Long-range Spin–Spin Coupling in Pyrimidine Nucleosides

1971 ◽  
Vol 49 (12) ◽  
pp. 2111-2118 ◽  
Author(s):  
Frank E. Hruska
Keyword(s):  
Aqueous Solution ◽  
Long Range ◽  
Spin Coupling ◽  
Bond Orders ◽  
Pyrimidine Nucleosides ◽  
Anti Conformation ◽  
Spin Spin Coupling ◽  
Uracil Base

A study has been made of the 100 MHz p.m.r. spectra of a number of pyrimidine nucleosides in aqueous solution. Long-range five-bond spin–spin coupling interactions between the H-5 and H-1′ hydrogens were noted in uridine, 2′-deoxyuridine, 6-azauridine, and 6-azacytidine and rationalized by a predominantly anti conformation for each nucleoside. The absence of a detectable five-bond coupling in orotidine suggested that the syn conformation is preferred in this instance. The relative magnitudes of the four-bond and five-bond interactions in uridine and pseudouridine were shown to be consistent with the calculated mobile π-bond orders of the C6—N1 and C6—C5 bonds of the uracil base.

Molecular Conformation of 4-Thiouridine in Aqueous Solution

1971 ◽  
Vol 49 (14) ◽  
pp. 2449-2452 ◽  
Author(s):  
F. E. Hruska ◽  
K. K. Ogilvie ◽  
A. A. Smith ◽  
H. Wayborn
Keyword(s):  
Aqueous Solution ◽  
Long Range ◽  
Crystalline State ◽  
Molecular Conformation ◽  
Spin Coupling ◽  
Pyrimidine Nucleoside ◽  
Coupling Interaction ◽  
X Ray ◽  
Anti Conformation ◽  
Spin Spin Coupling

β-4-Thiouridine is a component of several tRNA molecules. A recent X-ray study has shown that this pyrimidine nucleoside favors the syn conformation in the crystalline state. The 100 and 220 MHz p.m.r. data and a comparison with those of uridine are presented here. A long-range five-bond spin–spin coupling interaction between the H-5 and -1′ hydrogens is noted. The results are consistent with an anti conformation for 4-thiouridine in an aqueous solution.

scholarly journals Signs of proton–proton and proton–fluorine spin–spin coupling constants in 2-fluoro-3-methylpyridine. Sigma and pi contributions to coupling in a nitrogen heterocycle

1969 ◽  
Vol 47 (9) ◽  
pp. 1507-1514 ◽  
Author(s):  
T. Schaefer ◽  
S. S. Danyluk ◽  
C. L. Bell
Keyword(s):  
Nitrogen Atom ◽  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Nitrogen Heterocycle ◽  
Triple Resonance ◽  
Triple Resonance Experiments ◽  
Proton Proton ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The signs of all proton–proton and proton–fluorine spin–spin coupling constants in 2-fluoro-3-methylpyridine have been determined by double and triple resonance experiments. The signs of the longrange coupling constants, JH,CH3 and JF,CH3 are the same as in fluorotoluene derivatives. Their magnitudes are consistent with the assumption that the nitrogen atom primarily polarizes the σ bonds in the molecule, leaving the π contribution to the long-range coupling relatively unaffected.

Unresolvable long range spin-spin coupling as a source of systematic error in proton NMR total bandshape analysis

1975 ◽  
Vol 7 (7) ◽  
pp. 307-308 ◽  
Author(s):  
Torbjörn Drakenberg ◽  
Robert E. Carter
Keyword(s):  
Systematic Error ◽  
Long Range ◽  
Proton Nmr ◽  
Spin Coupling ◽  
Spin Spin Coupling

Use of Eu(DPM)3 to study the long-range spin-spin coupling of1H-1H and1H-14N via the PMR spectra

1977 ◽  
Vol 26 (1) ◽  
pp. 176-177
Author(s):  
V. K. Voronov ◽  
V. I. Glukhikh ◽  
E. S. Domnina ◽  
G. G. Skvortsova
Keyword(s):  
Long Range ◽  
Spin Coupling ◽  
Pmr Spectra ◽  
Spin Spin Coupling

