SPECTROSCOPIC STUDIES OF ALCOHOLS: V. INTRAMOLECULAR HYDROGEN BONDS IN 2-CYANOETHANOL AND IN SOME NITROALCOHOLS

1965 ◽  
Vol 43 (10) ◽  
pp. 2888-2895 ◽  
Author(s):  
P. J. Krueger ◽  
H. D. Mettee
Keyword(s):  
Hydrogen Bonds ◽  
Spectroscopic Studies ◽  
Enthalpy Change ◽  
Kcal Mole ◽  
Gauche Conformation ◽  
Trans Form ◽  
Trans Conformer ◽  
Enthalpy Difference ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bonded

The enthalpy difference between the trans and the intramolecularly hydrogen bonded gauche conformation of 2-cyanoethanol in dilute CCl4 solution is shown to be −0.14 ± 0.03 kcal/mole from the temperature dependence of the fundamental OH stretching bands. At higher concentrations cyclic dimers with double OH … O bonds form. The enthalpy change on dimerization is −6.1 ± 0.3 kcal/mole. A small percentage of dimers with acylic OH … O bonds are also present, but these are thermodynamically less stable than the cyclic dimers.Intramolecular hydrogen bonds are found between OH and NO2 groups in some 2-nitro-alcohols, leading to stabilization of the gauche form with respect to the trans form. For 2-nitroethanol the trans conformer is in equilibrium with two intramolecularly hydrogen bonded conformers (ΔH = −0.40 ± 0.10 and −0.71 ± 0.09 kcal/mole respectively). 2,2-Dinitro-propanol and 2-methyl-2-nitro-1,3-propanediol show complex νOH bands due to trans and intramolecularly hydrogen bonded gauche conformers. 2,2,2-Trinitroethanol has a relatively narrow symmetrical OH peak at temperatures up to 55 °C which is assigned to the exclusively populated intramolecularly hydrogen bonded conformation.

Tuning the cis/trans Conformer Ratio of Xaa-Pro Amide Bonds by Intramolecular Hydrogen Bonds: The Effect on PPII Helix Stability

2010 ◽  
Vol 49 (36) ◽  
pp. 6324-6327 ◽  
Author(s):  
Michael Kuemin ◽  
Yvonne A. Nagel ◽  
Sabine Schweizer ◽  
Fabien W. Monnard ◽  
Christian Ochsenfeld ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Intramolecular Hydrogen Bonds ◽  
Amide Bonds ◽  
Trans Conformer ◽  
Helix Stability ◽  
Intramolecular Hydrogen

SPECTROSCOPIC STUDIES OF ALCOHOLS: III. FUNDAMENTAL OH STRETCHING BANDS OF 2,2-DI- AND 2,2,2-TRI-HALOETHANOLS

1964 ◽  
Vol 42 (2) ◽  
pp. 340-346 ◽  
Author(s):  
P. J. Krueger ◽  
H. D. Mettee
Keyword(s):  
Spectroscopic Studies ◽  
Kcal Mole ◽  
Temperature Dependent ◽  
Hydrogen Bond Interaction ◽  
Constrained System ◽  
Trans Conformer ◽  
Bond Polarizability ◽  
Inductive Effects ◽  
Geometrically Constrained ◽  
Bond Polarization

The OH stretching region was examined for the compounds F3CCH2OH, Cl2CHCH2OH, Cl3CCH2OH, and Br3CCH2OH in dilute CCl4 solution. The first two compounds exhibit temperature-dependent band asymmetry which is due to trans–gauche equilibria arising from rotation about the C—O bond, with relatively small populations in the trans forms. Enthalpy differences of 3.3 and 2.4 kcal/mole between the conformers were obtained for these two compounds respectively. Although symmetrical at lower temperatures, the band for Cl3CCH2OH shows the presence of a small amount of the trans conformer at temperatures above 45 °C. These results are discussed in terms of intramolecular OH … X hydrogen bond interaction, inductive effects, non-bonded interactions, O—H bond polarization, C—X bond polarizability, and the size of the halogen atoms in a geometrically constrained system.

