An Investigation of Long-range Proton–Proton Coupling Constants in Phenylacetylene Derivatives

1972 ◽  
Vol 50 (13) ◽  
pp. 2035-2040 ◽  
Author(s):  
C. J. MacDonald ◽  
G. K. Hamer ◽  
I. R. Peat ◽  
W. F. Reynolds
Keyword(s):  
Hyperfine Interaction ◽  
Long Range ◽  
Excellent Agreement ◽  
Quantitative Estimation ◽  
Theoretical Calculations ◽  
Experimental Results ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling

Signs and magnitudes of long-range coupling constants in three phenylacetylene derivatives have been determined. Values of the coupling constants are discussed in terms of the McConnell formulation and compared with results of MO–INDO–FPT calculations. Coupling constants are dominated by π contributions. Estimated values of hyperfine interaction constants for acetylene and methylacetylene groups are respectively QCC≡CH = −12 and QCC≡CCH = +12 G. The theoretical calculations are in excellent agreement with experimental results. Both approaches allow quantitative estimation of nine bond couplings in 4-vinylphenylacetylene.

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.

Long-range Proton–Proton Coupling Constants in the Vinylpyridines. Conformational Preferences of the Vinyl Group and Molecular Orbital Calculations

1974 ◽  
Vol 52 (1) ◽  
pp. 136-142 ◽  
Author(s):  
J. Brian Rowbotham ◽  
Ted Schaefer
Keyword(s):  
Molecular Orbital ◽  
Long Range ◽  
Coupling Constants ◽  
Graphical Form ◽  
Molecular Orbital Calculations ◽  
Proton Proton ◽  
Meta Position ◽  
Proton Coupling ◽  
Conformational Preferences ◽  
Vinyl Group

The p.m.r. spectra of 2-vinylpyridine, 2-methyl-5-vinylpyridine, and 4-vinylpyridine are examined for long-range coupling constants between the vinylic and ring protons. Those over six, seven, and eight bonds from the vinyl group to ring or methyl protons in the para position are dominated by a π electron mechanism. Those over five bonds between the α proton and a ring proton in the meta position indicate that the vinyl group prefers to lie cis to the nitrogen in 2-vinylpyridine but trans in the 5-vinylpyridine. INDO-MO-FPT calculations of coupling constants between vinyl protons and ring protons, carbon-13, and nitrogen-14 nuclei are presented in graphical form.

Long-Range proton-proton coupling constants. I. Propanic coupling involving a methyl group4JMeH

1989 ◽  
Vol 10 (7) ◽  
pp. 887-895 ◽  
Author(s):  
Angel L. Esteban ◽  
Maria P. Galache ◽  
Francisco Mora ◽  
Ernesto Diez ◽  
Jesus San Fabian
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling

The conformational distribution of 2-cyanobenzaldehyde and 3-cyanobenzaldehyde in solution and in the vapor

1991 ◽  
Vol 69 (7) ◽  
pp. 1039-1046 ◽  
Author(s):  
Ted Schaefer ◽  
Kerry J. Cox ◽  
Rudy Sebastian
Keyword(s):  
Long Range ◽  
Dipole Moments ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Orbital Theory ◽  
Spectral Parameters ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
Spin Spin Coupling

The 1H nuclear magnetic resonance spectra of 2-cyanobenzaldehyde (2CNB) and 3-cyanobenzaldehyde (3CNB) in CS2/C6D12 and acetone-d6 solutions at 300 K yield precise stereospecific long-range proton–proton coupling constants. These are used to establish the conformational population of the o-cis and o-trans conformers of these relatively polar molecules. For example, the fractional o-cis population of 2CNB changes from 0.12(4) in CS2/C6D12 to 0.46(6) in acetone-d6, whereas that of 3CNB is 0.48(2) in both solvents. Extrapolation to the vapor phase, using a dielectric model, implies a negligible concentration of the o-cis conformer of 2CNB and a roughly 50% abundance of each conformer of 3CNB. Computations at various levels of molecular orbital theory provide estimates of the rotational barrier of the aldehyde moiety and confirm the planar structure of each conformer. The geometries of three conformers are given as obtained from the 6-31G MO basis and may be useful to molecular spectroscopists. Theoretical and experimental dipole moments are interpolated to yield estimates of their magnitudes for the four planar conformers. Somewhat less precise 1H nmr spectral parameters (than for the above solutions) are also obtained for dilute solutions in benzene-d6 at 300 K. The conformational distributions based on these parameters are compared with their only other measurement, based on dipolar moments in benzene at 298 K. Good agreement between the results of the two methods is found for 3CNB but not for 2CNB. It is suggested that specific interactions occur between benzene solvent and solute molecules, particularly for 3CNB, for which these interactions stabilize the conformer having a low dipole moment. Remarkable changes in the intraring proton–proton coupling constants occur in going from CS2/C6D12 to acetone-d6 solution. Key words: 2- and 3-cyanobenzaldehyde (2CNB and 3CNB): 1H NMR, conformations, long-range spin–spin coupling constants, MO computations.

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.

Studies on Prototropic Tautomerism in Neutral and Monoanionic Forms of Pyrimidines by Nuclear Magnetic Resonance Spectroscopy

1977 ◽  
Vol 32 (11-12) ◽  
pp. 894-900 ◽  
Author(s):  
Ryszard Stolarski ◽  
Mieczyslaw Remin ◽  
David Shugar
Keyword(s):  
Quantitative Estimation ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Optical Methods ◽  
Resonance Spectroscopy ◽  
Prototropic Tautomerism ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
Nmr Methods

Abstract NMR methods have been applied to evaluation of prototropic tautomerism, N(1)H ⇌ N (3) H, in several selected pyrimidines, viz. the neutral forms of Isocytosine and 2-alkylthiopyrimidone-4, and the monoanionic forms of uracil, 5-fluorouracil and 4-thiouracil. The predominant tautomeric species of the neutral forms could be estimated only qualitatively from 1H chemical shifts. For the monoanionic forms this procedure was not applicable, for reasons which are discussed in detail. For the monoanionic form of uracil, 13C chemical shifts of C(5) provided a suitable criterion for quantitative estimation of the populations of the two known tautomeric species. However, the potential scope of this procedure appears somewhat limited. By contrast, the values of the vicinal proton-proton coupling constants, J (5,6), provided both necessary and adequate criteria for quantitative evaluation of the tautomer populations for all the neutral and monoanionic forms. The results were in satisfactory agreement with those obtained by optical spectroscopic methods. In some instances the results obtained in this way may be more reliable than those derived from optical methods. The range of applicability, and utility, of NMR methods to studies on protropic tautomerism in pyrimidines are critically assessed.

Experimental and Theoretical Analysis of Vicinal and Long-Range Proton−Proton Coupling Constants for Anthracene Derivatives

2007 ◽  
Vol 111 (33) ◽  
pp. 8264-8270 ◽  
Author(s):  
Ernesto Sánchez-Mendoza ◽  
Jesús Hernández-Trujillo ◽  
Federico del Río-Portilla
Keyword(s):  
Theoretical Analysis ◽  
Long Range ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Anthracene Derivatives
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