Effects of intramolecular hydrogen bonds on intermolecular hydrogen bonding

Spencer, J. N.; Robertson, K. S.; Quick, Edward Edwards

doi:10.1021/j100615a011

Cited by 23 publications

(25 citation statements)

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“…For 2 , our value of K is slightly lower than that of Taft et al , This difference will become less prominent when K is converted to Δ G using the relation Δ G = − RT ln( K ). Spencer et al measured both 2 and 1-OCH 3 using methods very similar to those here . For 2 , their value was lower than both ours and those of Taft et al For 1-OCH 3 , their value was higher than ours.…”

Section: Resultssupporting

confidence: 59%

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Approximating the Strength of the Intramolecular Hydrogen Bond in 2-Fluorophenol and Related Compounds: A New Application of a Classic Technique

et al. 2020

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Fluorinated organic compounds are ubiquitous in the pharmaceutical and agricultural industries. To better discern the mode of action of these compounds, it is critical to understand the strengths of hydrogen bonds involving fluorine. While established techniques can determine these strengths for intermolecular complexes, there is no analogous scheme for intramolecular hydrogen bonds. This work uses 1H nuclear magnetic resonance spectroscopy to measure the strength of intramolecular hydrogen bonds in ortho-substituted phenols. Titration of each phenol with DMSO in CCl4 yields a free energy of binding (ΔG). Subtraction of this value from the ΔG of binding of the standard, 4-fluorophenol, is shown to give the difference in ΔG for the cis and trans isomers of the ortho-substituted phenols. This difference is conventionally taken to be approximately equal to the ΔG of the intramolecular hydrogen bond. These data complement theoretical methods, which yield slightly larger ΔGs. Both theory and experiment point to a weak intramolecular hydrogen bond in 2-fluorophenol. The other 2-X-phenols have stronger hydrogen bonds, following the order F < Cl ≈ Br < OCH3. The methodology developed here can be readily applied to other systems with intramolecular hydrogen bonds.

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Section: Resultssupporting

confidence: 59%

“… a This work. Values in parentheses are one standard deviation of error. b Taft et al (refs , ). c Spencer et al (ref ). d Abraham et al (refs , ). e Abraham et al (ref ). f Laurence and Gal (ref ). g Uses phenol instead of 4-fluorophenol. …”

Section: Resultsmentioning

confidence: 99%

Approximating the Strength of the Intramolecular Hydrogen Bond in 2-Fluorophenol and Related Compounds: A New Application of a Classic Technique

et al. 2020

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“…The reported experimental values for the intramolecular hydrogen bonding in 2-methoxyphenol include 3.3 kcal mol −1 by Spencer et al 59 and a recent gas phase value of 3.2 kcal mol −1 by Varfolomeev et al 60 The enthalpy difference between e2 and e4 (3.4 kcal mol −1 ) is more consistent than the one between e1 and e3 (5.0 kcal mol −1 ) with the aforementioned reported values. This might strongly indicate that ortho methoxyl groups would most likely be positioned in actual equilibrium structures as out-of-plane substituents, in order to minimize steric congestion.…”

Section: -Methoxyphenol 26-dimethoxyphenol and Hesperetinsupporting

confidence: 63%

Computation of the bond dissociation enthalpies and free energies of hydroxylic antioxidants using theab initioHartree–Fock method

Woldu

Mai

2012

Redox Report

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“…The binding energies became more favorable as the number of OH groups was increased (Figure A). Such a trend could be rationalized by cooperative effects arising from the formation of a linear intramolecular H‐bond network between the OH groups (Figure B) . However, the experimental energetic trend shown in Figure A was not reproduced in DFT energy calculations for the linear binding mode (Figure A; see also solid bars in Figure A).…”

Section: Figurementioning

confidence: 98%

Strong Short‐Range Cooperativity in Hydrogen‐Bond Chains

et al. 2017

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Chains of hydrogen bonds such as those found in water and proteins are often presumed to be more stable than the sum of the individual Hbonds.However,the energetics of cooperativity are complicated by solvent effects and the dynamics of intermolecular interactions,m eaning that information on cooperativity typically is derived from theory or indirect structural data. Herein, we present direct measurements of energetic cooperativity in an experimental system in which the geometry and the number of Hbonds in achain were systematically controlled. Strikingly,w ef ound that adding asecond H-bond donor to form achain can almost double the strength of the terminal Hbond, while further extensions have little effect. The experimental observations add weight to computations whichh ave suggested that strong, but shortrange cooperative effects mayo ccur in H-bond chains.Chainsofhydrogenbondsareprevalentstructural motifs in supramolecular and biological systems. Hbonds are widely proposed to exhibit positive cooperativity, [1] which may be manifested by acombination of conformational [1,2] and electronic effects that may make ac hain more stable than the sum of its parts.[3] Such cooperative effects have been shown to influence reactivity, [4] to contribute to the structure,i nteractions,a nd properties of biomolecules and materials, [5] and to facilitate the communication of chemical information.[6] Hbonded water clusters and chains have been isolated in the solid state [7] and studied experimentally in both liquid and gas phases.[8] Although many nanoscale and bulk properties may be influenced by the cooperativity of H-bond networks,itisnot possible to directly quantify interaction energies from structural or vibrational characteristics.I na ddition, discussion of the relative contributions of electrostatics,p olarization, and covalencyi nHbond cooperativity [5b, 9] is further exacerbated by the challenge of considering the influence of the surrounding solvent.Herein, we have employed synthetic molecular balances [10] to directly measure the effect of H-bond-chain length on the strength of H-bonding interactions in solution. At the outset of our investigation we identified the series of phenol, catechol, and pyrogallol ( Figure 1B)a sapertinent model system for examining cooperativity in H-bond chains.Indeed, H-bond chains have previously been proposed to contribute to the supramolecular properties of catechol and pyrogallol derivatives. [3b, 11] We reasoned that the pre-organization and proximity of the intramolecular H-bond donors and acceptors in this series of compounds would minimize conformational entropic effects to allow examination of cooperative electronic influences.I nitially we measured the experimental complexation Gibbs energies of phenol, catechol, and pyrogallol with the strong H-bond acceptor tri-n-butylphosphine oxide using 31 PNMR spectroscopy.T he binding energies became more favorable as the number of OH groups was increased ( Figure 1A). Such atrend could be rationalized by cooperative e...

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Effects of intramolecular hydrogen bonds on intermolecular hydrogen bonding

Cited by 23 publications

References 0 publications

Approximating the Strength of the Intramolecular Hydrogen Bond in 2-Fluorophenol and Related Compounds: A New Application of a Classic Technique

Approximating the Strength of the Intramolecular Hydrogen Bond in 2-Fluorophenol and Related Compounds: A New Application of a Classic Technique

Computation of the bond dissociation enthalpies and free energies of hydroxylic antioxidants using theab initioHartree–Fock method

Strong Short‐Range Cooperativity in Hydrogen‐Bond Chains

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