The Proton Magnetic Resonance Spectrum of p-Methylbenzylbromide, Conformational Preference of the Bromomethyl Rotor

1974 ◽  
Vol 52 (20) ◽  
pp. 3489-3494 ◽  
Author(s):  
Kalvin Chum ◽  
J. Brian Rowbotham ◽  
Ted Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Alternative Model ◽  
Proton Magnetic Resonance ◽  
Resonance Spectrum ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
The Other ◽  
Complete Analysis ◽  
Conformational Preference

A complete analysis is given of the nine-spinproton magnetic resonance spectrum of p-methylbenzyl bromide as a 20 mol% solution in acetone-d6 The long-range coupling constants between methyl and ring protons are the same as those in toluene. The coupling constants between the methylene protons and the other protons in the molecule are consistent with a two-fold barrier of 500 ± 200 cal/mol for the bromomethyl group, the preferred conformation having the C—Br bond in a plane perpendicular to the aromatic plane. An alternative model, in which a C—H bond of the bromomethyl rotor prefers the aromatic plane to the extent of 3 kcal/mol, is considered unlikely.

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.

scholarly journals Proton Magnetic Resonance Spectrum of 2-Chloroaniline-15N. Long-range Coupling Constants to Amino Protons from all Ring Protons

1971 ◽  
Vol 49 (22) ◽  
pp. 3627-3635 ◽  
Author(s):  
R. Wasylishen ◽  
T. Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Resonance Spectrum ◽  
Proton Magnetic Resonance Spectrum ◽  
Proton Exchange ◽  
Coupling Constants ◽  
Amino Group ◽  
Fast Rotation ◽  
The One

The p.m.r. spectra of 2-chloroaniline and 2-chloroaniline-15N in benzene and toluene solutions are analyzed at 60 and 100 MHz under conditions where the amino protons are exchanging intermolecularly and also where they are not exchanging. The spectrum of 2-chloroaniline-H15ND in the absence of amino proton exchange is observed between −48 and 80 °C. In all situations fast rotation about the C—N bond evidently occurs. Long-range couplings of the amino protons to all ring protons are observed and their signs are determined. The nonplanarity of the amino group is discussed in terms of the long-range couplings, of the one-bond 15N–H couplings, and of the two-bond H–H couplings in the amino group. The signs and magnitudes of the coupling constants between the ring protons and 15N are also determined.

Das Protonenresonanzspektrum von orientiertem Benzol in nematisch-kristallinflüssiger Lösung

1965 ◽  
Vol 20 (4) ◽  
pp. 572-580 ◽  
Author(s):  
Alfred Saupe
Keyword(s):  
Magnetic Resonance ◽  
Chemical Shift ◽  
Proton Magnetic Resonance ◽  
Resonance Spectrum ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Scalar Coupling ◽  
Small Temperature ◽  
Theoretical Methods ◽  
Experimental Errors

The proton magnetic resonance spectrum of benzene oriented in a nematic solution is calculated using group theoretical methods. The calculations agree within experimental errors with the spectrum of benzene observed in a nematic solution of 4.4′-di-n-hexyloxy-azoxy-benzene. By an improvement of the temperature homogenity in the sample it was possible to obtain linewidths of only about 5 cps for all lines independent of the splitting. It is confirmed that the signs of the scalar coupling constants between ortho and meta protonpairs are positive. A small temperature dependence of the chemical shift of the benzene protons was found in the nematic solution. It is due to the dependence of the average orientation on the temperature.

Proton magnetic resonance spectrum of 2,6-dichlorobenzaldoxime. Signs and magnitudes of long-range spin–spin couplings. Degree of nonplanarity

1969 ◽  
Vol 47 (19) ◽  
pp. 3707-3709
Author(s):  
T. Schaefer ◽  
R. Wasylishen
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Resonance Spectrum ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constant ◽  
Hydroxyl Proton ◽  
Ring Proton ◽  
Proton Shift

From the sign and magnitude of the coupling constant between the C—H proton in the sidechain and the para ring proton in 2,6-dichlorobenzaldoxime it is estimated that the deviation from coplanarity of the sidechain is at least 40°. The hydroxyl proton shift in dimethylsulfoxide solution of −11.7 p.p.m., relative to internal tetramethylsilane, indicates a cis arrangement of the hydroxyl and aromatic groups.

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.

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