NUCLEAR SHIELDING PARAMETERS FOR PROTONS IN HYDROGEN BONDS: II. CORRELATION OF CHEMICAL SHIFTS IN INTRAMOLECULAR HYDROGEN BONDS WITH INFRARED STRETCHING FREQUENCIES

1960 ◽  
Vol 38 (8) ◽  
pp. 1249-1254 ◽  
Author(s):  
L. W. Reeves ◽  
E. A. Allan ◽  
K. O. Strømme
Keyword(s):  
Hydrogen Bond ◽  
Chemical Shift ◽  
Hydrogen Bonds ◽  
Infinite Dilution ◽  
Chemical Shifts ◽  
Intramolecular Hydrogen Bonds ◽  
A Value ◽  
Nuclear Shielding ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bonded

Nuclear shielding parameters have been obtained for 24 intramolecularly hydrogen-bonded phenols and naphthols. The shielding parameters are corrected for large diamagnetic anisotropies and a value ΔσOH obtained which represents the change in shielding parameter in parts per million with reference to the infinite dilution chemical shift of phenol, α-naphthol, or β-naphthol. These values of ΔσOH are approximately proportional to the change ΔvOH in the OH stretching frequency on formation of the hydrogen bond.

SPECTROSCOPIC STUDIES OF ALCOHOLS: II. THE CONFORMATION OF 2-HALOETHANOLS IN CARBON TETRACHLORIDE SOLUTION

1964 ◽  
Vol 42 (2) ◽  
pp. 326-339 ◽  
Author(s):  
P. J. Krueger ◽  
H. D. Mettee
Keyword(s):  
Carbon Tetrachloride ◽  
Equilibrium Constants ◽  
Spectroscopic Studies ◽  
Kcal Mole ◽  
Band Shift ◽  
Carbon Tetrachloride Solution ◽  
Hydrogen Bond Interactions ◽  
Conformational Equilibria ◽  
Intramolecular Hydrogen ◽  
Conformational Free Energy

Of the five conformers predicted for 2-haloethanols, only two (halogen and OH trans and gauche) can be positively identified by high resolution infrared spectroscopy. From the temperature dependence of the relative intensities of the fundamental OH stretching bands of the trans and gauche forms of the compounds XCH2CH2OH2 where X = F, Cl, Br, and I, the gauche conformers are shown to be energetically favored in dilute carbon tetrachloride solution, with enthalpy differences between the two conformers of 2.07 ± 0.53, 1.20 ± 0.09, 1.25 ± 0.08, and 0.81 ± 0.09 kcal/mole respectively. Equilibrium constants and the conformational free energy and entropy differences are reported. Inter- and intra-molecular OH … X hydrogen-bond interactions are found to be similar in that the enthalpy increases in the order X = I < Br < Cl < F, and is linearly related to a decrease in the fundamental OH band shift, in contrast to the Badger–Bauer relationship. The molecular and thermodynamic factors governing conformational equilibria involving intramolecular hydrogen bonds are discussed.

Hydrogen-Bonded Networks Featuring Yttrium(III) Complexes of N,N’-Dimethylurea (DMU): Preparation and Characterization of [Y(DMU)6][YCl6] and [Y(NO3)3(DMU)3]

2005 ◽  
Vol 60 (4) ◽  
pp. 363-372 ◽  
Author(s):  
Athanassios K. Boudalis ◽  
Vassilios Nastopoulos ◽  
Catherine P. Raptopoulou ◽  
Aris Terzis ◽  
Spyros P. Perlepes
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Single Crystal ◽  
Crystal Engineering ◽  
Coordination Complexes ◽  
3D Network ◽  
3D Architecture ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bonded

