19F coupling constants and chemical shifts in some dimethylamino and alkoxy derivatives of tellurium hexafluoride,cis TeF4XY

1976 ◽  
Vol 8 (10) ◽  
pp. 522-524 ◽  
Author(s):  
John Dalton ◽  
William McFarlane ◽  
Clive R. Wickens ◽  
George W. Fraser ◽  
James B. Millar
Keyword(s):  
Chemical Shifts ◽  
Coupling Constants ◽  
Derivatives Of

15N NMR study of amino-imino tautomerism in derivatives of 1,4-bis(substituted amino)-9,10-anthraquinones and 1,4-bis(substituted amino)-2,3-dihydro-9,10-anthraquinones

1987 ◽  
Vol 52 (3) ◽  
pp. 736-741 ◽  
Author(s):  
Antonín Lyčka ◽  
Libuše Havlíčková ◽  
Alois Koloničný ◽  
Josef Jirman
Keyword(s):  
Chemical Shifts ◽  
Coupling Constants ◽  
15N Nmr ◽  
Nmr Study ◽  
Derivatives Of ◽  
Tautomeric Mixture

The 15N chemical shifts and 1J(15N, H) coupling constants of 1,4-bis(substituted amino)-9,10-anthraquinones and 1,4-bis(substituted amino)-2,3-dihydro-9,10-anthraquinones indicate that these derivatives exist as true aminoderivatives except for 1,4-bis(phenylamino)-2,3-dihydro-9,10-anthraquinone which forms a tautomeric mixture of the amino and imino forms in deuteriochloroform and hexadeuteriodimethyl sulphoxide.

Magnetic non-equivalence of fluorine atoms of a trifluoromethyl group

1982 ◽  
Vol 60 (19) ◽  
pp. 2451-2455 ◽  
Author(s):  
Mohsin A. Khan ◽  
Donald F. Tavares ◽  
Arvi Rauk
Keyword(s):  
Methoxy Group ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Trifluoromethyl Group ◽  
Single Bond ◽  
Hindered Rotation ◽  
Geminal Coupling ◽  
Coupling Pattern ◽  
Derivatives Of

The three fluorine atoms of N,N-dialkyl amide and chloride derivatives of 2-methoxy-2-phenyl-3,3,3-trifluoropropanoic acid are magnetically nonequivalent below –60 °C and exhibit a clear ABC coupling pattern from which chemical shifts and geminal coupling constants are readily derived. The chemical shifts span a range of about 10 ppm and the geminal coupling constants average about 110 Hz. A five bond coupling of about 5 Hz is observed between the hydrogens of the methoxy group and one of the nonequivalent fluorine atoms of the trifluoromethyl group. Barriers to the hindered rotation about the single bond to the trifluoromethyl group are in the range 36–46 kJ/mol.

CYCLOHEXANE COMPOUNDS: IV. NUCLEAR MAGNETIC RESONANCE SPECTRA OF SOME DERIVATIVES OF THE STEREOISOMERIC 3-AMINO-1,2-CYCLOHEXANEDIOLS

1963 ◽  
Vol 41 (9) ◽  
pp. 2331-2338 ◽  
Author(s):  
F. A. L. Anet ◽  
R. A. B. Bannard ◽  
L. D. Hall
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Room Temperature ◽  
Conformational Equilibrium ◽  
Chemical Shifts ◽  
Chloroform Solution ◽  
Coupling Constants ◽  
Order Analysis ◽  
First Order ◽  
Nuclear Magnetic Resonance Spectra ◽  
Derivatives Of

The n.m.r. spectra of 1α-methoxy-2β-hydroxy-3α-aminocyclohexane, 1α-methoxy-2α-hydroxy-3β-aminocyclohexane, their N-acetyl and O,N-diacetyl derivatives, ethoxy analogues, and 3α-amino-1α,2β-cyclohexanediol and 3β-amino-1α,2β-cyclohexanediol triacetates were measured in chloroform solution. From the chemical shifts of the O- and/or N-acetyl methyl protons it was possible to assign conformations to all the substituted derivatives and in most cases the assignments thus made were confirmed by first-order analysis of the multiplet pattern from the methine protons. In all cases, the conformations found were those predicted on simple conformational grounds and no evidence for a conformational equilibrium at room temperature was obtained from the coupling constants. In general, the coupling constants for the methine protons followed the pattern predicted by the Karplus equation. Acetylation of the 1α-alkoxy-2α-hydroxy-3β-aminocyclohexanes with acetic anhydride gave both the O,N-diacetyl derivative and the O,N,N-triacetyl derivative.

