Concerning the conformational distribution in isopropylcyclopropane

A partial analysis of the 400 MHz 1H nmr spectrum of isopropylcyclopropane yields 8.6 ± 0.2 Hz for the vicinal proton–proton coupling constant between a cyclopropyl proton and the methine proton of the isopropyl group. The fractional population of the s-trans conformer is estimated as 0.65 ± 0.l0 at 300 K, in reasonable agreement with molecular mechanics and INDO MO computations of the energies of the gauche and trans forms.The conformational preference of this molecule is similar to that in n-butane and in vinylcyclopropane but contrasts with that in biisopropyl and bicyclopropyl.

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

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19930173 ◽

1993 ◽

Vol 58 (1) ◽

pp. 173-190 ◽

Cited By ~ 1

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.

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Studies on the PMR Spectra of Oxetanes. VI 2-(3-Chlorophenyl)oxetane and 2-(2-Chlorophenyl)oxetane at 60 and 100 MHz

Zeitschrift für Naturforschung A ◽

10.1515/zna-1974-1229 ◽

1974 ◽

Vol 29 (12) ◽

pp. 1902-1906 ◽

Cited By ~ 2

Author(s):

Jukka Jokisaari

Keyword(s):

Long Range ◽

Chemical Shifts ◽

Methine Proton ◽

Coupling Constants ◽

Coupling Constant ◽

Proton Proton ◽

Temperature Range ◽

Proton Coupling ◽

Phenyl Proton ◽

Pmr Spectra

The 100 MHz spectra of the phenyl protons in 2-(3-chlorophenyl) oxetane and 2-(2-chlorophenyl) oxetane have been analysed. The 60 MHz PMR chemical shifts and proton-proton coupling constants have been studied in the temperature range from -20 C to +80 °C. The chemical shifts were sensitive to temperature, while the coupling constants were not, except the long range 5Jm coupling constant between the methine proton and the meta positioned phenyl proton in 2-(2-chlorophenyl) oxetane.

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ChemInform Abstract: CHOICE OF NUCLEAR MAGNETIC RESONANCE VICINAL PROTON-PROTON AND VICINAL CARBOXYLATE CARBON-13-PROTON COUPLING CONSTANT PARAMETERS FOR ESTIMATING CONFORMATIONS IN AMINO ACIDS

Chemischer Informationsdienst ◽

10.1002/chin.197951057 ◽

1979 ◽

Vol 10 (51) ◽

Author(s):

R. B. MARTIN

Keyword(s):

Amino Acids ◽

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Coupling Constant ◽

Proton Proton ◽

Proton Coupling ◽

Vicinal Proton ◽

Nuclear Magnetic

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Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

Canadian Journal of Chemistry ◽

10.1139/v80-395 ◽

1980 ◽

Vol 58 (23) ◽

pp. 2452-2459 ◽

Cited By ~ 2

Author(s):

Ted Schaefer ◽

Leonard J. Kruczynski ◽

Bert Krawchuk ◽

Rudy Sebastian ◽

James L. Charlton ◽

...

Keyword(s):

Coupling Constants ◽

Molecular Orbital Calculations ◽

Proton Proton ◽

H Nmr ◽

Proton Coupling ◽

Conformational Preferences ◽

Carbon Carbon Bonds ◽

Vicinal Proton ◽

Derivatives Of ◽

Low Energy Conformations

The 1H nmr spectra in solution of 1-R-(3,5-dibromophenyl) ethanes (R = CH3, C2H5, n-C3H7 to n-C6H13, OH, F, Br), of 1-amino-2-(3,5-dichlorophenyl) ethane, of 3,5-dichloroallylbenzene, and of 4-(3,5-dibromobenzyl) pyridine are analyzed at 305 K. For the ethane derivatives, the populations of anti and gauche conformers are derived from the vicinal proton–proton coupling constants. The conformation about the C1—Cα bond in both gauche and anti forms is discussed in terms of long-range couplings to the ring protons and some approximate barriers about this bond are suggested for both conformers. Greater rigidity exists in the gauche than in the anti conformations. In some cases the measurements are compared with extensive molecular orbital calculations, for example, for phenethylamine. The low-energy conformations and the barriers about the C1—Cα bond are deduced for the allyl and pyridyl compounds.

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Solution Conformation of Benzimidazole Nucleosides with the Aid of Model Analogues

Zeitschrift für Naturforschung C ◽

10.1515/znc-1981-1-223 ◽

1981 ◽

Vol 36 (1-2) ◽

pp. 126-134 ◽

Cited By ~ 5

Author(s):

Zygmunt Kazimierczuk ◽

Ryszard Stolarski ◽

Lech Dudycz ◽

David Shugar

Keyword(s):

Chemical Shifts ◽

Coupling Constants ◽

Glycosidic Bond ◽

Benzimidazole Ring ◽

Proton Proton ◽

H Nmr ◽

Proton Coupling ◽

Vicinal Proton ◽

Sugar Ring ◽

Derivatives Of

Abstract The 4,6-dibromo-and 5,7-dibromo-derivatives of 1-β-ᴅ-ribofuranosylbenzimidazole, and the 4,6-dibromo-derivative of 1-α-ᴅ-arabinofuranosylbenzimidazole, have been synthesized by condensation of the trimethylsilylated derivative of 4,6-dibromobenzimidazole with the appropriate protected sugar in the presence of SnCl4. Application of the fusion method led to the β-ribofuranoside of 2-methyl-5,6-dichlorobenzimidazole. Two additional analogues of the biologically active ribofuranoside of 5,6-dichlorobenzimidazole, viz. the 2′,3′-O-isopropylidene and the 5′-chloro-5′-deoxy derivatives have been synthesized. Analyses of the 1H NMR spectra of the foregoing, and of previously synthesized 5(6)-mono-halogeno and 5,6-dihalogeno derivatives, were employed to determine solution conformations of these nucleosides. Conformations of the sugar rings and exocyclic groups were evaluated from vicinal proton-proton coupling constants, as for purine nucleosides. The conformation of the benzimidazole ring about the glycosidic bond was determined from the chemical shifts of the sugar protons, principally H(2′), with the aid of model analogues in fixed syn and anti conformations; and, independently, from the chemical shifts of the benzimidazole ring protons, principally H(4) and H(7). The halogenated benzimidazole ribofuranosides exhibit conformations of the sugar ring similar to those for purine β-nucleosides, but differ from the latter in their preference for the conformation syn about the glycosidic bond.

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Choice of nuclear magnetic resonance vicinal proton-proton and vicinal carboxylate carbon-13-proton coupling constant parameters for estimating conformations in amino acids

The Journal of Physical Chemistry ◽

10.1021/j100481a020 ◽

1979 ◽

Vol 83 (18) ◽

pp. 2404-2407 ◽

Cited By ~ 26

Author(s):

R. Bruce. Martin

Keyword(s):

Amino Acids ◽

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Coupling Constant ◽

Proton Proton ◽

Proton Coupling ◽

Vicinal Proton ◽

Nuclear Magnetic

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

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19882503 ◽

1988 ◽

Vol 53 (11) ◽

pp. 2503-2510 ◽

Cited By ~ 3

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.

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