Synthesis and Structural Investigation of Some Electron-Rich Nitroaromatics

2019 ◽  
Vol 72 (4) ◽  
pp. 311
Author(s):  
Jonathan M. White ◽  
Colin E. Skene ◽  
John Deadman ◽  
Ruwan Epa ◽  
Sarah Foenander ◽  
...  
Keyword(s):  
Nitro Group ◽  
Bond Distance ◽  
Lone Pair ◽  
Crystal Structure Analysis ◽  
Nucleophilic Aromatic Substitution ◽  
Anomeric Effect ◽  
Aromatic Substitution ◽  
Nitrogen Lone Pair ◽  
Lone Pair Electrons ◽  
Electron Donation

2,4-Difluoro-, 2,4,6-trifluoro-, and 2,3,4,6,tetrafluoronitrobenzenes undergo nucleophilic aromatic substitution, once, twice, and three times with a variety of amine substituents with a high degree of regiochemical control to provide a range of electron-rich nitrobenzene derivatives. In these structures the nitro group proves a useful structural probe to reveal the varying extents of electron donation from the varying number of amino substituents onto the nitro group as revealed by accurate low temperature X-ray crystal structure analysis, thus increasing electron donation manifests in a decrease in the Ar–NO2 distance consistent with increased double bond character, while the N–O bond distance increases as the oxygens accept the electron density. The effect of delocalization of the aniline nitrogen lone pair onto the nitro group impacts on the geometry and hybridization of the nitrogen substituent and also impacts on the ability of the nitrogen lone pair electrons to participate in other competing electronic interactions, such as the nN–σ*C–S anomeric effect as demonstrated by the thiazolidine substituted derivatives 3c, 4c, and 6c.

N.M.R. spectra and stereochemistry of the bipyridyls. III. 2,2'-Bipyridyl and dimethyl derivatives, 3,3'- bipyridyl, and 4,4' - bipyridyl

1967 ◽  
Vol 20 (6) ◽  
pp. 1227 ◽  
Author(s):  
TM Spotswood ◽  
CI Tanzer
Keyword(s):  
Hydrogen Bonding ◽  
Electrostatic Field ◽  
Field Effect ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Diamagnetic Anisotropy ◽  
Equal Importance ◽  
Nitrogen Lone Pair ◽  
Lone Pair Electrons ◽  
Derivatives Of

The analysis of the n.m.r, spectra of 2,2?-, 3,3?-, and 4,4?-bipyridyl and three dimethyl-2,2?-bipyridyls is reported and the factors determining the relative chemical shifts of the ring protons and methyl groups in several solvents are discussed. The diamagnetic anisotropy of the neighbouring ring and electrostatic field effect of the nitrogen lone pair electrons are shown to be of roughly equal importance for derivatives of 2,2?-bipyridyl except in hydrogen bonding solvents. Attenuation of the electrostatic field effect in polar, and particularly in hydrogen bonding solvents, is established for 4- picoline, and for the bipyridyls, and this effect is responsible for striking changes in the spectrum of 2,2?-bipyridyl in hydrogen bonding solvents. An approximate interplanar angle of 58� is derived for 3,3?- dimethyl-2,2?-bipyridyl, and 2,2?-bipyridyl and its 4,4?- and 5,5?- dimethyl derivatives appear to be trans coplanar in all solvents. 3,3?- Bipyridyl and 4,4?-bipyridyl are probably highly twisted in all solvents, or alternatively, behave as essentially free rotors. The predicted conformations are in good agreement with the electronic spectral data.

Molecular Complexes of Cyclophanes, Part XVII Charge-Transfer Complexes of [2.2]- and [2.2.2]Paracyclophane-carbamates with π-Acceptors

1987 ◽  
Vol 42 (9) ◽  
pp. 1147-1152 ◽  
Author(s):  
Aboul-fetouh E. Mourad ◽  
Verena Lehne
Keyword(s):  
Charge Transfer ◽  
Functional Group ◽  
Lone Pair ◽  
Molecular Complexes ◽  
Charge Transfer Complexes ◽  
Electronic Interactions ◽  
H Nmr ◽  
Ct Complex ◽  
Nitrogen Lone Pair ◽  
Lone Pair Electrons

Charge-transfer (CT) complexation between some [2.2]- and [2.2.2]paracyclophane-carbamates as donors with 2,3-dichloro-5.6-dicyanobenzoquinone (DDO ) as well as tetracyanoethylene (TCNE) as π-acceptors has been evidenced by VIS. 1H NMR and IR spectroscopy. The site of interaction in the two different donor systems was determined. The results reveal no contribution of the nitrogen lone pair electrons of the carbamate functional group in the CT complexation. and the interaction is mainly of π-π* type. In addition, the existence of the transannular electronic interactions in [2.2]paracyclophane derivatives is responsible for CT complex formation.

