THE PROTON RESONANCE SPECTRA AND STRUCTURES OF SUBSTITUTED AZULENES IN TRIFLUOROACETIC ACID

1962 ◽  
Vol 40 (9) ◽  
pp. 1777-1785 ◽  
Author(s):  
S. S. Danyluk ◽  
W. G. Schneider
Keyword(s):  
Trifluoroacetic Acid ◽  
Membered Ring ◽  
Coupling Constants ◽  
Electron Charge ◽  
Proton Resonance ◽  
Charge Densities ◽  
Electron Deficiency

The proton resonance spectra for a number of substituted azulenes and their conjugate acids are reported at 22 °C. From the spectra for the conjugate acids it is confirmed that monoprotonation occurs in the five-membered ring in each case. The unit electron deficiency is shown to be mainly localized in the seven-membered ring of the ion.Chemical shift changes on protonation are interpreted qualitatively in terms of changes in local π electron charge densities on the carbon atoms.Unusually large values are noted for the coupling constants between protons on the five-membered ring of the cations and are attributed in part to hyperconjugative effects.

Protonenresonanz-spektroskopische Untersuchungen am 1.2-Diphenyl-cyclobutadien-eisentricarbonyl. Ein Beitrag zur Kenntnis der Bindungsverhältnisse im komplex-gebundenen Cyclobutadien / The Proton Resonance Spectrum of 1,2-Diphenyl-cyclobutadiene-irontricarbonyl. An Investigation on Bonding Properties in Complex Stabilized Cyclobutadiene

1971 ◽  
Vol 26 (6) ◽  
pp. 570-576 ◽  
Author(s):  
Hans Albert Brune ◽  
Hans Hüther ◽  
Hans Hanebeck
Keyword(s):  
Resonance Spectrum ◽  
Membered Ring ◽  
Coupling Constants ◽  
Bond Orders ◽  
Proton Resonance ◽  
Carbon Carbon Bonds ◽  
Carbon Bonds ◽  
Bonding Properties ◽  
Single Bonds

The complete proton resonance spectrum of 1.2-diphenyl-cyclobutadiene-irontricarbonyl was measured including all observable 13C-H-coupling constants within the four-membered ring. The couplings were assigned. Their analysis excludes the structure of a rectangular cyclobutadiene with alternating double and single bonds; the carbon-carbon bonds of the four-membered ring have nearly uniform bond orders.

Erratum: Electron charge densities at conduction-band edges of semiconductors

1987 ◽  
Vol 35 (17) ◽  
pp. 9308-9309
Author(s):  
Steven L. Richardson ◽  
Marvin L. Cohen ◽  
Steven G. Louie ◽  
James R. Chelikowsky
Keyword(s):  
Conduction Band ◽  
Electron Charge ◽  
Charge Densities

Strongly hindered rotation in α,α,2,6-terrachlorotoluene. Stereospecific five-bond coupling. Hyperconjugative contributions to long-range sidechain-ring proton coupling constants

1968 ◽  
Vol 46 (12) ◽  
pp. 2187-2188 ◽  
Author(s):  
T. Schaefer ◽  
R. Schwenk ◽  
C. J. Macdonald ◽  
W. F. Reynolds
Keyword(s):  
Free Energy ◽  
Resonance Spectrum ◽  
Coupling Constants ◽  
Proton Resonance ◽  
Kcal Mole ◽  
Hindered Rotation ◽  
Ring Proton ◽  
Meta Position ◽  
Proton Coupling ◽  
Free Energy Of Activation

At −40 °C the C—H bond of the dichloromethyl group of α,α,2,6-tetrachlorotoluene lies in the plane of the ring. The proton resonance spectrum demonstrates a stereospecific five-bond coupling between the C—H proton and the ring proton in the meta position. The coupling to the para proton is essentially zero as expected from a hyperconjugative mechanism. The free energy of activation of rotation of the dichloromethyl group is about 15 kcal/mole at 25 °C.

THE ANALYSIS OF NUCLEAR MAGNETIC RESONANCE SPECTRA: III. PYRIDINE AND DEUTERATED PYRIDINES

1957 ◽  
Vol 35 (12) ◽  
pp. 1487-1495 ◽  
Author(s):  
W. G. Schneider ◽  
H. J. Bernstein ◽  
J. A. Pople
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Resolution ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Calculated Spectrum ◽  
Proton Resonance ◽  
Nuclear Magnetic Resonance Spectra ◽  
Spin Coupling Constants

The proton resonance spectra of pyridine, 2,6-pyridine-d2, 3-pyridine-d1, and 4-pyridine-d1 have been obtained for the pure liquids under conditions of high resolution. The spectra have been analyzed as proton groupings of AB2X2, AB2, perturbed ABX, and B2X2 respectively. The spin-coupling constants obtained from analysis of the simpler spectra of the deuterated molecules were used to suggest trial solutions for the analysis of the complicated AB2X2 spectrum of pyridine. A final set of chemical shifts and spin-coupling constants derived for pyridine give satisfactory agreement between the observed and calculated spectrum.

ChemInform Abstract: DIHEDRAL ANGULAR DEPENDENCE OF H-N-C-H COUPLING CONSTANTS, PROTONATED AMINES IN TRIFLUOROACETIC ACID

1973 ◽  
Vol 4 (44) ◽  
pp. no-no
Author(s):  
ROBERT R. FRASER ◽  
ROGER N. RENAUD ◽  
JOHN K. SAUNDERS ◽  
YUK Y. WIGFIELD
Keyword(s):  
Angular Dependence ◽  
Trifluoroacetic Acid ◽  
Coupling Constants ◽  
Protonated Amines

P.M.R. spectra of heteroaromatic molecules containing bridgehead nitrogen atoms. V. Pyrrolo[a]quinoline

1976 ◽  
Vol 29 (4) ◽  
pp. 847 ◽  
Author(s):  
ML Heffernan ◽  
GM Irvine
Keyword(s):  
Ambient Temperature ◽  
Spin System ◽  
Variable Temperature ◽  
Membered Ring ◽  
Coupling Constants ◽  
Ring Proton ◽  
Temperature Study ◽  
Proton Resonances ◽  
Cdcl3 Solution ◽  
Bridgehead Nitrogen

The p.m.r. spectra of (CD3)2SO and CDCl3 solutions of pyrrolo[a]quinoline, a nine-spin system, have been analysed. In the former case, the various multiplets were sufficiently non-overlapping for detailed double-irradiation experiments to be performed in order to confirm the proton assignments and to determine the magnitudes and relative signs of several inter-ring coupling constants. For the CDCl3 solution, it was found that there was broadening of the five-membered ring proton resonances at ambient temperature. A variable-temperature study showed that the broadening was arising from the exchange of the H1 and H3 protons and that the effects of exchange could be avoided by running the spectra at or below -20�.

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