Transmission of a long-range spin-spin interaction between protons by means of the lone pair of electrons of a nitrogen atom in N-vinyl derivatives of heterocycles

1989 ◽  
Vol 38 (11) ◽  
pp. 2317-2320
Author(s):  
A. V. Afonin ◽  
A. V. Vashchenko ◽  
L. A. Es'kova ◽  
B. V. Trzhtsinskaya ◽  
Z. V. Stepanova ◽  
...  
Keyword(s):  
Nitrogen Atom ◽  
Long Range ◽  
Lone Pair ◽  
Spin Interaction ◽  
Vinyl Derivatives ◽  
Derivatives Of

Sigma and Pi Electron Contributions to Long-range Spin–Spin Coupling Constants in the Methyl Derivatives of the Fluoropyridines

1972 ◽  
Vol 50 (14) ◽  
pp. 2344-2350 ◽  
Author(s):  
J. B. Rowbotham ◽  
T. Schaefer
Keyword(s):  
Nitrogen Atom ◽  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
Methyl Group ◽  
Spin Coupling Constants ◽  
Methyl Derivatives ◽  
Spin Spin Coupling ◽  
Derivatives Of

Seven methyl derivatives of the 3- and 4-fluoropyridines are synthesized and their p.m.r. spectra are analyzed. The nuclear spin–spin coupling constants are compared with previous results for the four methyl derivatives of 2-fluoropyridine. A model in which the nitrogen atom polarizes primarily the σ electron system of the ring, leaving the π electron contribution to the coupling mechanism relatively unaffected, qualitatively accounts for the large majority of the coupling constants. For example, the coupling over six bonds between methyl protons and a fluorine nucleus, [Formula: see text] is the same whether the fluorine atom or the methyl group is placed ortho to the nitrogen atom and is little different from its value in p-fluorotoluene. The model is consistent with significant σ electron contributions to long-range couplings over four and five bonds from methyl protons to fluorine nuclei or ring protons. Evidence is adduced for resonance structures in which fluorine conjugates with nitrogen or with ring carbon atoms. An earlier suggestion, that hyperconjugation of the methyl group with nitrogen is necessary to the interpretation of the observed couplings, is dropped. Instead, a substantial polarization of the σ electron core near C-2 and -6 is invoked but apparently does not extend appreciably beyond these atoms in the ring.

ChemInform Abstract: VINYL DERIVATIVES OF 1,2-ISOPROPYLIDENE-D-GLUCOSE 3,5-MONOBORATE

1978 ◽  
Vol 9 (47) ◽  
Author(s):  
V. L. LAPENKO ◽  
B. I. MIKHANT'EV ◽  
V. N. PROKINA
Keyword(s):  
Vinyl Derivatives ◽  
Derivatives Of

Structure and bonding in cyclic phosphoramidates as determined by carbon-13 magnetic resonance

1979 ◽  
Vol 57 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Frederick G. Morin
Keyword(s):  
Magnetic Resonance ◽  
Nitrogen Atom ◽  
Electron Pair ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Ring Conformation ◽  
Delocalized Electron ◽  
Nitrogen Lone Pair ◽  
Structure And Bonding

13C chemical shifts and 13C–31P couplings are reported for 11 cyclic phosphoramidates of ring sizes from four to nine. Vicinal couplings are compared with those of carbocyclic analogs and provide insight regarding the degree of nitrogen lone pair derealization into the N—P bond. For six-membered and larger rings, there appears to be nearly complete lone pair delocalization, i.e., a trigonal planar nitrogen atom. In azetidine derivatives the nitrogen lone pair remains localized, giving rise to a highly puckered ring conformation. Pyrrolidine derivatives are viewed as having a nitrogen with a partially delocalized electron pair.

The Through-Bond Interaction of a Sulfur Lone Pair with Oxygenated Substituents in the Thiacyclohexane Framework

2005 ◽  
Vol 58 (7) ◽  
pp. 531
Author(s):  
Laura Andrau ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Crystal Structures ◽  
Bond Distance ◽  
Lone Pair ◽  
X Ray ◽  
Ester Derivative ◽  
Bond Interaction ◽  
Derivatives Of ◽  
Electron Demand

Low-temperature X-ray crystal structures were determined on a range of derivatives of 4-thiacyclohexanol 5a of varying electron demand with a view to finding evidence for a through-bond interaction between the sulfur lone pair and the oxygenated substituent. In contrast to earlier suggestions, plots of C–OR bond distance versus pKa (ROH) showed that any interaction between the sulfur and the OR group is unlikely to be of a through-bond origin. Furthermore, unimolecular solvolysis rate measurements on the nosylate ester derivative 5g showed that the sulfur actually retards the reaction slightly in comparison with the corresponding sulfur-free analogue 6.

Synthesis and PMR spectra of vinyl derivatives of 2-hydroxylepidine

1971 ◽  
Vol 7 (6) ◽  
pp. 744-745
Author(s):  
G. G. Skvortsova ◽  
S. M. Tyrina ◽  
V. K. Voronov
Keyword(s):  
Pmr Spectra ◽  
Vinyl Derivatives ◽  
Derivatives Of

ChemInform Abstract: A Convenient Method for the Synthesis of N-Vinyl Derivatives of Nucleobases.

ChemInform ◽  
2010 ◽  
Vol 33 (24) ◽  
pp. no-no
Author(s):  
Renato Dalpozzo ◽  
Antonio De Nino ◽  
Loredana Maiuolo ◽  
Antonio Procopio ◽  
Roberto Romeo ◽  
...  
Keyword(s):  
Convenient Method ◽  
Vinyl Derivatives ◽  
Derivatives Of

Dative behavior of N-heterocyclic carbenes (NHCs) with selenium in Se-NHC compounds

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Munazzah Yaqoob ◽  
Mahvish Abbasi ◽  
Hira Anwar ◽  
Javed Iqbal ◽  
Mohammad Asad ◽  
...  
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Lone Pair ◽  
Heterocyclic Ring ◽  
Heterocyclic Carbenes ◽  
The Other ◽  
Donor Ligands ◽  
Important Research ◽  
Dative Bond ◽  
Back Bonding

Abstract N-heterocyclic carbenes (NHCs) are an eminent class of carbenes having a heterocyclic ring in which a divalent carbon atom is attached directly to a nitrogen atom. In the NHCs, the donation of lone pair is another important research in the dative bonding and not only in NHCs the dative bond plays a functionalized role in the other classes of complex formation like ylidones L → E ← L and carbones L → C ← L. M–NHC bond is L-M sigma-dative bond and NHCs are considered as strong sigma-donor ligands. The clear picture of the M–NHC bond can be better understood by M–NHC pi-interaction. M-L pi interaction is comprised of two steps. One is L → M sigma-donation and M → L π* back bonding. This dative donor nature of NHC and also its behavior in organoselenium is studied through DFT in which it’s optimized structure, bond lengths, molecular vibrations are calculated.

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