CYCLOHEXANE COMPOUNDS: VI. NUCLEAR MAGNETIC RESONANCE SPECTRA OF SOME DERIVATIVES OF THE STEREOISOMERIC 3-BROMO-1,2-CYCLOHEXANEDIOLS AND THE 2-BROMO-1,3-CYCLOHEXANEDIOLS

1966 ◽  
Vol 44 (7) ◽  
pp. 775-780 ◽  
Author(s):  
R. A. B. Bannard
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Angular Distortion ◽  
Order Analysis ◽  
First Order ◽  
Nuclear Magnetic Resonance Spectra ◽  
Derivatives Of ◽  
Magnetic Resonance Spectra

First-order analysis of the 60 Mc.p.s. proton magnetic resonance spectra of 1α-methoxy-2β-acetoxy-3α-bromocyclohexane, 1α-methoxy-2α-acetoxy-3β-bromocyclohexane, 1α-methoxy-2β-bromo-3α-acetoxycyclohexane, 1α-methoxy-2α-bromo-3β-acetoxycyclohexane, and the corresponding diol diacetates confirmed the stereochemical interrelationships of substituents which were assigned previously on chemical grounds, and demonstrated that the compounds exist in chair conformations. The chemical shifts of the methoxy methyl and acetoxy methyl protons did not provide reliable criteria for the assignment of conformations to these substituents in this series. The coupling constants of the methine protons followed, in general, the pattern predicted by the Karplus equation, and the smaller J2,3 values observed in the cis,trans compounds relative to those in the trans,trans compounds are interpreted mainly on the basis of conformational equilibration, upon which is superimposed a small dihedral angular distortion or a remote substituent orientational effect.

THE CONFORMATIONS IN SOLUTION OF trans-CYCLOHEXENE DIHALIDES AND cis- AND trans-1,2-CYCLOHEXANEDIOLS AND DERIVATIVES

1964 ◽  
Vol 42 (4) ◽  
pp. 893-910 ◽  
Author(s):  
R. U. Lemieux ◽  
J. W. Lown
Keyword(s):  
Chemical Shifts ◽  
Coupling Constants ◽  
Spectral Parameters ◽  
Conformational Equilibria ◽  
Karplus Relationship ◽  
In Trans ◽  
Cis And Trans ◽  
Isopropylidene Derivatives ◽  
Derivatives Of

trans-1,4,4-Trideuteriocyclohexene dichloride, dibromide, and diiodide and the 1,4,4-trideuterio-cis- and trans-1,2-cyclohexanediols together with their O-acetyl, O-tosyl, and O-isopropylidene derivatives were synthesized. Their nuclear magnetic resonance (NMR) spectral parameters were obtained with a spectrometer operating at 100 Mc.p.s. and employing double irradiation to establish the chemical shifts and the signs of the coupling constants. The interpretation of the data according to expectations based on the Karplus relationship, for dihedral angles and coupling constants, support the conformational equilibria assigned to the trans-dichloride and trans-dibromide of cyclohexene on the basis of dipole moment measurements (previously published results). The results indicate that trans-cyclohexene diiodide exists to about 84% in the diaxial conformation. In the case of the 1,2-cis-disubstituted cyclohexanes, the occurrence of the signal for the 3-hydrogen in trans relation to the 2-hydrogen at lower field than its geminal 3-hydrogen is assigned to the deshielding influence on the 3-hydrogen when in axial orientation by an opposing axial oxygen at the 1-position. Support for this contention was obtained by determination of the chemical shifts of the geminal hydrogens at the 3- and 5-positions of the cis- and trans-4-t-butyl-2,2,6,6-tetradeuterio-1-methylcyclohexanols. The conformational equilibria indicated for the 1,2-diol, 1,2-diacetoxy, and 1,2-ditosyloxy trans derivatives of 1,4,4-trideuteriocyclohexane by NMR parameters obtained from the spectrum of the O-isopropylidene derivatives of the trans-diol allowed conclusions regarding the non-bonded interaction energies involved. The Karplus relation had to be adjusted to the form, [Formula: see text] and [Formula: see text] to accommodate the results. Solvent effects on conformation are noted. Also, the investigation provided further evidence for the opposite signs of the coupling constants for geminal and vicinal hydrogens. A consideration of the chemical shifts observed for a variety of derivatives of cyclohexanol appears to indicate that intramolecular shielding effects are better accounted for on the basis of neighboring atomic groupings than on the basis of individual chemical bonds.

