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.

NMR Spectroscopic Studies of Thialene (Cyclopenta[b]thiapyran) and Isothialene (Cyclopenta[c]thiapyran)

1993 ◽  
Vol 58 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Robert F. X. Klein ◽  
Václav Horák ◽  
Arthur G. Anderson
Keyword(s):  
Chemical Shift ◽  
Bond Order ◽  
Spectroscopic Studies ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Vicinal Coupling Constant ◽  
Spectral Parameters ◽  
First Order ◽  
Nmr Techniques ◽  
C Nmr

1H and 13C NMR spectral parameters are reported for the S-pseudoazulenes thialene (cyclopenta[b]thiapyran) (I) and isothialene (cyclopenta[c]thiapyran) (II). Both compounds display complex first order spectra, with thialene having 10 and isothialene 14 of 15 possible coupling constants. Complete unambiguous assignments of all protons and non-quaternary carbons were made via 2-dimensional NMR techniques and PPP-SCF π-electron density/chemical shift and π-bond order/vicinal coupling constant correlations.

C13 SPLITTINGS IN SOME SUBSTITUTED BENZENES

1962 ◽  
Vol 40 (9) ◽  
pp. 1758-1762 ◽  
Author(s):  
H. M. Hutton ◽  
W. F. Reynolds ◽  
T. Schaefer
Keyword(s):  
Long Range ◽  
Electron Acceptors ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Substituted Benzenes ◽  
First Order ◽  
Proton Coupling

C13 sidebands in the proton spectra of some symmetrically substituted benzenes have been used to obtain carbon–hydrogen coupling constants as well as proton coupling constants.A long-range carbon–hydrogen coupling constant has also been found. Substituents which act as electron acceptors in an inductive manner are found to increase the C13H coupling constants by as much as 20 c.p.s. The patterns of the sidebands are discussed and possible errors in first-order analyses are indicated.

Effect of solvent and temperature upon the rotationally averaged vicinal coupling constants of some substituted 1,2-dibromoethanes

1969 ◽  
Vol 47 (8) ◽  
pp. 1295-1309 ◽  
Author(s):  
W. F. Reynolds ◽  
D. J. Wood
Keyword(s):  
Coupling Constants ◽  
Dipolar Interactions ◽  
Coupling Constant ◽  
Vicinal Coupling Constant ◽  
Factors Affecting ◽  
Relative Stabilities ◽  
Vicinal Coupling Constants ◽  
Solvent Dependence ◽  
Rotational Equilibrium ◽  
The Difference

The solvent dependence of vicinal coupling constants has been investigated for (1,2-dibromoethyl)-benzene and three of its 4-substituted derivatives and for threo- and erythro(1,2-dibromopropyl)benzene. The temperature dependence of the vicinal coupling constants of three of the compounds has also been investigated. The difference between the two vicinal coupling constants of (1,2-dibromoethyl)benzene is dependent upon solution dielectric constant (in non-aromatic solvents) while the sum of coupling constants remains constant. The relative stabilities of its three rotamers are deduced from this information. A polar substituent in the 4-position does not affect the rotational equilibrium in any predictable manner. The vicinal coupling constant of threo(1,2-dibromopropyl)benzene is strongly solvent dependent. The relative stabilities of its three rotamers are deduced from the observation that the vicinal coupling constant is temperature independent. The most stable rotamer of erythro(1,2-dibromopropyl)-benzene is deduced from the observation that the vicinal coupling constant is large and independent of solvent. Factors affecting conformational preference are deduced. It is concluded that dipolar interactions are as important as steric interactions.

Stereoselective synthesis and stereochemistry of r-2-alkoxycarbonyl-c-3-o-substituted phenyl-1,4-thiazane 1,1-dioxides

2005 ◽  
Vol 83 (3) ◽  
pp. 202-208
Author(s):  
N Bhavani ◽  
S Perumal ◽  
R Banureka
Keyword(s):  
Long Range ◽  
Trans Isomer ◽  
Stereoselective Synthesis ◽  
Nmr Assignments ◽  
Chair Conformation ◽  
Coupling Constant ◽  
Vicinal Coupling Constant ◽  
Relative Configuration ◽  
Cis Isomer ◽  
C Nmr

r-2-Alkoxycarbonyl-c-3-aryl-1,4-thiazane 1,1-dioxides were obtained as the stereoselective product, when the aldehyde used was o-substituted benzaldehyde while the p-substituted benzaldehydes gave a trans product. The relative configuration of the adjacent alkoxycarbonyl and aryl groups was assigned from the vicinal coupling constant, 3J = 10.6 Hz in the trans isomer and 3.2 Hz in the cis isomer, and from the multiplicity pattern, i.e., a doublet for the H-2 proton of the trans isomer and a triplet for the H-2 proton of the cis isomer. The unusual, large long-range coupling (4J = 2.8 Hz) because of the "W" arrangement between H-2e and H-6e across the ring type was very useful for confirming the cis configuration and chair conformation of the isomer. The various 1H and 13C NMR assignments were made with the help of 1H–1H COSY, 1H–13C COSY, HMBC, and NOESY spectral analyses.Key words: 1H and 13C NMR, 1H–1H COSY, 1H–13C COSY, HMBC, NOESY, stereoselectivity, 1,4-thiazane.

