13C nuclear magnetic resonance studies. 61. The effect of solute–solvent association on internal rotation in substituted benzaldehydes

1976 ◽  
Vol 54 (20) ◽  
pp. 3267-3271 ◽  
Author(s):  
R. E. Klinck ◽  
J. B. Stothers
Keyword(s):  
Steric Effect ◽  
Methylene Chloride ◽  
Activation Parameters ◽  
Formyl Group ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
Group Rotation ◽  
Substituted Benzaldehydes ◽  
Nmr Signals ◽  
C Nmr

Complete lineshape analyses of the 13C nmr signals of the ortho and meta carbons have been carried out for two p-substituted benzaldehydes in methylene chloride-d2 and toluene-d8 solutions over a wide temperature range. The activation parameters have been determined for the formyl group rotation and large negative values are found for ΔS≠ when the latter solvent is used. These results suggest that solute–solvent association has a steric effect on the transition state.

13C nuclear magnetic resonance studies. 58. 13C spectra of a variety of bicyclo[2.2.2]octane derivatives. Further definition of the deshielding δ effect

1976 ◽  
Vol 54 (6) ◽  
pp. 917-925 ◽  
Author(s):  
J. B. Stothers ◽  
C. T. Tan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
Definition Of ◽  
C Nmr ◽  
Nuclear Magnetic

The 13C nmr spectra of 35 bicyclo[2.2.2]octane and -octene derivatives have been determined to extend our examinations of the effects of stereochemistry on the shieldings of closely neighboring carbons. This series includes a variety of methyl substituted bicyclooctanols and -octenols as well as the corresponding hydrocarbons and some bicyclooctanones. With the bicyclo[2.2.2]octane skeleton it is possible to examine an array of systems having substituents separated by three and four bonds in a variety of orientations. The interactions, termed γ and δ effects, respectively, produce distinctive shielding variations which are useful for stereochemical elucidations. Particularly interesting are the pronounced shifts observed for the carbons bearing closely neighboring substituents. Characteristically, for vicinal substituents, these carbons are shielded while for syn-axial δ interactions, these carbons are deshielded by as much as 8.6 ppm. The results are compared with the trends found in other sterically crowded Systems.

scholarly journals Complete Assignment of the 1H and 13C NMR Spectra of Carthamin Potassium Salt Isolated from Carthamus Tinctorius L.

2021 ◽  
Author(s):  
Maiko Sasaki ◽  
Keiko Takahashi
Keyword(s):  
Potassium Salt ◽  
Nmr Spectra ◽  
Carthamus Tinctorius ◽  
Ionization Mass ◽  
13C Nuclear Magnetic Resonance ◽  
Complete Assignment ◽  
Pure Product ◽  
Atomic Adsorption Spectroscopy ◽  
Nmr Signals ◽  
C Nmr

Carthamin potassium salt isolated from Carthamus tinctorius L. was purified by an improved traditional Japanese method, without using column chromatography. The 1H and 13C nuclear magnetic resonance (NMR) signals of the pure product were fully assigned using one- and two-dimensional NMR spectroscopy, while the high purity of the potassium salt and deprotonation at the 3’ position of carthamin were confirmed by atomic adsorption spectroscopy and nano-electrospray ionization mass spectrometry.

Proton Magnetic Resonance Studies of Rotational Isomerism in Halotoluene Derivatives. IX. Rotational Barriers and Conformational Energy Differences in α,α,α′,α′,α″,α″, 2,4,6-Nonachloromesitylene

1973 ◽  
Vol 51 (13) ◽  
pp. 2110-2117 ◽  
Author(s):  
J. Peeling ◽  
B. W. Goodwin ◽  
T. Schaefer ◽  
J. B. Rowbotham
Keyword(s):  
Magnetic Resonance ◽  
Carbon Disulfide ◽  
Proton Magnetic Resonance ◽  
Methylene Chloride ◽  
Activation Parameters ◽  
Rotational Isomerism ◽  
Conformational Energy ◽  
The Other ◽  
Free Energies ◽  
Magnetic Resonance Studies

