Intramolecular OH...pi Interaction. II. The Molecular Structure and Conformation of 4-Pentyn-1-ol.

Trætteberg, M.; Bakken, P.; Seip, Ragnhild; Lüttke, Wolfgang; Knieriem, Burkhard; Sørensen, Georg; Khan, S. I.; Vilkov, L. V.; Rypdal, Kristian

doi:10.3891/acta.chem.scand.42a-0584

Cited by 8 publications

(17 citation statements)

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“…There is no IHB between the two OH groups . In contradiction with previous GED and IR spectroscopic work, two conformers, +sc,+sc,ap and ap,+sc,+ap , neither of which is hydrogen‐bonded, were assigned in the MW spectra of 4‐pentyn‐1‐ol, 4e . QM calculations identify five conformers with relatively low energies, the preponderant conformer assigned, +sc,+sc,ap , being the overall minimum .…”

Section: Discussioncontrasting

confidence: 70%

“…QM calculations identify five conformers with relatively low energies, the preponderant conformer assigned, +sc,+sc,ap , being the overall minimum . The other three, which were not assigned, include the + sc,−sc,+sc conformer, previously believed to be an important hydrogen‐bonded form …”

Section: Discussionmentioning

confidence: 99%

“…A recent review drew attention to the importance of unconventional, weak hydrogen bonds, CH/ n , CH/π and XH/π (X = O, S, Se), in determining the conformations of organic compounds and bioconjugates . Early infrared (IR) spectroscopic studies of small unsaturated alcohols are confirmed by work which in many cases combines IR and/or microwave (MW) spectroscopy, and gas electron diffraction (GED) measurements and photoelectron spectroscopy, with ab initio calculations, to identify the preferred conformers. These studies of the conformational equilibria show them to be dominated by OH/π interactions, and the proximity of putative donors and acceptors is frequently taken as demonstrating that intramolecular hydrogen bonding (IHB) occurs.…”

Section: Introductionmentioning

confidence: 99%

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¹H NMR study of the hetero‐association of unsaturated alcohols with pyridine

Lomas

2011

J of Physical Organic Chem

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The 1H NMR titration method is used to investigate the association of some unsaturated alcohols with pyridine in benzene. The association constant for allyl alcohol (2‐propen‐1‐ol) is slightly higher than for alkanols, but putting one methylene group between the OH and vinyl group completely eliminates this enhancement. In alkynols both the OH and ≡CH protons associate with pyridine. Here, the effects of chain‐lengthening on the association constant are irregular. Values for alkynols and some alcohols with hetero‐atom substituents are lower than expected on the basis of a Taft polar constant (σ*) correlation of alkanol association constants and of a correlation with the pKa’s of the corresponding carboxylic acids. It is suggested that stabilization of the ground state by OH/π interactions is responsible for these low association constants. Small increases in the NMR shifts of the OH protons in the 3‐carbon and 4‐carbon alkenols and alkynols can also be attributed to OH/π interactions, but the 5‐carbon analogues have shifts as low as alkanols. Copyright © 2011 John Wiley & Sons, Ltd.

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Section: Discussioncontrasting

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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¹H NMR study of the hetero‐association of unsaturated alcohols with pyridine

Lomas

2011

J of Physical Organic Chem

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“…The infrared spectra of 4‐pentyn‐1‐ol, 4e , show absorptions corresponding to free and intramolecular hydrogen‐bonded OH groups . In the same way as for 4‐penten‐1‐ol, 3e , the predominant conformer of 4e according to the GED results, +sc , −sc , +sc , has the OH group and the C ≡ C bond close enough for OH/π interactions .…”

Section: Resultsmentioning

confidence: 58%

GIAO/DFT calculations of relative conformer energies and ¹H NMR shifts of unsaturated alcohols in benzene

