P.M.R. spectra of heteroaromatic molecules containing bridgehead nitrogen atoms. I. Tetrazolo[1,5-a]quinoline and 5-Methyltetrazolo[1,5-a]quinoline

1976 ◽  
Vol 29 (4) ◽  
pp. 799 ◽  
Author(s):  
ML Heffernan ◽  
GM Irvine
Keyword(s):  
Nitrogen Atom ◽  
Long Range ◽  
Coupling Constants ◽  
Triple Resonance ◽  
Relative Sign ◽  
Coupling Constant ◽  
Triple Resonance Experiments ◽  
Aromatic Molecules ◽  
Bridgehead Nitrogen

This paper is the first of a series dealing with the analysis of the 100-MHz p.m.r, spectra of hetero-aromatic molecules containing a bridgehead nitrogen atom as part of the conjugated system, e.g. pyrrolo[l,2-a]quinoline. The spectra of the aza-substituted derivatives tetrazolo[l,5-a]quinoline and 5-methyltetrazolo[l,5-a]quinoline in Me2SO and CDCl3 solutions are analysed in detail. Special attention was directed to the determination of the long-range inter-ring coupling constants and their relative signs by multiple-resonance techniques. The analysis of the spectrum of the 5-methyl compound was considerably simplified by decoupling of the methyl protons from the remainder. Evidence was found for a five-bond long-range coupling constant, J4,6, and a seven-bond coupling constant, J4,8 both having a magnitude around 0.3 Hz. Selective double and triple resonance experiments indicated that the relative sign of both of these long-range coupling constants was positive.

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.

P.M.R. spectra of heteroaromatic molecules containing bridgehead nitrogen atoms. II. 5-Methyl-s-triazolo[4,3-a]quinoline and s-Triazolo[4,3-a]quinoline

1976 ◽  
Vol 29 (4) ◽  
pp. 815 ◽  
Author(s):  
ML Heffernan ◽  
GM Irvine
Keyword(s):  
Chemical Shift ◽  
Detailed Analysis ◽  
Long Range ◽  
Coupling Constants ◽  
Order Effects ◽  
Relative Sign ◽  
First Order ◽  
Multiple Resonance ◽  
Bridgehead Nitrogen ◽  
Small Chemical

A detailed analysis of the spectra of 5-methyl-s-triazolo[4,3-a]quinoline and s-triazolo[4,3-a]quinoline in CDCl3 and (CD3)2SO solution was carried out. Measurements were made over a range of temperatures, and multiple-resonance experiments carried out as aids to the confirmation of assignments. The peaks in the spectrum corresponding to H8 were observed to show non-first-order effects, arising from long-range coupling to H4, which were dependent upon the temperature at which the spectrum was obtained. It was found that these effects arose from the variation in the relatively small chemical shift between H6 and H9 and furthermore that the experimental splitting pattern could be used to determine the relative signs of J4,6 and J4,8. Confirmation was obtained that these two coupling constants have the same relative sign.

Notizen: Determination of Signs of Coupling Constants for (Ethene)bis- (triphenylphosphane)platinum(0)

1997 ◽  
Vol 52 (8) ◽  
pp. 1019-1022 ◽  
Author(s):  
Bernd Wrackmeyer
Keyword(s):  
Coupling Constants ◽  
Triple Resonance ◽  
Two Dimensional ◽  
Triple Resonance Experiments

The signs of coupling constants [ 1J(195Pt,13C) (> 0), 2J(195Pt,1H) (< 0), ∑2J (31P,13C)trans + 2J(31P,13C)cis (> 0) and ∑3J(31P,1H )trans +3J(31P,1H)cis (< 0)] in (ethene)bis(triphenylphosphane) platinum (0) (1) were determined by selective heteronuclear double and triple resonance experiments of the type 1H{31P}, 13C{1H,31P} and two-dimensional heteronuclear shift correlations (HETCOR) of the type 13C/1H, 195Pt/1H, and 31P/1H, either by observing the heteronucleus or 1H in the more sensitive inverse mode.

P.M.R. spectra of heteroaromatic molecules containing bridgehead nitrogen atoms. III. Pyrrolo[2,1-c][1,2,4]benzotriazine

1976 ◽  
Vol 29 (4) ◽  
pp. 827 ◽  
Author(s):  
ML Heffernan ◽  
GM Irvine
Keyword(s):  
Acetic Acid ◽  
Acid Solution ◽  
Long Range ◽  
Acetic Acid Solution ◽  
Dimethyl Sulphoxide ◽  
Coupling Constants ◽  
Relative Sign ◽  
Favourable Case ◽  
Bridgehead Nitrogen

The detailed assignment and analysis of the p.m.r. spectra of solutions of pyrrolo[2,1-c][1,2,4]benzotriazine in dimethyl sulphoxide at 80� and 100�, and in acetic acid at 60�, was carried out. The presence and approximate magnitudes of several inter-ring long-range coupling constants were deduced by comparison of the experimental and theoretically calculated spectra. Spin-tickling experiments were used to determine the relative sign combinations of the intra-ring coupling constants of the protons 1-3 and 6-9 in the particularly favourable case of the acetic acid solution of pyrrolo[2,1-c][1,2,4]benzotriazine. All coupling constants were found to have the same sign, presumably positive.

Long-range coupling and conformation in some thienylmethylene and furfurylidene derivatives

1977 ◽  
Vol 30 (2) ◽  
pp. 357 ◽  
Author(s):  
GC Brophy ◽  
PJ Newcombe ◽  
RK Norris
Keyword(s):  
Aromatic Ring ◽  
Long Range ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Vicinal Coupling Constant

The p.m.r, spectra of 12 2-thienylmethylene and furfurylidene derivatives are reported. The average conformation about the Ar-CHXY bond is deduced from the magnitude of the meta (and ortho) long-range benzylic coupling constants. In thiophens, conformations in which the benzylic hydrogen is in or near the plane of the aromatic ring and anti to the ring sulphur are preferred. In furans the hydrogen-in-plane conformations are again favoured. The signs of the meta and ortho benzylic coupling constants have been determined and are positive and negative respectively with respect to the vicinal coupling constant J3,4.

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