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.

scholarly journals Computational evidence for intramolecular hydrogen bonding and nonbonding X···O interactions in 2'-haloflavonols

2012 ◽  
Vol 8 ◽  
pp. 112-117 ◽  
Author(s):  
Tânia A O Fonseca ◽  
Matheus P Freitas ◽  
Rodrigo A Cormanich ◽  
Teodorico C Ramalho ◽  
Cláudio F Tormena ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Quantum Theory ◽  
Intramolecular Hydrogen Bond ◽  
Natural Bond Orbital ◽  
Intramolecular Hydrogen Bonding ◽  
Nbo Analysis ◽  
Conformational Isomerism ◽  
Intramolecular Hydrogen ◽  
Stereoelectronic Interactions

The conformational isomerism and stereoelectronic interactions present in 2'-haloflavonols were computationally analyzed. On the basis of the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis, the conformer stabilities of 2'-haloflavonols were found to be dictated mainly by a C=O···H–O intramolecular hydrogen bond, but an unusual C–F···H–O hydrogen-bond and intramolecular C–X···O nonbonding interactions are also present in such compounds.

scholarly journals THE STUDY OF HYDROGEN BONDING AND RELATED PHENOMENA BY ULTRAVIOLET LIGHT ABSORPTION: PART VI. THE EFFECT OF STERIC INTERACTIONS ON THE INTRAMOLECULAR HYDROGEN BOND IN o-NITROPHENOL

1960 ◽  
Vol 38 (10) ◽  
pp. 1852-1864 ◽  
Author(s):  
J. C. Dearden ◽  
W. F. Forbes
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bond ◽  
Alkyl Substituent ◽  
Intramolecular Hydrogen Bonding ◽  
Vibration Band ◽  
Absorption Bands ◽  
Steric Interactions ◽  
Stretching Vibration ◽  
Intramolecular Hydrogen

Intramolecular hydrogen bonding occurring in o-nitrophenol is discussed with special reference to the effects of the steric interactions on the absorption bands and on the bonding. An alkyl substituent vicinal to the OH group, or a methyl group vicinal to the NO2 group appears to strengthen the intramolecular hydrogen bond in o-nitrophenol. The O—H vibrational stretching frequency in o-nitrophenol appears to be more susceptible to steric than to mesomeric interactions, and a methyl substituent vicinal to the nitro group in o-nitrophenols is found to give rise to a characteristic O—H stretching vibration band. For 6-t-butyl-2-nitrophenol, a special, "protected" hydrogen bond is postulated. In some of the o-nitrophenols, intermolecular hydrogen bonding gives rise to appreciable ultraviolet intensity decreases presumably because of increased steric interactions.

THE STUDY OF HYDROGEN BONDING AND RELATED PHENOMENA BY ULTRAVIOLET LIGHT ABSORPTION: PART V. INTRAMOLECULAR HYDROGEN BONDING IN ANILINES AND PHENOLS

1960 ◽  
Vol 38 (10) ◽  
pp. 1837-1851 ◽  
Author(s):  
J. C. Dearden ◽  
W. F. Forbes
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bond ◽  
Light Absorption ◽  
Intramolecular Hydrogen Bonding ◽  
Electrostatic Model ◽  
Spectral Change ◽  
Substituted Phenols ◽  
Spectral Changes ◽  
Intramolecular Hydrogen

Information concerning intramolecular hydrogen bonding in phenols and anilines can be obtained from ultraviolet spectra by a variety of methods. One method is to note the spectral changes observed between the corresponding o-substituted phenols and anisoles. A second method is to compare the spectral changes between o-substituted phenols or anilines and the corresponding meta isomers. A third method is to note the absence of an appreciable spectral change, on altering the solvent conditions, which may also indicate the formation of an intramolecular hydrogen bond. The conclusions deduced from the three methods confirm previously stated generalizations concerning the nature of the hydrogen bond. One notable exception is that the spectral changes ascribed to the intramolecular hydrogen bond in o-nitrophenol can be explained in terms of an electrostatic model of the hydrogen bond.

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.

THE STUDY OF HYDROGEN BONDING AND RELATED PHENOMENA BY SPECTROSCOPIC METHODS: PART VIII. THE ULTRAVIOLET AND INFRARED SPECTRA OF SOME 2,4-DINITRODIPHENYLAMINES

1964 ◽  
Vol 42 (12) ◽  
pp. 2674-2683 ◽  
Author(s):  
A. Balasubramanian ◽  
J. B. Capindale ◽  
W. F. Forbes
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Spectral Data ◽  
Intramolecular Hydrogen Bond ◽  
Infrared Spectra ◽  
Positive Charge ◽  
Spectroscopic Methods ◽  
Amino Group ◽  
Strong Type ◽  
Intramolecular Hydrogen

The ultraviolet spectra of a number of 2,4-dinitrodiphenylamines suggest that these compounds are generally non-planar in a number of different solvents. The infrared and ultraviolet spectral data in different solvents also suggest that an intramolecular hydrogen bond is present in these molecules, at least in inert solvents. There is evidence that a p-nitro substituent is necessary to increase the positive charge on the amino group sufficiently to permit it to form this fairly strong type of hydrogen bond.

Intra- and inter-molecular hydrogen bonding in diphytanylglycerol phospholipids: an infrared spectroscopic investigation

1990 ◽  
Vol 68 (1) ◽  
pp. 266-273 ◽  
Author(s):  
L. C. Stewart ◽  
M. Kates ◽  
P. W. Yang ◽  
H. H. Mantsch
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Intramolecular Hydrogen Bond ◽  
Membrane Lipids ◽  
Head Group ◽  
Exact Nature ◽  
Oh Groups ◽  
Intramolecular Hydrogen ◽  
Phosphate Groups

A series of diphytanylglycerol phospholipids, i.e., diphytanylglycerol phosphate (PA), diphytanylglycerol phosphoglycerophosphate (PGP), the tri- and tetra-methyl derivatives of PGP, and the 2-deoxyglycerol analogue of PGP (dPGP) were studied by Fourier transform infrared spectroscopy. The use of the "deoxy" and methylated analogues of PGP, as well as that of PA and PGP of varying degrees of ionization, allowed the assignment of characteristic infrared bands associated with the phosphate groups. Analysis of these phosphate bands showed that at neutral pH, each of the two phosphate moieties in PGP is singly ionized, whereas in dPGP the phosphomonoester is doubly ionized. This is a consequence of the marked increase in the pK of one of the P-OH groups on the terminal phosphate of PGP (pK > 11), owing to the formation of an intramolecular hydrogen bond between the head group glycerol hydroxyl and the phosphate groups of PGP. Such an intramolecular hydrogen bond can not be formed by the dPGP analogue, and thus both negative charges in dPGP are located at the terminal phosphomonoester group. The O=P—OH groups of PGP also forms a network of intermolecular hydrogen bonds, the exact nature of which depends on concentration and degree of ionization. The possibility of a complex network of hydrogen bonds within (intramolecular) and between (intermolecular) anionic membrane lipids such as that found in PGP, is consistent with the hypothesis that these lipids function as proton-conducting pathways in membranes.Key words: phospholipids, infrared, hydrogen bonding, phosphatidylglycerophosphate, 2-deoxyphosphatidylglycerophosphate.

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.

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