Analysis of the NMR Spectrum of Phenylethane-1,2-Dithiol

1965 ◽  
Vol 19 (4) ◽  
pp. 124-129 ◽  
Author(s):  
J. W. Forbes ◽  
J. L. Jungnickel
Keyword(s):  
Computer Program ◽  
Experimental Evidence ◽  
Long Range ◽  
Coupling Constants ◽  
Positive Sign ◽  
Coupling Constant ◽  
Hydrogen Atoms ◽  
Nmr Spectrum ◽  
Geminal Coupling ◽  
Sign Alternation

The NMR spectrum of phenylethane-1,2-dithiol has been analyzed completely (except for the aromatic protons) by Reilly's new computer program MARIPI which is based on the Swalen and Reilly programs NMRIT and NMRENI. The geminal coupling constant, J34, was assumed to be negative in accord with the recent theoretical and experimental evidence on the signs of (H,H) coupling constants. The magnitudes of the two vicinal H-C-C-H coupling constants, J35 and J45, indicate that the molecule exists primarily in the two forms with gauche-trans arrangement of the hydrogen atoms on these carbon atoms The H-C-S-H coupling constants, J13, J14, and J25, can be either positive or negative in sign; however, a positive sign is favored in line with the –, +, – pattern of sign-alternation for (H,H) coupling across 2, 3, and 4 bonds. The long-range coupling constants, J15, J23, and J24, are small and probably negative. The very long-range coupling between the S-H protons, J12, is too small to be determined

Long-range coupling constants for α-13C nuclei in phenyl-X-R (X = O,S,Se,Te) derivatives. Internal rotational information

1988 ◽  
Vol 66 (7) ◽  
pp. 1641-1646 ◽  
Author(s):  
Ted Schaefer ◽  
Glenn H. Penner
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Long Range ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Photoelectron Spectra ◽  
Side Chain ◽  
Coupling Constant ◽  
Stable Conformation ◽  
Nuclear Magnetic

The long-range spin–spin coupling constant over six bonds between the 19F nucleus and the 13C nucleus in the side chain,6J(C,F), is reported for 4—F—C6H4—X—R, where X = O, S and R = CH3, CH2CH3, CH(CH3)2 and C(CH3)3 and 6J(C,F) depends on sin2 θ, where θ is the angle by which the side chain twists out-of-plane about the [Formula: see text] bond. Expectation values of sin2 θ are obtained from 6J(C,F), yielding magnitudes of the apparent twofold barrier to rotation about the [Formula: see text] bond. In these terms, the most stable conformation is that for θ = 0° for all compounds, with the exception of R = C(CH3)3 and of X = S, R = CH(CH3)2; there is effectively free rotation about the [Formula: see text] bond in isopropyl 4-fluorophenyl sulfide in acetone-d6 solution. Good correlations exist between 6J(C,F) and a number of other molecular properties, including certain differences of ionization potentials of the molecular orbitals in the ethers. In particular, the chemical shifts of C-4 are correlated with 6J(C,F). Because 5J(C,C), the coupling constant involving C-4, also depends on sin2 θ, it is measured for the methyl and ethyl selenides and tellurides, as are other 13C,13C couplings involving a 13C nucleus in the side chain. The literature values for the 13C nuclear magnetic resonance chemical shifts in alkyl phenyl selenides and tellurides can be related to θ preferences and also allow estimates of the extrema in 5J(C,C). The resultant values of arcsin [Formula: see text] for R = CH3 are in good agreement with estimates of θ obtained from electron diffraction patterns, photoelectron spectra, and nuclear magnetic resonance in the nematic phase.

Long-range spin–spin coupling constants between ring protons and aldehydic protons in some para-substituted benzaldehydes

1969 ◽  
Vol 47 (21) ◽  
pp. 4005-4010 ◽  
Author(s):  
S. S. Danyluk ◽  
C. L. Bell ◽  
T. Schaefer
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Proton Proton ◽  
Proton Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Coupling Mechanisms ◽  
Benzaldehyde Derivatives

The long-range proton–proton coupling constants between the ring protons and the aldehydic proton are reported for a series of para-substituted benzaldehyde derivatives. It was found that JoH,CHO < 0 and JmH,CHO > 0. Furthermore, JoH,CHO increases in magnitude as the electron donating power of the sub-stituent increases. A similar trend is observed forJmH,CHO but the ratio of the increase to the magnitude of JmH,CHO is much less than for JoH,CHO. A good correlation is obtained between JoH,CHO and the sub-stituent parameters of Swain and Lupton.The coupling constant data are discussed in terms of σ and π coupling mechanisms and it is concluded that σ electron mechanisms are dominant for both JoH,CHO and JmH,CHO.

1H and 19F NMR conformational studies of the monofluorostyrenes in solution. Comparison with theory and vapor phase behavior

1990 ◽  
Vol 68 (8) ◽  
pp. 1383-1392 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Side Chain ◽  
Coupling Constant ◽  
Mo Calculations ◽  
Carbon Carbon Bond ◽  
Electron Contribution ◽  
Internal Barriers ◽  
Cis And Trans ◽  
Coupling Mechanisms

The parameters for the high resolution 1H and 19F NMR spectra of 2-, 3-, and 4-fluorostyrene are reported for solutions in CS2 and acetone-d6 at 300 K. The populations of the planar cis and trans conformers of 2- and 3-fluorostyrene are deduced from the long-range coupling constants involving the meta and α protons. These populations are insensitive to solvent and appear to be in reasonable agreement with previous 6-31G MO computations for the free molecule; they are also compared with populations deduced from recent rotational and vibronic spectra. The long-range coupling constants for the protons of 4-fluorostyrene imply an internal barrier to rotation about the exocyclic carbon–carbon bond very similar to that in styrene, in agreement with the 6-31G results. The signs of the coupling constants involving 19F and the protons in the side chain are reported and discussed in terms of coupling mechanisms for the three molecules. An earlier surmise, of a positive a electron contribution to the coupling constant over six bonds in an all-trans arrangement, is confirmed for the meta and trans-β protons in 3-fluorostyrene. Keywords: monofluorostyrenes, 1H and 19F NMR, conformations, long-range coupling mechanisms, MO calculations of internal barriers.

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