Nuclear magnetic resonance spectra of the epihalohydrins. I. Signs of long-range spin–spin coupling constants in epichlorohydrin

1970 ◽  
Vol 48 (7) ◽  
pp. 1033-1045 ◽  
Author(s):  
C. J. Macdonald. ◽  
T. Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Program Analysis ◽  
Benzene Solution ◽  
Chemical Shifts ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Complete Analysis ◽  
Acetonitrile Solution ◽  
Ambiguous Result

The complete analysis of the proton magnetic resonance spectrum of epichlorohydrin as 10 mole% solutions in benzene and in acetonitrile is reported. Extensive tickling experiments demonstrate that the cisoid coupling constants over four bonds are negative, while the corresponding transoid coupling constants are positive. Detailed results for the benzene solution, in which the non-equivalent protons of the —CH2Cl moiety have almost identical chemical shifts, show that although all the resonances may be unequivocally identified and measured to a high order of precision (± 0.03 Hz), an iterative computer fit (LAOCOON-3) has a larger uncertainty for the derived parameters than indicated by the "probable errors" furnished by the computer program. Analysis of the acetonitrile solution, however, furnishes a less ambiguous result. In addition, it is noted that use of relative apparent intensities of resonance peaks can lead to the wrong sign of those coupling constants whose magnitudes are near zero.

Determination of the molecular conformation of uridine in aqueous solution by proton magnetic resonance spectroscopy. Comparison with β-pseudouridine

1970 ◽  
Vol 48 (18) ◽  
pp. 2866-2870 ◽  
Author(s):  
Barry J. Blackburn ◽  
Arthur A. Grey ◽  
Ian C. P. Smith ◽  
Frank E. Hruska
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Molecular Conformation ◽  
Chemical Shifts ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Resonance Spectroscopy ◽  
Proton Coupling ◽  
Anti Conformation

A complete analysis of the 220 MHz proton magnetic resonance spectrum of aqueous uridine is reported. From the data a model for the molecular conformation is presented and compared with that of β-pseudouridine. It is concluded that in both compounds the ribose rings are in rapid equilibrium between classical puckered structures. The temperature-independence of the ribose proton coupling constants and chemical shifts suggests that all the conformers involved in this equilibrium have very similar energies. Both compounds exhibit a preference for the gauche–gauche rotamer about the exocyclic 4′—5′ bond; this conclusion is shown to be independent of the parameters in the Karplus equation or the energy minima chosen for the rotamers. The anti conformation of the uracil base is shown to exist in both compounds. It is proposed that the special structural significance of β-pseudouridine in transfer RNA must be due to the potential hydrogen bond that may be formed by the nitrogen atom at position one in uracil.

THE ANALYSIS OF NUCLEAR MAGNETIC RESONANCE SPECTRA: III. PYRIDINE AND DEUTERATED PYRIDINES

1957 ◽  
Vol 35 (12) ◽  
pp. 1487-1495 ◽  
Author(s):  
W. G. Schneider ◽  
H. J. Bernstein ◽  
J. A. Pople
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Resolution ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Calculated Spectrum ◽  
Proton Resonance ◽  
Nuclear Magnetic Resonance Spectra ◽  
Spin Coupling Constants

The proton resonance spectra of pyridine, 2,6-pyridine-d2, 3-pyridine-d1, and 4-pyridine-d1 have been obtained for the pure liquids under conditions of high resolution. The spectra have been analyzed as proton groupings of AB2X2, AB2, perturbed ABX, and B2X2 respectively. The spin-coupling constants obtained from analysis of the simpler spectra of the deuterated molecules were used to suggest trial solutions for the analysis of the complicated AB2X2 spectrum of pyridine. A final set of chemical shifts and spin-coupling constants derived for pyridine give satisfactory agreement between the observed and calculated spectrum.