The activation parameters for the rotation of the dichloromethyl groups in the two conformations of α,α,α′,α′,α″,α″,2,4,6-nonachloromesitylene are reported for solutions in toluene-d8 and in methylene chloride. In addition, free energies of activation are given for solutions in bromochloromethane, tri-chloroethylene, and in carbon disulfide. The free energies of activation are lower in the toluene solution than in the other solutions. The entropies of activation are near zero, perhaps slightly negative. The symmetrical conformation is more stable than the unsymmetrical one in all the solvents.

13C nuclear magnetic resonance studies. 55. A comparison of the stereochemical dependence of γ- and δ-substituent effects on 13C shieldings in several norbornanols and norbornenols

1976 ◽  
Vol 54 (8) ◽  
pp. 1211-1221 ◽  
Author(s):  
J. B. Stothers ◽  
C. T. Tan ◽  
K. C. Teo
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Substituent Effects ◽  
Magnetic Resonance Studies ◽  
Considerable Potential ◽  
13C Nuclear Magnetic Resonance ◽  
Insight Into ◽  
C Nmr ◽  
Nuclear Magnetic

The 13C nmr spectra of a series of 50 methyl substituted norbornanols have been determined to gain further insight into the nature of stereochemical effects on the shieldings of carbons having closely neighboring substituents. The relatively rigid norbornyl skeleton permits examination of a variety of orientations of substituents separated by three and four bonds, the γ and δ interactions, respectively. While methyl carbons close to γ substituents exhibit upfield shifts, as is well established, methyl carbons close to δ substituents are significantly deshielded. Even more striking shifts are found for the carbons bearing these closely lying groups. The penultimate carbons in a fragment having a δ interaction between terminal groups show deviations of up to +11 ppm from the shieldings predicted by simple additivity. For fragments having a corresponding γ interaction, the penultimate carbons absorb as much as −10 ppm from the values expected by additivity. These deviations have considerable potential for stereochemical assignments and offer a challenge for theoretical interpretation.Some norbornenols and the acetates of several of the norbornanols were also included in this series and the latter shieldings are compared briefly with those observed for the parent alcohols.

scholarly journals 13C nuclear magnetic resonance studies. 64. The 13C spectra of a variety of bicyclo[3.2.1]octanols

1977 ◽  
Vol 55 (5) ◽  
pp. 841-848 ◽  
Author(s):  
J. B. Stothers ◽  
C. T. Tan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Substituent Effects ◽  
Ring System ◽  
Hydroxyl Group ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Shielding Effects

The 13C nmr spectra of a series of 20 bicyclo[3.2.1]octanols and -octenols have been determined to examine the shielding effects of the hydroxyl group on the skeletal carbons in this ring system. For comparison, the previously unreported data for a few closely related alcohols in the [2.1.1], [2.2.1], and [3.2.2] systems were also collected. The utility of these substituent effects for configuraional and conformational assignments is discussed.

Qinghaosu: 1H and 13C nuclear magnetic resonance spectral assignments and luminescence

1985 ◽  
Vol 63 (11) ◽  
pp. 3070-3074 ◽  
Author(s):  
Wang Zhongshan ◽  
Thomas T. Nakashima ◽  
Karl R. Kopecky ◽  
José Molina
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
13C Nuclear Magnetic Resonance ◽  
Complete Assignment ◽  
Methoxide Ion ◽  
Nmr Signals ◽  
Bright Luminescence ◽  
C Nmr ◽  
Nuclear Magnetic

The complete assignment of the 1H and 13C nmr signals for Qinghaosu 1 has been made. Treatment of 1 with methoxide ion at 80 °C results in bright luminescence when carried out in the presence of fluorescers. Several products are formed when methanol is present, but in toluene only one product is formed when methanol-free methoxide is used. Its structure is tentatively assigned as 1-(1-methoxycarbonylethyl)-2,6-dimethyl-2-hydroxybicyclo[3.3.1]nonan-9-one.