Pertrimethylsilylation as a method for improvement of chemical shift additivity through conformational homogenization. 1H and 13C NMR spectra of pertrimethylsilylated derivatives of methyl β-D-xylopyranosides

1983 ◽  
Vol 48 (7) ◽  
pp. 1829-1841 ◽  
Author(s):  
Jan Schraml ◽  
Eva Petráková ◽  
Otomar Pihar ◽  
Ján Hirsch ◽  
Václav Chvalovský
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Population Analysis ◽  
Coupling Constants ◽  
Proton Proton ◽  
1H And 13C Nmr ◽  
Proton Coupling ◽  
Derivatives Of ◽  
C Nmr

All possible mono-, di-, and tri- O-methyl, O-benzyl, O-benzoyl, and O-acetyl derivatives of methyl β-D-xylopyranoside were fully trimethylsilylated and their 1H and 13C NMR spectra measured in deuteriochloroform solutions. The spectra were analysed and the chemical shifts completely assigned on the basis of decoupling experiments. The proton-proton coupling constants vary only very little throughout the series. Conformer population analysis by the method of average coupling constants shows that trimethylsilylation increases the C1 conformer population and makes the series conformationally homogenous. Owing to this conformational homogeneity chemical shifts (both 1H and 13C) satisfy very well direct additivity rule. It is suggested that pertrimethylsilylation should be employed whenever deviations from chemical shift additivity are caused by conformational mobility of the investigated series of compounds and when bulky groups can stabilize one of the conformers.

Derivatives of 1-Phenylphthalan, 2-Methyl-1-phenylisoindoline, and 5H-Dibenzo[a,d]cycloheptene Oxides; Synthesis and Conformational Aspects

1971 ◽  
Vol 49 (5) ◽  
pp. 746-754 ◽  
Author(s):  
Robert R. Fraser ◽  
Roger N. Renaud
Keyword(s):  
Chemical Shifts ◽  
Coupling Constants ◽  
Ring Systems ◽  
Geometrical Properties ◽  
Geminal Coupling ◽  
Derivatives Of ◽  
Substituted 1

For the purpose of correlation of chemical shifts and geminal coupling constants with stereochemistry a number of compounds of fixed geometry have been synthesized. These include seven 6-substituted 1-phenylphthalans, five 6-substituted 2-methyl-1-phenylisoindolines, and six 2-substituted 5H-dibenzo-[a,d]cycloheptene oxides. The geometrical properties of the three ring systems are discussed and arguments in favor of a quasi-equatorial epoxide substituent in the latter series are supported by n.O.e. measurements.

Solution Conformation of Benzimidazole Nucleosides with the Aid of Model Analogues

1981 ◽  
Vol 36 (1-2) ◽  
pp. 126-134 ◽  
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.

13C, 29Si, 115Sn, 117Sn and 119Sn NMR spectra of some triphenyl derivatives of elements of IVB group

1981 ◽  
Vol 46 (6) ◽  
pp. 1383-1388 ◽  
Author(s):  
Antonín Lyčka ◽  
Dobroslav Šnobl ◽  
Karel Handlíř ◽  
Jaroslav Holeček ◽  
Milan Nádvorník
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
119Sn Nmr ◽  
Type C ◽  
Derivatives Of

13C, 29Si and Sn NMR spectra of ten compounds type (C6H5)3XY, four compounds type ((C6H5)3XO)2CrO2 and - for comparison - two compounds type (CH3CH2CH2CH2)3SnY and ((CH3CH2CH2CH2)3SnO)2CrO2 (X are elements of IVB group) have been measured in deuteriochloroform. The respective chemical shifts, absolute values of coupling constants nJ(119Sn13C) and 2J(119Sn117Sn) are given.

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