PREFERRED RESIDENCE CONFORMATIONS OF DIASTEREOISOMERIC α–β AMINO ALCOHOLS: AN N.M.R. STUDY OF THE EPHEDRINES

1961 ◽  
Vol 39 (12) ◽  
pp. 2536-2542 ◽  
Author(s):  
J. B. Hyne
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Amino Alcohols ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Nuclear Magnetic

Nuclear magnetic resonance spectral results including chemical shifts, anisotropy effects, spin coupling constants, and hydrogen bonding phenomena are presented for the diastereoisomeric pair of α–β amino alcohols (−)-ephedrine and (+)-Ψ-ephedrine. The results are shown to be in keeping with the existence of a preferred residence conformation for each of the diastereoisomers.

scholarly journals Proton Magnetic Resonance Spectrum of 1-Penten-3-yne. INDO and CNDO/2 Molecular Orbital Calculations on Long-Range Spin–Spin Coupling Constants in Enynes

1972 ◽  
Vol 50 (12) ◽  
pp. 1863-1867 ◽  
Author(s):  
L. Ernst ◽  
H. M. Hutton ◽  
T. Schaefer
Keyword(s):  
Molecular Orbital ◽  
Long Range ◽  
Benzene Solution ◽  
Parent Compound ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The high resolution p.m.r. spectra of 1-penten-3-yne in carbon disulfide and in benzene solution are analyzed. Long-range spin–spin coupling constants are discussed in terms of σ and π electron contributions. Comparisons are made with the isomeric 2-methyl-1-buten-3-yne and the parent compound, vinylacetylene. The results of INDO and CNDO/2 molecular orbital calculations are compared to the experimental coupling constants. It is concluded that the π electron contribution to 5J in enyne systems is +0.6 to 0.7 Hz and that σ electron contributions are rather small, the transoid ("pseudo-zig–zag") being larger than the cisoid one. Observed allylic coupling constants in the propene derivative are compared with the calculated values, including those for propene and 2-cyanopropene, available in the literature.

13C nuclear magnetic resonance spectra of 3,6-disubstituted pyridazines

1991 ◽  
Vol 69 (6) ◽  
pp. 972-977 ◽  
Author(s):  
Gottfried Heinisch ◽  
Wolfgang Holzer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13C nuclear magnetic resonance spectra of 17 3,6-disubstituted pyridazine derivatives have been systematically analyzed. Chemical shifts and various 13C, 1H coupling constants are reported. Attempts were made to correlate these data with results obtained from semiempirical molecular orbital calculations as well as with substituent electronegativities and Taft's substituent constants σI and σR0. Key words: 3,6-disubstituted pyridazines, 13C NMR spectroscopy, 13C, 1H spin coupling constants.

Conformational dependence of long-range spin-spin coupling constants in 2,6-dichlorobenzylfluoride

1969 ◽  
Vol 47 (19) ◽  
pp. 3688-3690 ◽  
Author(s):  
T. Schaefer ◽  
C. M. Wong ◽  
K. C. Tam
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Resonance Spectrum ◽  
Double Resonance ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Double resonance experiments on the proton magnetic resonance spectrum of 2,6-dichlorobenzylfluoride yield the signs of the long-range coupling constants between the ring protons and the fluorine nuclei and protons in the fluoromethyl group. The signs and magnitudes of the long-range couplings are discussed in terms of their dependence on the conformation of the fluoromethyl group.

Long-range 13C, 13C spin–spin coupling constants in anisole and some derivatives

1988 ◽  
Vol 66 (7) ◽  
pp. 1635-1640 ◽  
Author(s):  
Ted Schaefer ◽  
Glenn H. Penner
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Methoxy Group ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Nuclear Magnetic

