scholarly journals The crystal structures of fourN-(4-halophenyl)-4-oxo-4H-chromene-3-carboxamides

2015 ◽  
Vol 71 (1) ◽  
pp. 88-93 ◽  
Author(s):  
Ligia R. Gomes ◽  
John Nicolson Low ◽  
Fernando Cagide ◽  
Fernanda Borges
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Carbonyl Group ◽  
Supramolecular Structure ◽  
Intramolecular Hydrogen Bonding ◽  
Pyrone Ring ◽  
Axis Direction ◽  
Unit Translation ◽  
Intramolecular Hydrogen

FourN-(4-halophenyl)-4-oxo-4H-chromene-3-carboxamides (halo = F, Cl, Br and I),N-(4-fluorophenyl)-4-oxo-4H-chromene-3-carboxamide, C16H10FNO3,N-(4-chlorophenyl)-4-oxo-4H-chromene-3-carboxamide, C16H10ClNO3,N-(4-bromophenyl)-4-oxo-4H-chromene-3-carboxamide, C16H10BrNO3,N-(4-iodophenyl)-4-oxo-4H-chromene-3-carboxamide, C16H10INO3, have been structurally characterized. The molecules are essentially planar and each exhibits ananticonformation with respect to the C—N rotamer of the amide and acisgeometry with respect to the relative positions of the Carom—Carombond of the chromone ring and the carbonyl group of the amide. The structures each exhibit an intramolecular hydrogen-bonding network comprising an N—H...O hydrogen bond between the amide N atom and the O atom of the carbonyl group of the pyrone ring, forming anS(6) ring, and a weak Carom—H...O interaction with the O atom of the carbonyl group of the amide as acceptor, which forms anotherS(6) ring. All four compounds have the same supramolecular structure, consisting ofR22(13) rings that are propagated along thea-axis direction by unit translation. There is π–π stacking involving inversion-related molecules in each structure.

scholarly journals Conformational analysis and intramolecular interactions in monosubstituted phenylboranes and phenylboronic acids

2013 ◽  
Vol 9 ◽  
pp. 1127-1134 ◽  
Author(s):  
Josué M Silla ◽  
Rodrigo A Cormanich ◽  
Roberto Rittner ◽  
Matheus P Freitas
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Conformational Analysis ◽  
Conformational Equilibrium ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Interactions ◽  
Coupling Constant ◽  
Intramolecular Hydrogen ◽  
Phenylboronic Acids ◽  
Electron Donation

A 1 TS J F,H(O) coupling pathway, dictated by a hydrogen bond, in some 2-fluorobenzoic acids has been observed, while such an interaction does not occur in 2-fluorophenol. Thus, this work reports the conformational analysis of 2-fluorophenylboronic acid (1), in order to evaluate a possible intramolecular OH∙∙∙F hydrogen bond in comparison to an nF→pB interaction, which mimics the quantum nF→σ*OH hydrogen bond that would be expected in 2-fluorophenol. 2-Fluorophenylborane (3), which does not experience hydrogen bonding, was used to verify whether nF→pB interaction governs the conformational equilibrium in 1 due to a predominant OH∙∙∙F hydrogen bond or to other effects. A series of 2-X-phenylboranes (X = Cl, Br, NH2, PH2, OH and SH) were further computationally analyzed to search for electron donors to boron, capable of influencing the conformational equilibrium. Overall, the intramolecular OH∙∙∙F hydrogen bond in 1 is quite stabilizing and dictates the 1 h J F,H(O) coupling constant. Moreover, electron donation to the empty p orbital of boron (for noncoplanar BH2 moiety relative to the phenyl ring) is also significantly stabilizing for the NH2 and PH2 derivatives, but not enough to make the corresponding conformers appreciably populated, because of steric effects and the loss of πCC→pB resonance. Thus, the results found earlier for 2-fluorophenol about the lack of intramolecular hydrogen bonding are now corroborated.

Theoretical aspects of the enhancement of metal binding affinity by intramolecular hydrogen bonding and modulating pKavalues

2017 ◽  
Vol 41 (24) ◽  
pp. 15110-15119 ◽  
Author(s):  
Ahmad Motahari ◽  
Alireza Fattahi
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Binding Affinity ◽  
Metal Binding ◽  
Intramolecular Hydrogen Bonding ◽  
Hydrogen Bond Network ◽  
Bond Network ◽  
The Stability ◽  
Intramolecular Hydrogen

The stability balance shows that the hydrogen bond network and modulation of pKavalues can enhance the metal binding affinity.