Carbon-13 and nitrogen-14 NMR spectra of 1-(substituted phenyl)pyridinium salts

1980 ◽  
Vol 45 (10) ◽  
pp. 2766-2771 ◽  
Author(s):  
Antonín Lyčka
Keyword(s):  
Heavy Water ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Pyridinium Salts ◽  
Nmr Signals ◽  
C Nmr

The 13C and 14N NMR spectra of 1M solutions of 1-(substituted phenyl)pyridinium salts (4-CH3, 4-OCH3, H, 4-Cl, 4-Br, 4-I, 3-NO2, 4-NO2, 2,4-(NO2)2 (the 13C NMR only)) have been measured in heavy water at 30 °C. The 13C and 14N chemical shifts, the 1J(CH) coupling constants, some 3J(CH) coupling constants, and values of half-widths Δ 1/2 of the 14N NMR signals are given. The 13C chemical shifts of C(4) correlate with the σ0 constants (δC(4) = (1.79 ± 0.097) σ0 + (147.67 ± 0.041)), whereas no correlation of the nitrogen chemical shifts with the σ constants has been found. The half-widths Δ 1/2 correlate with the σ0 constants (Δ 1/2 = (76.2 ± 4.9) σ0 + (106.4 ± 2.2)) except for 1-phenylpyridinium chloride.

X-Ray crystallographic and 13C nuclear magnetic resonance studies of 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-ones derived from ephedrine and pseudoephedrine

Tetrahedron ◽  
2001 ◽  
Vol 57 (49) ◽  
pp. 9789-9798 ◽  
Author(s):  
Shawn R Hitchcock ◽  
George P Nora ◽  
David M Casper ◽  
Michael D Squire ◽  
Christopher D Maroules ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Studies ◽  
X Ray ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

scholarly journals Propionate stimulates pyruvate oxidation in the presence of acetate

2014 ◽  
Vol 307 (8) ◽  
pp. H1134-H1141 ◽  
Author(s):  
Colin Purmal ◽  
Blanka Kucejova ◽  
A. Dean Sherry ◽  
Shawn C. Burgess ◽  
Craig. R. Malloy ◽  
...  
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Energy Production ◽  
Nmr Spectra ◽  
Heart Tissue ◽  
Viable Myocardium ◽  
Normal Heart ◽  
Alternative Substrate ◽  
Isotopomer Analysis ◽  
Nmr Signals ◽  
C Nmr

Flux through pyruvate dehydrogenase (PDH) in the heart may be reduced by various forms of injury to the myocardium, or by oxidation of alternative substrates in normal heart tissue. It is important to distinguish these two mechanisms because imaging of flux through PDH based on the appearance of hyperpolarized (HP) [13C]bicarbonate derived from HP [1-13C]pyruvate has been proposed as a method for identifying viable myocardium. The efficacy of propionate for increasing PDH flux in the setting of PDH inhibition by an alternative substrate was studied using isotopomer analysis paired with exams using HP [1-13C]pyruvate. Hearts from C57/bl6 mice were supplied with acetate (2 mM) and glucose (8.25 mM). 13C NMR spectra were acquired in a cryogenically cooled probe at 14.1 Tesla. After addition of hyperpolarized [1-13C]pyruvate, 13C NMR signals from lactate, alanine, malate, and aspartate were easily detected, in addition to small signals from bicarbonate and CO2. The addition of propionate (2 mM) increased appearance of HP [13C]bicarbonate >30-fold without change in O2 consumption. Isotopomer analysis of extracts from the freeze-clamped hearts indicated that acetate was the preferred substrate for energy production, glucose contribution to energy production was minimal, and anaplerosis was stimulated in the presence of propionate. Under conditions where production of acetyl-CoA is dominated by the availability of an alternative substrate, acetate, propionate markedly stimulated PDH flux as detected by the appearance of hyperpolarized [13C]bicarbonate from metabolism of hyperpolarized [1-13C]pyruvate.

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