Lomas

Maurel

2011

J of Physical Organic Chem

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Density functional theory calculations were performed on alkenols and alkynols at the PBE1PBE/6‐311 + G(d,p) level with the inclusion of solvent (benzene) effects by the integral‐equation‐formalism polarizable continuum model (IEFPCM). For the smaller molecules, conformers in which the OH group is in the vicinity of the double or triple bond are preferred, but this preference falls as the alkyl chain is lengthened. The solvent effect on the relative Gibbs energies of different conformers is irregular, and in only two cases, 3‐buten‐1‐ol and 3‐butyn‐1‐ol, is there marked levelling. Gauge‐including atomic orbital calculations, based on the PBE1PBE/6‐311 + G(d,p) geometries but using a larger basis set, cc‐pVTZ, give nuclear magnetic resonance shifts for all the protons in each conformer. Overall shifts are calculated by weighing these according to the conformer population. Calculated values are well correlated with experimental data from high‐dilution spectra in the same solvent, ranging from about 0.4 to 5.8 ppm, with a slope of 1.09 ± 0.01. Calculations on some alcohols with hetero‐atom substituents confirm that these also prefer gauche (synclinal) conformers in the gas phase, with a less marked preference in benzene. The nuclear magnetic resonance shifts, however, are calculated to be on average over 0.8 ppm higher than observed. Copyright © 2011 John Wiley & Sons, Ltd.

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“…Although neither PE nor PP has an oxygen available to form an OH‚‚‚O intramolecular hydrogen bond, the aromatic ring presents a hydrogen bond accepting site as shown previously. 8,9,27 More traditional OH‚ ‚‚O intramolecular hydrogen bonds are possible for phenoxy alcohols. The relative stabilities, ∆G°, are given in Table 2.…”

Section: Resultsmentioning

confidence: 99%

Intramolecular versus Intermolecular Hydrogen Bonding in the Adsorption of Aromatic Alcohols onto an Acrylic Ester Sorbent

et al. 2000

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Intramolecular hydrogen bonds influence intermolecular binding in adsorption and molecular recognition, but the interplay between intra- and intermolecular hydrogen bonding is poorly understood. In this study, a series of four aromatic alcohols, 2-phenylethanol, 3-phenyl-1-propanol, 2-phenoxyethanol, and 3-phenoxy-1-propanol, are examined to determine the effect of intramolecular hydrogen bond formation on the binding to ethyl propionate (EP), an analogue of an acrylic ester separation resin. A combination of infrared spectroscopy, molecular modeling, and ab initio calculations are used to investigate the conformational preferences of the alcohols and the alcohol:EP complexes in hexane. Without EP, 2-phenylethanol and 2-phenoxyethanol prefer intramolecularly hydrogen-bonded conformations, whereas 3-phenyl-1-propanol overwhelmingly favors a conformer without an intramolecular hydrogen bond. For 3-phenoxy-1-propanol, there is a smaller preference for conformers without an intramolecular hydrogen bond. These results agree qualitatively with the experimentally measured IR spectra. The conformational preferences are explained by examining the energy components of low-energy conformers. Electrostatic interactions favor the intramolecularly hydrogen-bonded species, whereas the dihedral energy term and entropic term favor conformers without an intramolecular hydrogen bond. The balance determines the most stable conformer. The calculations predict that all four alcohols bind EP weakly compared with para-methoxyphenol. This ranking is in good agreement with experimental adsorption measurements. The small calculated ΔG° values of ≈ −0.9 to −2.4 kJ/mol for the alcohols is explained in terms of hydrogen bond donating ability, entropy, and the competition between inter- and intramolecular hydrogen bonds.

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Intramolecular OH...pi Interaction. II. The Molecular Structure and Conformation of 4-Pentyn-1-ol.

Cited by 8 publications

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¹H NMR study of the hetero‐association of unsaturated alcohols with pyridine

¹H NMR study of the hetero‐association of unsaturated alcohols with pyridine

GIAO/DFT calculations of relative conformer energies and ¹H NMR shifts of unsaturated alcohols in benzene

Intramolecular versus Intermolecular Hydrogen Bonding in the Adsorption of Aromatic Alcohols onto an Acrylic Ester Sorbent

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Intramolecular OH...pi Interaction. II. The Molecular Structure and Conformation of 4-Pentyn-1-ol.

Cited by 8 publications

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1H NMR study of the hetero‐association of unsaturated alcohols with pyridine

1H NMR study of the hetero‐association of unsaturated alcohols with pyridine

GIAO/DFT calculations of relative conformer energies and 1H NMR shifts of unsaturated alcohols in benzene

Intramolecular versus Intermolecular Hydrogen Bonding in the Adsorption of Aromatic Alcohols onto an Acrylic Ester Sorbent

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¹H NMR study of the hetero‐association of unsaturated alcohols with pyridine

¹H NMR study of the hetero‐association of unsaturated alcohols with pyridine

GIAO/DFT calculations of relative conformer energies and ¹H NMR shifts of unsaturated alcohols in benzene