Determination of proton-proton coupling constants in 13C-labeled molecules

1992 ◽  
Vol 97 (2) ◽  
pp. 426-434 ◽  
Author(s):  
C Griesinger ◽  
U Eggenberger
Keyword(s):  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling

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.

Concerning the extension of the J method for internal barriers to six-bond couplings to 19F in the 4-fluorophenyl fragment

1978 ◽  
Vol 56 (18) ◽  
pp. 2442-2446 ◽  
Author(s):  
Ted Schaefer ◽  
Werner Danchura ◽  
Walter Niemczura ◽  
James Peeling
Keyword(s):  
Ground State ◽  
Proton Magnetic Resonance ◽  
Coupling Constants ◽  
Side Chain ◽  
Fluorine Nucleus ◽  
Proton Proton ◽  
Proton Coupling ◽  
Carbon Carbon Bond ◽  
Internal Barriers

The long-range coupling constants over six bonds from the side-chain protons to the fluorine nucleus on the ring are extracted from the proton magnetic resonance spectra of p-fluorobenzyl cyanide, chloride, and bromide; of p-fluorobenzal chloride; and of p-fluoroisopropylbenzene. On the assumption that these couplings are transmitted via a σ–π mechanism, a hindered rotor treatment yields the barriers to internal rotation about the carbon–carbon bond which attaches the substituent to the benzene ring. These barriers, when compared to those derived from the analogous proton–proton coupling constants, apparently are accurate enough for the determination of ground state conformations and for a rough assessment of the energetics of conformational interconversions.

2 J HH -resolved HSQC: Exclusive determination of geminal proton-proton coupling constants

2017 ◽  
Vol 282 ◽  
pp. 18-26 ◽  
Author(s):  
Núria Marcó ◽  
Pau Nolis ◽  
Roberto R. Gil ◽  
Teodor Parella
Keyword(s):  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton

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.

Proton magnetic resonance study of the conformation of the pyrrolidine ring in some proline-thiohydantoins

1988 ◽  
Vol 53 (11) ◽  
pp. 2503-2510 ◽  
Author(s):  
Jef J. M. Sleeckx ◽  
Marc J. O. Anteunis ◽  
Frans A. M. Borremans
Keyword(s):  
Present Model ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Proton Magnetic Resonance Study ◽  
Vicinal Proton ◽  
Different Temperatures ◽  
Experimental Justification ◽  
State Assumption ◽  
Methyl Phenyl

The conformational behaviour of a series of N-substituted thiohydantoins of proline was studied by proton NMR. The pseudorotational parameters of the proline moiety were calculated from the ten vicinal proton-proton coupling constants assuming a two state equilibrium (N ⇋ S). The effect of the different substituents (methyl, phenyl, para-nitrophenyl) at the thiohydantoin nitrogen on the conformation of the pyrrolidine rings is discussed. The spectra of proline-N-methylthiohydantoin were recorded at different temperatures in octadeuterotoluene solution. The conformational analysis of these spectra showed that the ratio of the populations of the N and S forms changes considerably with temperature, while the conformational identity of both the N and S forms remains strictly preserved. These facts provide an additional experimental justification of the two-state assumption, at least so for the present model compounds.

Vicinal proton—proton coupling constants. Basis set dependence in SCF ab initio calculations

1993 ◽  
Vol 206 (1-4) ◽  
pp. 253-259 ◽  
Author(s):  
Jesús San-Fabián ◽  
Joaquín Guilleme ◽  
Ernesto Díez ◽  
Paolo Lazzeretti ◽  
Massimo Malagoli ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Coupling Constants ◽  
Basis Set ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton
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