Interplay between Hydrogen-Bond Formation and Multicenter π-Electron Delocalization: Intramolecular Hydrogen Bonds

2008 ◽  
Vol 112 (42) ◽  
pp. 10689-10696 ◽  
Author(s):  
Pieterjan Lenain ◽  
Marcos Mandado ◽  
Ricardo A. Mosquera ◽  
Patrick Bultinck
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Bond Formation ◽  
Electron Delocalization ◽  
Hydrogen Bond Formation ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen

Large perturbations of long-range nJ(1H,1H) and nJ(1H,19F) by the intramolecular hydrogen bonds in 2-mercaptobenzaldehyde, salicylaldehyde, and some derivatives. Reference structures for intramolecular hydrogen bonds

1993 ◽  
Vol 71 (7) ◽  
pp. 960-967 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
David M. McKinnon ◽  
Perry W. Spevack ◽  
Kerry J. Cox ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Long Range ◽  
Bond Formation ◽  
Coupling Constants ◽  
Hydrogen Bond Formation ◽  
Intramolecular Hydrogen Bonds ◽  
Large Perturbation ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bonded

Precise 1H nuclear magnetic resonance spectral parameters are reported for salicyladehyde and its 3-fluoro and 5-fluoro derivatives in nonpolar solutions. Such data are also given for the 2-mercapto, 2-methylthio, and 2-methoxy derivatives of benzaldehyde. Comparison of the long-range coupling constants in the various compounds and their conformers shows a large perturbation of their magnitudes by hydrogen bond formation. For the salicylaldehyde system, the perturbation is particularly large for couplings involving the aldehyde proton and protons or fluorine nuclei placed ortho to the hydroxyl group. For example, 5Jt (F, CHO) is reduced by about 50%. The perturbation, as expected, is much smaller for coupling constants of nuclei remote from the site of the hydrogen bond. In 2-mercaptobenzaldehyde the long-range coupling constants are also sensitive to hydrogen bond formation, those involving the sulfhydryl proton markedly so compared to the hydroxyl proton in salicylaldehyde. The strength of the [Formula: see text] bond is discussed. It is argued that the reference conformer for the mercapto compound in such a discussion is less easily defined than for salicylaldehyde because [Formula: see text] are similar to [Formula: see text] energies. The experimental data for the CCl4 solutions imply a free energy of formation of the [Formula: see text] bond of 4.8(5) kJ/mol at 300 K. Molecular orbital computations on the four planar conformers of each salicylaldehyde and 2-mercaptobenzaldehyde with the 6-31 G**(5D) basis are reported. For salicylaldehyde, the [Formula: see text] arrangement is taken as the reference conformer, with a computed energy of 25.7 kJ/mol relative to the hydrogen-bonded structure. For 2-mercaptobenzaldehyde, the [Formula: see text] and [Formula: see text] conformers are calculated to be isoenergetic, at 5.1 kJ/mol relative to the hydrogen-bonded conformer. Hence either arrangement serves as a reference structure in computations of the strength of the hydrogen bond. The computations are consistent with the experimental results for solutions of the molecules under discussion. An appendix gives the computed geometries of the eight planar conformers, as well as some atomic charges, allowing a rationalization of the relative energies of the conformers.

Halogen Bonding Organocatalysis Enhanced through Intramolecular Hydrogen Bonds

2022 ◽  
Author(s):  
Asia Marie S Riel ◽  
Daniel Adam Decato ◽  
Jiyu Sun ◽  
Orion Berryman
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Halogen Bond ◽  
Direct Interaction ◽  
Halogen Bonding ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen

Recent results indicate a halogen bond donor is strengthened through direct interaction with a hydrogen bond to the electron-rich belt of the halogen. Here, this Hydrogen Bond enhanced Halogen Bond...

scholarly journals Synthesis of a Conformationally Stable Atropisomeric Pair of Biphenyl Scaffold Containing Additional Stereogenic Centers

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 643 ◽  
Author(s):  
Chi-Tung Yeung ◽  
Wesley Chan ◽  
Wai-Sum Lo ◽  
Ga-Lai Law ◽  
Wing-Tak Wong
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Bond Formation ◽  
Aldol Reaction ◽  
Spatial Arrangement ◽  
Hydroxyl Groups ◽  
Hydrogen Bond Formation ◽  
X Ray ◽  
Stereogenic Centers ◽  
Intramolecular Hydrogen

The synthesis of a new CF3-containing stereogenic atropisomeric pair of ortho-disubstituted biphenyl scaffold is presented. The atropisomers are surprisingly conformationally stable for isolation. X-ray structures show that their stability comes from an intramolecular hydrogen bond formation from their two hydroxyl groups and renders the spatial arrangement of their peripheral CF3 and CH3 groups very different. The synthesized stereogenic scaffold proved to be effective in catalyzing the asymmetric N-nitroso aldol reaction of enamine and nitrosobenzene. Compared to similar scaffolds without CF3 groups, one of our atropisomer exhibits an increase in enantioselectivity in this reaction.