Molecular orbital and 1H nuclear magnetic resonance studies of the inversion potentials of thianthrene and thioxanthene

1991 ◽  
Vol 69 (6) ◽  
pp. 927-933 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Christian Beaulieu
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Basis Set ◽  
Basis Sets ◽  
Inversion Barrier ◽  
H Nmr ◽  
Methylene Groups ◽  
Spin Spin Coupling ◽  
Split Valence

The inversion potentials, obtained from STO-3G, STO-3G(*), 3-21G, 3-21G(*), and 4-31G basis sets, are reported for thianthrene and thioxanthene, molecules in which both or only one of the methylene groups have been replaced by sulfur in 9,10-dihydroanthracene. Comparison with the available experimental data suggests that the split-valence bases lead to an overestimate, possibly by about 10 kJ/mol, of the inversion barrier in the crystal, whereas the STO-3G and STO-3G* basis sets underestimate this barrier. It appears that the inversion barrier for thianthrene is much lower in solution than in the crystal. The long-range coupling constants between the methylene and ring protons for thioxanthene in solution are consistent with an inversion barrier somewhat smaller than those obtained with the split-valence bases but rather larger than those predicted with the STO-3G basis set. The bond lengths and angles in the equilibrium structures of the two molecules, as computed with the 3-21G(*) basis, agree reasonably well with those in their crystals, except that the theoretical folding angles are smaller than measured. These discrepancies become less marked when expectation values are calculated from the theoretical inversion potentials at finite temperatures. Key words: MO calculations, inversion potentials of thianthrene and thioxanthene; 1H NMR, thioxanthene; spin–spin coupling constants, long range, in thioxanthene.

Long-range proton spin-spin coupling in rigid cyclic structures by 2D NMR/‘through-space coupling’

1994 ◽  
Vol 32 (1) ◽  
pp. 12-15 ◽  
Author(s):  
Harald Schröder ◽  
Ernst Haslinger
Keyword(s):  
Long Range ◽  
2D Nmr ◽  
Proton Spin ◽  
Spin Coupling ◽  
Spin Spin Coupling

A proton magnetie resonance and molecular orbital study of the conformational preferences of the vinylic fragment in some 2-vinylfurans and in 2-vinylthiophene

1976 ◽  
Vol 54 (20) ◽  
pp. 3216-3223 ◽  
Author(s):  
William J. E. Parr ◽  
Roderick E. Wasylishen ◽  
Ted Schaefer
Keyword(s):  
Molecular Orbital ◽  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Side Chain ◽  
Orbital Theory ◽  
Molecular Orbital Study ◽  
Conformational Preferences ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The stereospecific spin–spin coupling constants over five bonds between the α-proton in the side chain and the protons in the heterocycle in 2-vinylfuran, in its β-nitro and β-aldehydic derivatives, and in 2-vinylthiophene are used to demonstrate the preponderance of the s-trans conformers in polar and nonpolar solutions. These conclusions are compared with predictions made by molecular orbital theory at the STO-3G, INDO, CNDO/2, and MINDO/3 levels. Long-range coupling constants between the protons in the side chain and protons in the heterocycle are calculated by CNDO/2 and INDO–MO–FPT and are compared with experiment. It is concluded that the five-bond couplings involving the α-proton are most sensitive to conformation and that they are transmitted mainly via a σ electron mechanism. The other long-range coupling constants are discussed in terms of σ and π electron mechanisms. The STO-3G calculations yield barriers to internal rotation of greater than 4.8 kcal/mol.

The effects of substituents on the5J long-range spin-spin coupling constants in substituted benzaldehydes

1979 ◽  
Vol 12 (9) ◽  
pp. 542-543 ◽  
Author(s):  
R. H. Contreras ◽  
D. G. de Kowalewski ◽  
A. Osella
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Substituted Benzaldehydes ◽  
Spin Spin Coupling
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