Conformational dependence of vinyl proton long-range coupling constants in styrenoic system. An application of solvent and temperature dependence of parabenzylic coupling constant for determination of torsional barriers

1988 ◽  
Vol 78 (1) ◽  
pp. 9-22 ◽  
Author(s):  
Reino Laatikainen ◽  
Erkki Kolehmainen ◽  
Tauno Kuokkanen ◽  
Kari Tuppurainen
Keyword(s):  
Temperature Dependence ◽  
Long Range ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Vinyl Proton

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.

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.

Studies on the PMR Spectra of Oxetanes. VI 2-(3-Chlorophenyl)oxetane and 2-(2-Chlorophenyl)oxetane at 60 and 100 MHz

1974 ◽  
Vol 29 (12) ◽  
pp. 1902-1906 ◽  
Author(s):  
Jukka Jokisaari
Keyword(s):  
Long Range ◽  
Chemical Shifts ◽  
Methine Proton ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Proton Proton ◽  
Temperature Range ◽  
Proton Coupling ◽  
Phenyl Proton ◽  
Pmr Spectra

The 100 MHz spectra of the phenyl protons in 2-(3-chlorophenyl) oxetane and 2-(2-chlorophenyl) oxetane have been analysed. The 60 MHz PMR chemical shifts and proton-proton coupling constants have been studied in the temperature range from -20 C to +80 °C. The chemical shifts were sensitive to temperature, while the coupling constants were not, except the long range 5Jm coupling constant between the methine proton and the meta positioned phenyl proton in 2-(2-chlorophenyl) oxetane.

An Investigation of Substituent Effects on Coupling Constants to Vinyl Protons in Styrene Derivatives

1974 ◽  
Vol 52 (19) ◽  
pp. 3415-3423 ◽  
Author(s):  
William F. Reynolds ◽  
Ian R. Peat ◽  
Gordon K. Hamer
Keyword(s):  
Long Range ◽  
Substituent Effects ◽  
Phenyl Group ◽  
Coupling Constants ◽  
Vinyl Proton ◽  
Model Compounds ◽  
Proton Coupling ◽  
Phenyl Proton ◽  
Styrene Derivatives ◽  
Induced Changes

Experimental long-range phenyl proton–vinyl proton coupling constants in 4-substituted styrenes are substituent independent. This is also predicted by INDO–finite perturbation theory calculations of these coupling constants. Comparison with calculated and experimental long-range coupling constants for 4-substituted benzaldehydes suggests that the previously reported substituent dependence for the latter coupling constants arises from substituent-induced changes in molecular geometry.Geminal vinyl coupling constants in 4-substituted styrenes, α-methylstyrenes, and α-t-butylstyrenes are substituent dependent with substituent effects increasing as phenyl and vinyl groups are twisted out of planarity. These trends are reproduced by INDO–FPT calculations. It is concluded that the substituent effects are primarily transmitted through space.Both experimental and calculated vinyl 13C–1H coupling constants show strong stereospecific substituent effects. From the pattern of results (particularly the greater field dependence for JC(β)H(9) than JC β)H(8)) it is concluded that these coupling constants.also reflect through-space substituent effects. This is supported by calculations on model compounds with no intervening phenyl group.

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