Intramolecular hydrogen bonds: common motifs, probabilities of formation and implications for supramolecular organization

2000 ◽  
Vol 56 (5) ◽  
pp. 849-856 ◽  
Author(s):  
Clair Bilton ◽  
Frank H. Allen ◽  
Gregory P. Shields ◽  
Judith A. K. Howard
Keyword(s):  
Hydrogen Bond ◽  
Bond Formation ◽  
Intermolecular Hydrogen Bond ◽  
The Other ◽  
Supramolecular Organization ◽  
Intermolecular Bond ◽  
Hydrogen Bond Formation ◽  
Ability To Act ◽  
Structural Database ◽  
Intramolecular Hydrogen

A systematic survey of the Cambridge Structural Database (CSD) has identified all intramolecular hydrogen-bonded ring motifs comprising less than 20 atoms with N and O donors and acceptors. The probabilities of formation Pm of the 50 most common motifs, which chiefly comprise five- and six-membered rings, have been derived by considering the number of intramolecular motifs which could possibly form. The most probable motifs (Pm > 85%) are planar conjugated six-membered rings with a propensity for resonance-assisted hydrogen bonding and these form the shortest contacts, whilst saturated six-membered rings typically have Pm < 10%. The influence of intramolecular-motif formation on intermolecular hydrogen-bond formation has been assessed for a planar conjugated model substructure, showing that a donor-H is considerably less likely to form an intermolecular bond if it forms an intramolecular one. On the other hand, the involvement of a carbonyl acceptor in an intramolecular bond does not significantly affect its ability to act as an intermolecular acceptor and thus carbonyl acceptors display a substantially higher inclination for bifurcation if one hydrogen bond is intramolecular.

1H -NMRInvestigations on the Hydrogen Bond Formation between the Tranquilizers Diazepam and Nitrazepam and Some Nucleobases

1978 ◽  
Vol 33 (11-12) ◽  
pp. 870-875 ◽  
Author(s):  
Hans-Helmut Paul ◽  
Helmut Sapper ◽  
Wolfgang Lohmann
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Binding Sites ◽  
Spectroscopic Data ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Bond Formation ◽  
Resonance Spectroscopy ◽  
Hydrogen Bond Formation ◽  
Dimer Model

The formation of hydrogen bonds between the minor tranquilizers diazepam and nitrazepam and a few nucleobases was studied in deuterochloroform solution by means of proton magnetic resonance spectroscopy. The thermodynamic and spectroscopic data of the associations were evaluated on the basis of a dimer model, using the concentration dependent shifts of the protons involved in hydrogen bonds. The interactions of nitrazepam (ΔH0= -10 to -21 k J/mol; ΔG250 - 0.2 to -7.4 kJ/mol) were found to be stronger than those of diazepam (ΔH0 = - 10 to - 13 kJ/mol; ΔG250 = 6.0 to 6.4 k j/mol). The various binding sites of the benzodiazepines for hydrogen bonds are discussed.

Intramolecular hydrogen bonds and the orientation of amino groupsin o-phenylenediamines

1967 ◽  
Vol 45 (19) ◽  
pp. 2135-2141 ◽  
Author(s):  
P. J. Krueger
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Infrared Absorption ◽  
Substituent Effect ◽  
Proton Donor ◽  
Proton Acceptor ◽  
Amino Groups ◽  
Intramolecular Hydrogen Bonds ◽  
Infrared Absorption Spectra ◽  
Intramolecular Hydrogen

The infrared absorption spectra of partially deuterated o-phenylenediamine and 4,5-di-methyl-, 4-methyl-, and 4-chloro-o-phenylenediamine in dilute CCl4 solution show double intramolecular [Formula: see text] hydrogen bonds in which the two NHD groups are equivalent and each group acts as both a proton donor and a proton acceptor. The ring substituent effect on this interaction in these compounds is small. In 4-methoxy-o-phenylenediamine, the amino groups are not equivalent, but double intramolecular hydrogen bonds are still present. In 4-nitro-o-phenylenediamine, only one intramolecular [Formula: see text] hydrogen bond appears to exist. The effect of N-substitution on some of these observations is discussed.

scholarly journals Polarisable Hydrogen Bond Formation and Ionic Interactions in Model Phospholipid Polar Head Molecules

1973 ◽  
Vol 28 (5-6) ◽  
pp. 323-330 ◽  
Author(s):  
Georg Papakostidis ◽  
Georg Zundel
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Phosphoric Acid ◽  
Bond Formation ◽  
Ion Pairs ◽  
Water Soluble ◽  
Ionic Interactions ◽  
Hydrogen Bond Formation ◽  
Continuous Absorption ◽  
Phosphate Groups

The serine phosphoric acid P-methylester (SPM) and the ethanol-amine phosphoric acid P-methylester (EPM) were synthesized as water soluble models for the functional groups of the corresponding phospholipids. Investigations were made of the aqueous solutions of these molecules as a function of deprotonation and protonation. An intramolecular, easily polarisable hydrogen bond occurs in the zwitterion of the SPM. The solutions of different salts of SPM were studied as well as the influence of counter ion pairs. Counterion pairs hardly influence these bonds. At about 50% deprotonation extremely easily polarisable intermolecular bonds form. At about 100% deprotonation of the zwitterion the hydrogen bonds observed are affected by the presence of CO2. The above is indicated by changes of the bands of the carboxylic and phosphate groups, and in particular by a continuous absorption in the infrared spectrum. During protonation of the EPM easily polarisable intermolecular POH+ ... OP hydrogen bonds form at first, but as protonation increases the solutions become acidic, that is, H5O2+ groupings form.

Sign in / Sign up

Export Citation Format

Share Document