic equivalence limited discrete determination of 5Jtrans and 5Jcis to three of these compounds. The single compound where unequivocal assignment could be made revealed 5Jtrans > 5Jcis; this was supported in two other compounds by tentative assignment. Changes in the magnitude of the couplings suggested that substantial substituent effects may be operative. INDO-MO calculations correctly predicted the angular dependence but incorrectly predicted 5Jcis > 5Jtrans.

21,22-Disubstituted 18α,19βH-Ursane Derivatives with Oxabicyclooctane System in Ring E

1993 ◽  
Vol 58 (1) ◽  
pp. 173-190 ◽  
Author(s):  
Eva Klinotová ◽  
Jiří Klinot ◽  
Václav Křeček ◽  
Miloš Buděšínský ◽  
Bohumil Máca
Keyword(s):  
Spectral Data ◽  
Spin Systems ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Nmr Spectrum ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
C Nmr

Reaction of 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) and 20β,28-epoxy-21,22-dioxo-19α,19βH-ursan-3β-yl acetate (IIIb) with diazomethane afforded derivatives XII-XIV with spiroepoxide group in position 21 or 22, which were further converted into hydroxy derivatives XV and XVII. Ethylene ketals VIII-X were also prepared. In connection with the determination of position and configuration of the functional groups at C(21) and C(22), the 1H and 13C NMR spectral data of the prepared compounds are discussed. Complete analysis of two four-spin systems in the 1H NMR spectrum of bisethylenedioxy derivative Xb led to the proton-proton coupling constants from which the structure with two 1,4-dioxane rings condensed with ring E, and their conformation, was derived.

Substituent effects on geminal proton–proton coupling constants

1970 ◽  
Vol 48 (13) ◽  
pp. 2134-2138 ◽  
Author(s):  
Y. L. Chow ◽  
S. Black ◽  
J. E. Blier ◽  
M. M. Tracey
Keyword(s):  
Carbon Tetrachloride ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Geminal Coupling ◽  
Hammett Σ Constants

The geminal coupling constants between the non-equivalent benzylic protons of a series of para- and meta-substituted N-benzyl-2-methylpiperidines were shown to be proportional to the Hammett σ constants of the substituents with ρ −1.38 in carbon tetrachloride, −1.21 in benzene, and nearly 0 in 1 N DCl solutions. The ρ values were compared with those of other series and were discussed in terms of the possible conformations involved. The chemical shifts of the benzylic protons of the piperidine derivatives did not give a good correlation with the Hammett σ constants in these solvents.

The Molecular Structure of Allenes and Ketenes, XII [1] Four-Bond Proton-Proton Spin-Spin Couplings in Allenes

1978 ◽  
Vol 33 (8) ◽  
pp. 932-936 ◽  
Author(s):  
Wolfgang Runge
Keyword(s):  
Molecular Structure ◽  
Charge Transfer ◽  
Quantum Chemical ◽  
Substituent Effects ◽  
Proton Spin ◽  
Coupling Constants ◽  
Proton Proton ◽  
Resonance Effects ◽  
Proton Coupling ◽  
Parameter Approach

Abstract Four-bond proton-proton coupling constants in allenes are reported. The substituent effects on the coupling constants are discussed on the basis of the dual-substituent parameter approach. Furthermore, the coupling constants are related to quantum-chemical indices (electron densities, overlap populations) obtained from semiempirical CNDO/S and ab initio STO-3G calculations.The magnitudes of the coupling constants depend upon the polar natures of the substituents as well as upon their charge-transfer abilities (resonance effects) to a com-parable amount.In general, the coupling constants in 1,3-disubstituted allenes are nonadditive in ligand -specific parameters.

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