Elektronendichte und chemische Verschiebung der Styryldiazin- und Diazaphenanthrenprotonen / Electrondensity and Proton Chemical Shift of Styryldiazines and Diazaphenanthrenes

1972 ◽  
Vol 27 (2) ◽  
pp. 310-319
Author(s):  
H.-H. Perkampus ◽  
Th. Bluhm ◽  
J. Knop
Keyword(s):  
Ring Current ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Current Effect ◽  
Electron Densities ◽  
Paramagnetic Effect ◽  
Nitrogen Lone Pair ◽  
Chemische Verschiebung ◽  
Lone Pair Electrons ◽  
Proton Chemical Shifts

AbstractProton chemical shifts in styryldiazines and diazaphenanthrenes linearly correlate with SCF-π-electron densities of the attached carbon atom and with the electron densities of the hydrogen atom (calculated by the CNDO/2 method). The observed deviations from linearity are discussed in terms of ring current effect, steric effects and the paramagnetic effect of the nitrogen lone pair electrons. An appreciable weakening of ring current is found for diazaphenanthrenes with two adjacent N-atoms. Under the same condition the paramagnetic effect on ortho-hydrogens is increased.

Experimental Electron Density Study of NaH2PO4 at 30 K

1998 ◽  
Vol 54 (1) ◽  
pp. 29-34 ◽  
Author(s):  
M. Ichikawa ◽  
T. Gustafsson ◽  
I. Olovsson
Keyword(s):  
Electron Density ◽  
Bond Distance ◽  
Lone Pair ◽  
Peak Height ◽  
Dihydrogen Phosphate ◽  
Sodium Dihydrogen Phosphate ◽  
Deformation Density ◽  
Density Peaks ◽  
Deformation Electron Density ◽  
Lone Pair Electrons

The deformation electron density of sodium dihydrogen phosphate, NaH2PO4, at 30 K has been studied as a reference for the electron-density characteristics of hydrogen-bonded ferroelectrics containing phosphate ions. Clear peaks of deformation electron density (0.3–0.6 e Å−3) are seen in the middle of each P—O bond and electron deficiency (−0.2 to −0.4 e Å−3) on the opposite side of each P—O bond peak. The peak height is higher and the peak shape is more distinct in P—O bonds than in P—O(H) bonds as a whole; the distribution of deformation density in the region of lone-pair electrons is more diffuse. The O—H...O bond deformation-density peaks of around 0.2 e Å−3 appear in the middle of the O—H bond, followed by a deeper electron depletion of around −0.4 e Å−3 on the H...O contract, just outside the H atom. The effective charges, defined as the integral of the deformation electron density, have the following values: around +0.2 for Na, +1.8 for P, −0.8 for O and +0.6 for H. The correlation of the deformation-density peaks and the depth of the negative peak of the H atom with the hydrogen-bond distance are discussed.

The lattice energy of S -triazine

1968 ◽  
Vol 304 (1479) ◽  
pp. 501-512 ◽  
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Lone Pair ◽  
Lattice Energy ◽  
Pressure Measurements ◽  
Cell Dimensions ◽  
Repulsive Potentials ◽  
Probable Effect ◽  
Nitrogen Lone Pair ◽  
Lone Pair Electrons

The contributions of the dispersive and repulsive potentials to the lattice energy of S -triazine are calculated on the basis of bond-bond and atom-atom interactions respectively. The cell dimensions obtained by minimizing the energy agree with the experimental data to within 4% and the heat of sublimation derived from the vapour pressure measurements is quite close to the calculated lattice energy. The probable effect of the electrostatic forces is dis­cussed and found to be of only marginal importance in determining the crystal structure. No evidence is found for anomalously large repulsions by the nitrogen-lone pair electrons.

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