Fluorine NMR Spectroscopy. V. A Carbon‐13 Study of Coupling Constants between cis and trans CF3 Groups in Highly Fluorinated Olefins

1961 ◽  
Vol 35 (6) ◽  
pp. 2263-2265 ◽  
Author(s):  
George Van Dyke Tiers
Keyword(s):  
Nmr Spectroscopy ◽  
Coupling Constants ◽  
Fluorine Nmr ◽  
Cis And Trans

Geometrical isomerism and 19F NMR spectroscopy of octahedral perfluoroethyl- and perfluoropropyl-substituted β-diketonates and monothio-β-diketonates of rhodium(III)

1999 ◽  
Vol 77 (11) ◽  
pp. 1734-1744 ◽  
Author(s):  
Gary A Stern ◽  
John B Westmore
Keyword(s):  
Nmr Spectroscopy ◽  
Room Temperature ◽  
Chelate Ring ◽  
Coupling Constants ◽  
Octahedral Complex ◽  
Rhodium Complexes ◽  
Octahedral Structure ◽  
Fluorine Nmr ◽  
Geometrical Isomerism ◽  
Geminal Coupling

In solution in acetone at room temperature, tris(perfluoropropanoyl and perfluorobutanoyl)benzoylmethanate complexes of rhodium(III) are shown by 19F NMR spectroscopy to exist as nearly statistical 1:3 mixtures of their respective fac and mer octahedral isomers, whereas the analogous perfluoroalkanoylthiobenzoylmethanate complexes have a fac-octahedral structure. For all four complexes studied, vicinal F-F coupling constants are too small (0-3 Hz) to lead to resolved multiplet peaks, so that perfluoroethyl groups show singlet resonances for their CF3 groups. Since four-bond coupling constants are significantly larger, ~9 Hz, perfluoropropyl groups show the expected multiplet resonances for their CF3 groups. In acetone, AB patterns, with geminal coupling constants equal to approx. 270 Hz, are observed for the CF2 groups next to the chelate ring (except for the perfluoropropanoylthiobenzoylmethanate complex). (These observations are modified by solvent. In toluene, one of the AB patterns of a mer-octahedral complex collapses to a single peak.) The AB spectra, which are subject to substituent and solvent effects, can be interpreted in terms of perfluoroalkyl groups rotating rapidly about the Cring-Calkyl bond, with an unsymmetric double potential well, giving unequal rotamer populations. Changes in the spectra were not noticeable over the temperature range accessible in the acetone and toluene solvents used.Key words: rotation, perfluoroalkyl groups, fluorine NMR spectra, fluorine-fluorine coupling constants, fluorinatedβ-diketonate complexes, monothio-beta-diketonates, rhodium complexes.

Structural studies of digitoxin and related cardenolides by two-dimensional NMR

1990 ◽  
Vol 68 (2) ◽  
pp. 272-277 ◽  
Author(s):  
Torbjörn Drakenberg ◽  
Peter Brodelius ◽  
Deane D. McIntyre ◽  
Hans J Vogel
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chair Conformation ◽  
Coupling Constants ◽  
Two Dimensional ◽  
Structural Studies ◽  
Solution Conformation ◽  
Phase Sensitive ◽  
Multiple Relay ◽  
C Nmr

The 1H and 13C NMR spectra of the cardenolides digitoxigenin, digoxigenin, digitoxin, and mono- and bis-digitoxigenin digitoxosides have been completely assigned by two-dimensional NMR spectroscopy. The techniques used include phase-sensitive COSY, multiple relay COSY, and carbon–proton correlation (HETCOR and HMQC) spectra. Various aspects of the solution conformation of the steroid moiety of digitoxin and digoxigenin could be determined from coupling constants and NOE difference experiments and they are indicative of an all-chair conformation. The carbohydrate rings in digitoxin and the mono- and bis-digitoxigenin digitoxosides are also in the chair conformation. Keywords: cardenolides, digitoxigenin, digitoxin, 2-dimensional NMR, conformational analysis.

Nuclear magnetic resonance studies on the anions [M(SnCl3)5Cl]4− (M = Ru, Os) and [Ru(SnCl3)5(MeCN)]3−: the X-ray crystal structure of [N(C2H5)4]4[Ru(SnCl3)5Cl]

1982 ◽  
Vol 60 (11) ◽  
pp. 1304-1316 ◽  
Author(s):  
Louis J. Farrugia ◽  
Brian R. James ◽  
Claude R. Lassigne ◽  
Edward J. Wells
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Octahedral Geometry ◽  
Coupling Constants ◽  
Order Effects ◽  
Magnetic Resonance Studies ◽  
X Ray ◽  
Crystallographic Study

The octahedral anions [M(SnCl3)5Cl]4− (M = Ru, Os) have been fully characterized by 119Sn FT nmr spectroscopy. For M = Ru, 117Sn and 115Sn nmr spectra were also recorded, and an X-ray crystallographic study was carried out on the tetraethylammonium salt, isolated as a disolvate from acetonitrile. The Ru—Sn bond lengths indicate some degree of dπ–dπ interactions. The slight distortions from octahedral geometry are discussed in connection with the packing of the chlorine atoms. The Sn nmr spectra reveal the first observed coupling to a 99Ru nucleus (I = 5/2, 12.7% natural abundance), very large 2J(119Sn—117Sn) coupling constants, and the first observed second-order effects on a heteronuclear system. The octahedral anion [Ru(SnCl3)5(MeCN)]3− was also synthesized as the tetraethylammonium salt and characterized spectroscopically.