13C nuclear magnetic resonance chemical shifts and nJ(13C,13C) are reported for anisole and 16 of its derivatives, all enriched with 13C in the methoxyl group. 5J(13C,13C) is directly proportional to sin2θ, where θ is the angle by which the methoxy group twists about the C(1)—O bond. In acetone-d6 solution, 5J(C,C) is not observable for a number of 4-substituted anisoles, except for 1,4-dimethoxybenzene. For the latter, 5J(C,C) is compatible with a twofold barrier of 19.3 ± 1.1 kJ/mol hindering rotation about the C(1)—O bond. However, it is unlikely that the barrier is purely twofold in nature. The observed 5J(C,C) is also compatible with 10.5 and 6.0 kJ/mol for the twofold and fourfold components, respectively, implying a dynamical nuclear magnetic resonance barrier of less than 13 kJ/mol. While phase and solvent effects on the internal barrier in anisole are certainly substantial, it appears that a fourfold component must also be present. The apparent twofold barrier in 2,6-difluoroanisole is 5.4 ± 0.9 kJ/mol, based on 5J(C,C) and 6J(H-4,13C). The latter coupling constant is also reported for 1,2,3-trimethoxybenzene and used to deduce its conformation. The θ dependence of 3J(C,C) and 4J(C,C) is briefly discussed for symmetrical anisole derivatives. Differential 13C, 13C isotope shifts are reported for 1,4-dimethoxybenzene.

THE ANALYSIS OF NUCLEAR MAGNETIC RESONANCE SPECTRA: II. TWO PAIRS OF TWO EQUIVALENT NUCLEI

1957 ◽  
Vol 35 (9) ◽  
pp. 1060-1072 ◽  
Author(s):  
J. A. Pople ◽  
W. G. Schneider ◽  
H. J. Bernstein
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Resonance Spectrum ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Complete Analysis ◽  
System A ◽  
Spin Coupling Constants ◽  
Set Up ◽  
Nuclear Magnetic

This paper deals with the analysis of the nuclear magnetic resonance spectrum of two pairs of two equivalent nuclei (of spin [Formula: see text])whose relative chemical shift is of the same order as the spin-coupling constants of the system (A2B2 in the notation of Part I). The complete matrix is set up and correlated with the results of McConnell, McLean, and Reilly (4) for the corresponding theory with large chemical shiftsThe proton resonance spectrum of naphthalene is reported and is analyzed as an A2B2 system on the hypothesis that spin couplings between protons on different rings are negligible. A complete analysis of the spectrum of o-dichlorobenzene, which represents a further example of an A2B2, system, is also given. The spectrum of 1-chloro-2-bromoethane at room temperature is also analyzed as an A2B2 system.

THE PROTON RESONANCE SPECTRA OF SOME SUBSTITUTED FURANS AND PYRROLES

1961 ◽  
Vol 39 (4) ◽  
pp. 905-914 ◽  
Author(s):  
R. J. Abraham ◽  
H. J. Bernstein
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Proton Resonance ◽  
Spin Coupling Constants ◽  
Substituted Furans ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of some substituted furans and pyrroles have been analyzed for spin coupling constants and chemical shifts.The relative insensitivity of the spin coupling constants to the nature of the substituent makes it possible to estimate their values in the parent molecules furan and pyrrole. The magnitude of the spin coupling constants is correlated with the angles made by the CH bonds with the CC bonds of the ring.The chemical shifts are interpreted in terms of an effect due to the electronegativity of the substituent together with the effect due to conjugation with the ring.

Review lecture: Nuclear magnetic resonance spectroscopy in two frequency dimensions

1980 ◽  
Vol 373 (1753) ◽  
pp. 149-178 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Past History ◽  
Dimensional Space ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Resonance Spectroscopy ◽  
Experimental Conditions ◽  
Nuclear Magnetic

A spectrum is normally thought of in terms of a graph of absorption intensity as a function of frequency, and in this form it has served us well for many years. A recent development extends this idea into a second frequency dimension, the spectrum now being represented by a surface in three-dimensional space. The examples are in the field of high resolution nuclear magnetic resonance (n.m.r.) spectroscopy, although the principle is rather more general, being based on the two-dimensional Fourier transformation of a transient response that is a function of two independent time variables t 1 and t 2 . By arranging for different experimental conditions to prevail during t 1 and t 2 , it is possible to separate different n.m.r. parameters, for example chemical shifts and spin coupling constants, into the two frequency dimensions. There is also an important element of correlation involved, since during t 2 the nuclei ‘remember’ their past history during t 1 ,and this has been used to correlate proton and carbon-13 chemical shifts.

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