Long-range coupling in strained derivatives of the 2,3-diazabicyclo[2.2.1]hept-2-ene radical anion: An EPR, ENDOR and TRIPLE-resonance study

1997 ◽  
pp. 1127-1132 ◽  
Author(s):  
Fabian Gerson ◽  
Coskun Sahin
Keyword(s):  
Long Range ◽  
Radical Anion ◽  
Triple Resonance ◽  
Derivatives Of

scholarly journals Signs of proton–proton and proton–fluorine spin–spin coupling constants in 2-fluoro-3-methylpyridine. Sigma and pi contributions to coupling in a nitrogen heterocycle

1969 ◽  
Vol 47 (9) ◽  
pp. 1507-1514 ◽  
Author(s):  
T. Schaefer ◽  
S. S. Danyluk ◽  
C. L. Bell
Keyword(s):  
Nitrogen Atom ◽  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Nitrogen Heterocycle ◽  
Triple Resonance ◽  
Triple Resonance Experiments ◽  
Proton Proton ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The signs of all proton–proton and proton–fluorine spin–spin coupling constants in 2-fluoro-3-methylpyridine have been determined by double and triple resonance experiments. The signs of the longrange coupling constants, JH,CH3 and JF,CH3 are the same as in fluorotoluene derivatives. Their magnitudes are consistent with the assumption that the nitrogen atom primarily polarizes the σ bonds in the molecule, leaving the π contribution to the long-range coupling relatively unaffected.

scholarly journals The cyclopropylcarbinyl route to γ-silyl carbocations

2019 ◽  
Vol 15 ◽  
pp. 1769-1780 ◽  
Author(s):  
Xavier Creary
Keyword(s):  
Long Range ◽  
Trimethylsilyl Group ◽  
Derivatives Of

The mesylate derivative of cis-1-hydroxymethyl-2-trimethylsilylcyclopropane has been prepared, along with a number of related mesylates and triflates with substituents on the 1-position. These substrates all solvolyze in CD3CO2D to give products derived from cyclopropylcarbinyl cations that undergo further rearrangement to give 3-trimethylsilylcyclobutyl cations. These 3-trimethylsilylcyclobutyl cations are stabilized by a long-range rear lobe interaction with the γ-trimethylsilyl group. When the substituent is electron-withdrawing (CF3, CN, or CO2CH3), significant amounts of bicyclobutane products are formed. The bicyclobutanes are a result of γ-trimethylsilyl elimination from the cationic intermediate that has an unusually long calculated Si–C bond. The solvolysis chemistry of mesylate and triflate derivatives of trans-1-hydroxymethyl-2-trimethylsilylcyclopropane and 1-substituted analogs can be quite different since these substrates do not generally lead to 3-trimethylsilylcyclobutyl cations.

THE STRUCTURE AND STEREOCHEMISTRY OF ATISINE

1964 ◽  
Vol 42 (1) ◽  
pp. 137-149 ◽  
Author(s):  
D. Dvornik ◽  
O. E. Edwards
Keyword(s):  
Long Range ◽  
Rigorous Proof ◽  
Polar Groups ◽  
Detailed Explanation ◽  
Exocyclic Methylene ◽  
Derivatives Of ◽  
Methylene Group ◽  
Absolute Stereochemistry ◽  
Basic Strength

A stereospecific hydration of the exocyclic methylene group of a derivative of the alkaloid atisine has been observed. The product was used to degrade the alkaloid to a tetracyclic phenol. This enabled rigorous proof of the structure and relative and absolute stereochemistry of atisine and related alkaloids. A detailed explanation of the abnormal basic strength and the isomerization of atisine is given. Long-range influence of polar groups on the basic strength of derivatives of the alkaloid is reported.

The proton magnetic resonance spectra of N-nitroso derivatives of sarcosine, proline and iminodiacetic acid

1971 ◽  
Vol 24 (9) ◽  
pp. 1949 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Iminodiacetic Acid ◽  
Conformational Isomerism ◽  
Nitroso Group ◽  
Restricted Rotation ◽  
Derivatives Of ◽  
Shielding Effects ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of various N-nitroso derivatives of sarcosine, L-proline, and iminodiacetic acid, including some protected dipeptides, have been obtained. Magnetic non-equivalence and conformational isomerism arising from restricted rotation of the nitroso group are discussed in relation to the reported behaviour of other nitrosamines. Long-range shielding effects on protons at a considerable distance from the anisotropic nitrosamino centre were readily detected with these compounds.

Chemical Shift. VI. The Long-range Shielding Effects of Ethylene–Ketal and −Thioketal Groups

1971 ◽  
Vol 49 (9) ◽  
pp. 1335-1338 ◽  
Author(s):  
J. W. ApSimon ◽  
H. Beierbeck ◽  
D. K. Todd ◽  
P. V. Demarco ◽  
W. G. Craig
Keyword(s):  
Chemical Shift ◽  
Electric Field ◽  
Long Range ◽  
Field Effect ◽  
Chemical Shifts ◽  
Electric Field Effect ◽  
Electric Dipoles ◽  
Derivatives Of ◽  
Shielding Effects

The calculation of chemical shift values by the method used in parts I–V (1–5) has been extended to a derivation of the shielding effects of the ethylene–ketal and −thioketal groups. For these studies ketal and thioketal derivatives of monoketoandrostanes were prepared. The chemical shifts of the C-18 and -19 methyl protons in these compounds are reported for the solvents CDCl3, CCl4 and benzene.Representing both groups by point dipoles, values for the anisotropies and for K, a parameter descriptive of the electric field effect, were derived for various, coincidental, locations of the magnetic and electric dipoles along the symmetry axes of the two groups.

ChemInform Abstract: The Radical Anion of 1,2:9,10-Dibenzo(2.2)paracyclophane. An ESR, ENDOR, and TRIPLE Resonance Study

ChemInform ◽  
1987 ◽  
Vol 18 (20) ◽  
Author(s):  
F. GERSON ◽  
W. B. JUN. MARTIN ◽  
H. N. C. WONG ◽  
C. W. CHAN
Keyword(s):  
Radical Anion ◽  
Triple Resonance
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