"Through-space" spin–spin coupling between thallium and fluorine in fluorophenylthallium compounds

1989 ◽  
Vol 67 (11) ◽  
pp. 1847-1850
Author(s):  
Gerald Norman Pecksen ◽  
Raymond Frederick Martin White
Keyword(s):  
Coupling Constants ◽  
Spin Coupling ◽  
Methyl Group ◽  
Fluorine Nmr ◽  
Thallium Atom ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Thallium to fluorine spin–spin coupling constants have been measured for a number of fluoro- and trifluoro-methyl-substituted mono- and di-arylthallium derivatives. The results provide evidence of "through-space" coupling in the diaryl derivatives when the fluoro- or trifluoro-methyl group is ortho to the thallium atom. Keywords: thallium, fluorine, NMR, through-space coupling.

scholarly journals IDENTIFICATION AND SEQUENCING BY NMR SPECTROSCOPY OF THE CARBOHYDRATE MOIETY IN A SAPONIN FROM Barringtonia asiatica

2010 ◽  
Vol 1 (3) ◽  
pp. 120-124
Author(s):  
Rymond J Rumampuk
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Coupling Constants ◽  
Carbohydrate Moiety ◽  
Glycosidic Linkage ◽  
1H And 13C Nmr ◽  
Heteronuclear Correlation ◽  
Vicinal Coupling Constants ◽  
Nmr Signals

A trisaccharide chain in a saponin from the seeds of Barringtonia asiatica has been identified and sequenced as {[b-D-galactopyranosyl(1®3)- b-D-glucopyranosyl(1®2)]-b-D-glucuronopyranosyloxy} using a combination of homonuclear and heteronuclear correlation NMR spectroscopy. The 1H and 13C NMR signals of the sugar residues can be determined and distinguished from one other by use of the HMQC-TOCSY technique. Anomeric configurations were unambiguously assigned from the vicinal coupling constants 3JH-1,H-2 of the anomeric protons. Inter-glycosidic linkage assignments were elucidated using  HMBC.   Keyword: Barringtonia asiatica, carbohydrate, saponin, NMR

In-plane and out-of-plane conformational preferences of the sulfhydryl group in some halothiophenol derivatives

1979 ◽  
Vol 57 (12) ◽  
pp. 1421-1425 ◽  
Author(s):  
Ted Schaefer ◽  
William J. E. Parr
Keyword(s):  
Sulfhydryl Group ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Group ◽  
Recent Analysis ◽  
Phenol Derivatives ◽  
Out Of Plane ◽  
Intramolecular Hydrogen ◽  
Cis And Trans ◽  
Spin Spin Coupling

Long-range spin–spin coupling constants between sulfhydryl protons and ring protons in some halothiophenol derivatives in CCl4 solutions are reported. In contrast to the corresponding phenol derivatives, substantial amounts of out-of-plane conformers are present at 305 K for all but 2,6-dichlorothiophenol. The cis and trans conformers differ by only about 0.2 kcal/mol in free energy for 2,4-dibromothiophenol and 2,4-dichlorothiophenol, in good agreement with a recent analysis of the dipole moment observed for the latter compound. The barrier to internal rotation of the sulfhydryl group is considerably smaller than for a hydroxyl group and rough estimates are given for the barrier in a few compounds. For example, the barrier in 2,3,5,6-tetrafluorothiophenol is lower than in 2,6-dichlorothiophenol. STO-3G MO calculations overestimate the internal barrier to rotation of the sulfhydryl group, but yield charge densities for this group which indicate that a major cause of the relative weakness of its intramolecular hydrogen bonds resides in its lack of polarity.

Hexaethyl-2,4-dicarba-nido-hexaborane(8), Deprotonation and Complexation Studied by NMR Spectroscopy and Density Functional Theory (DFT) Calculations

2004 ◽  
Vol 59 (6) ◽  
pp. 685-691 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Hans-Jörg Schanz
Keyword(s):  
Density Functional Theory ◽  
Nmr Spectroscopy ◽  
Density Functional ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Analogous Reaction ◽  
Sandwich Complex ◽  
Dft Methods ◽  
Functional Theory ◽  
Nmr Data

Deprotonation of hexaethyl-2,4-dicarba-nido-borane(8) 2 leads first to the hexaethyl-2,4-dicarbanido- borate(1−) 3, and further deprotonation, using BuLi/KOtBu, gives the hexaethyl-2,4-dicarbanido- hexaborate(2−) 4. The reaction of 3 with FeCl2 affords the commo-ferracarborane [Fe(Et6-2,4- C2B4H)2] 5, and the analogous reaction of 4 leads to the anionic sandwich complex [Fe(Et6-2,4- C2B4)2]2− 6 which can be protonated to give 5. The complex 5 contains two hydrido ligands, each bridging the iron and two boron atoms. Reactions were monitored and the products were characterised by 11B NMR spectroscopy in solution. The geometries of the carboranes, the borates (all unsubstituted and permethyl-substituted) and the iron complexes (all unsubstituted) were optimised by DFT methods [B3LYP/6-311+G(d,p) or B3LYP/6-31+G(d)], and the relevant NMR data [chemical shifts δ11B, δ13C, δ57Fe, and coupling constants 1J(13C,1H), 1J(11B,1H), 1J(57Fe,1H), 1J(57Fe,11B)] were calculated at the same level of theory.

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