Two terphenyl-based diol hosts and corresponding solvent inclusions with dimethylformamide and acetonitrile

2015 ◽  
Vol 71 (9) ◽  
pp. 768-775
Author(s):  
Hendrik Klien ◽  
Wilhelm Seichter ◽  
Konstantinos Skobridis ◽  
Edwin Weber
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Solvent Molecule ◽  
Intramolecular Hydrogen Bonding ◽  
Host Lattice ◽  
Solvent Free ◽  
Guest Molecules ◽  
Solvent Molecules ◽  
Intramolecular Hydrogen ◽  
Supramolecular Aggregates

Having reference to an elongated structural modification of 2,2′-bis(hydroxydiphenylmethyl)biphenyl, (I), the two 1,1′:4′,1′′-terphenyl-based diol hosts 2,2′′-bis(hydroxydiphenylmethyl)-1,1′:4′,1′′-terphenyl, C44H34O2, (II), and 2,2′′-bis[hydroxybis(4-methylphenyl)methyl]-1,1′:4′,1′′-terphenyl, C48H42O2, (III), have been synthesized and studied with regard to their crystal structures involving different inclusions,i.e.(II) with dimethylformamide (DMF), C44H34O2·C2H6NO, denoted (IIa), (III) with DMF, C48H42O2·C2H6NO, denoted (IIIa), and (III) with acetonitrile, C48H42O2·CH3CN, denoted (IIIb). In the solvent-free crystals of (II) and (III), the hydroxy H atoms are involved in intramolecular O—H...π hydrogen bonding, with the central arene ring of the terphenyl unit acting as an acceptor. The corresponding crystal structures are stabilized by intermolecular C—H...π contacts. Due to the distinctive acceptor character of the included DMF solvent species in the crystal structures of (IIa) and (IIIa), the guest molecule is coordinated to the hostviaO—H...O=C hydrogen bonding. In both crystal structures, infinite strands composed of alternating host and guest molecules represent the basic supramolecular aggregates. Within a given strand, the O atom of the solvent molecule acts as a bifurcated acceptor. Similar to the solvent-free cases, the hydroxy H atoms in inclusion structure (IIIb) are involved in intramolecular hydrogen bonding, and there is thus a lack of host–guest interaction. As a result, the solvent molecules are accommodated as C—H...N hydrogen-bonded inversion-symmetric dimers in the channel-like voids of the host lattice.

Hydrogen bonding, configuration and conformation of substituted α-oxo oximes and hydrazones

1979 ◽  
Vol 44 (8) ◽  
pp. 2494-2506 ◽  
Author(s):  
Otto Exner ◽  
Jorga Smolíková ◽  
Václav Jehlička ◽  
Ahmad S. Shawali
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Carbonyl Group ◽  
Intramolecular Hydrogen Bond ◽  
Benzene Solution ◽  
Dipole Moments ◽  
H Nmr ◽  
Intramolecular Hydrogen ◽  
Derivatives Of ◽  
Configuration And Conformation

Substituted 2-bromo-1-phenylglyoxal 2-phenylhydrazones IIIa-f exist in tetrachloromethane or benzene solutions prevailingly in E-configuration and in conformation A with an intramolecular hydrogen bond. The latter was evidenced by the N-H valence frequency at 3 290 cm-1 and by 1H NMR shifts with reference to derivatives without a carbonyl group - α-chlorobenzaldehyde phenylhydrazones V. From dipole moments of IIIa-d, measured in benzene solution, the contribution of the hydrogen bond (μH) was evaluated to 17 . 10-30 C m. This quantity is twice larger than in any other reported compound but the direction of the vector is as usual: approximately from H to N. In structurally similar derivatives of hydroxylamine, substituted 2-phenylglyoxylhydroximoyl chlorides IVa-d, no intramolecular hydrogen bond was detected; the dipole moments found were interpreted in terms of the Z-configuration and the prevailing conformation G.

scholarly journals Separation of planar rotamers through intramolecular hydrogen bonding in polysubstituted 5-nitrosopyrimidines

2014 ◽  
Vol 50 (94) ◽  
pp. 14892-14895 ◽  
Author(s):  
L. Čechová ◽  
E. Procházková ◽  
I. Císařová ◽  
M. Dračínský ◽  
Z. Janeba
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bond ◽  
Chemical Species ◽  
Intramolecular Hydrogen Bonding ◽  
Nitroso Group ◽  
Group Orientation ◽  
Intramolecular Hydrogen

Unique isolation of pairs of planar rotamers, planamers, as chemical species differing only in nitroso group orientation, separable through the presence of a single intramolecular hydrogen bond, is reported.

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