In order to examine the possibility of using yttrium(III) in the crystal engineering of hydrogenbonded coordination complexes and to compare the molecular and supramolecular YIII/Cl3 or NO3-/DMU chemistry with the already well-developed LnIII/Cl− or NO3−/DMU chemistry (LnIII = lanthanide, DMU = N,N’-dimethylurea), compounds [Y(DMU)6][YCl6] (1) and [Y(NO3)3(DMU)3] (2) have been prepared. The structures of both compounds have been determined by single-crystal Xray diffraction. The structure of 1 consists of octahedral [Y(DMU)6]3+ and [YCl6]3− ions. The YIII ion in 2 is nine-coordinate and ligation is provided by three O-bonded DMU ligands and three bidentate chelating nitrato groups; the coordination polyhedron about the metal can be viewed as a distorted, monocapped square antiprism. The [Y(DMU)6]3+ cations and [YCl6]3− anions self-assemble to form a hydrogen-bonded 3D architecture in 1. Most of the hydrogen-bonding functionalities on the components of 2 create also a 3D network. Two motifs of interionic/intramolecular hydrogen-bonds have been observed: N-H···Cl in 1 and N-H···O(NO3−) in 2. The IR data are discussed in terms of the nature of bonding and the structures of the two complexes

SPECTROSCOPIC STUDIES OF ALCOHOLS: VI. INTRAMOLECULAR HYDROGEN BONDS IN ETHANOLAMINE AND ITS O- AND N-METHYL DERIVATIVES

1965 ◽  
Vol 43 (11) ◽  
pp. 2970-2977 ◽  
Author(s):  
P. J. Krueger ◽  
H. D. Mettee
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Temperature Dependence ◽  
Spectroscopic Studies ◽  
Intramolecular Hydrogen Bonds ◽  
Distinct Band ◽  
Conformational Equilibria ◽  
Methyl Derivatives ◽  
Intramolecular Hydrogen

The competitive intramolecular [Formula: see text] hydrogen bonding in ethanolamine and N-methylethanolamine has been studied in dilute C2Cl4 solution by means of the temperature dependence of the fundamental OH and NH stretching bands. Of the three conformers identified for each of these compounds, the least stable shows a distinct band which is assigned to a "terminal" OH group involved in an intramolecular [Formula: see text] hydrogen bond. Enthalpy differences between conformers are reported and discussed, and compared with those found for the conformational equilibria in 2-methoxyethylamine and N,N-dimethyl-ethanolamine.

Intramolecular hydrogen bonds in ethylenediamines and otheraliphatic diamines

1967 ◽  
Vol 45 (19) ◽  
pp. 2143-2149 ◽  
Author(s):  
P. J. Krueger
Keyword(s):  
Hydrogen Bonds ◽  
Chain Length ◽  
Band Intensity ◽  
Intramolecular Hydrogen Bonds ◽  
Intensity Measurements ◽  
Methylene Chain ◽  
Aliphatic Diamines ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bonded

The fundamental NH stretching bands of 22 aliphatic diamines have been investigated in dilute C2Cl4 solution.N,N′-Dimethyl-1,3-propanediamine and N,N′-dimethyl- and N,N,N′-trimethyl-ethylenediamine exist predominantly in an intramolecularly hydrogen bonded conformation. Such bonding also exists in N-methyl- and N,N -dimethyl-ethylenediamine, in N-methyl- and N,N-dimethyl-1,3-propanediamine, and in amines of the type H2N(CH2-CH2NH)xCH2CH2NH2. For all of the diamines investigated, intramolecular NH···N bonding disappears sharply when the intervening methylene chain length exceeds three units. Integrated band intensity measurements for primary aliphatic diamines H2N(CH2)nNH2 over the range n = 2–12 suggest that intramolecular hydrogen bonds may also play an important role in the conformation of ethylenediamine and 1,3-diaminopropane.

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.

Tuning the cis/trans Conformer Ratio of Xaa-Pro Amide Bonds by Intramolecular Hydrogen Bonds: The Effect on PPII Helix Stability

2010 ◽  
Vol 122 (36) ◽  
pp. 6468-6471 ◽  
Author(s):  
Michael Kuemin ◽  
Yvonne A. Nagel ◽  
Sabine Schweizer ◽  
Fabien W. Monnard ◽  
Christian Ochsenfeld ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Intramolecular Hydrogen Bonds ◽  
Amide Bonds ◽  
Trans Conformer ◽  
Helix Stability ◽  
Intramolecular Hydrogen
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