Redshift or Adduct Stabilization—A Computational Study of Hydrogen Bonding in Adducts of Protonated Carboxylic Acids

Olesen, Solveig Gaarn; Hammerum, Steen

doi:10.1255/ejms.970

Cited by 7 publications

(16 citation statements)

References 57 publications

(50 reference statements)

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“…Bonding in the better stabilized adducts is apparently stronger than normally encountered in the hydrogen-bonded systems considered by Koch and Popelier, considering that application of their criteria would suggest almost covalent bonding in a number of adducts, as the Laplacians of the electron density at the bond critical point of the hydrogen bonds have negative values (Table ). Figure illustrates that the electron density appears to be correlated to the adduct stabilization, as also observed for other hydrogen-bonded adducts. ,, …”

Section: The Formation Of Hydrogen Bonds To Alkyl Radicalssupporting

confidence: 62%

Alkyl Radicals as Hydrogen Bond Acceptors: Computational Evidence

Hammerum

2009

J. Am. Chem. Soc.

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Spectroscopic, energetic and structural information obtained by DFT and G3-type computational studies demonstrates that charged proton donors can form moderately strong hydrogen bonds to simple alkyl radicals. The presence of these bonds stabilizes the adducts and modifies their structure, and gives rise to pronounced shifts of IR stretching frequencies and to increased absorption intensities. The hydrogen bond acceptor properties of alkyl radicals equal those of many conventional acceptors, e.g., the bond length changes and IR red-shifts suggest that tert-butyl radicals are slightly better acceptors than formaldehyde molecules, while propyl radicals are as good as H(2)O. The hydrogen bond strength appears to depend on the proton affinity of the proton donor and on the ionization energy of the acceptor alkyl radical, not on the donor-acceptor proton affinity difference, reflecting that the charge-transfer aspects of hydrogen bonding are particularly conspicuous when the acceptor polarity and basicity is low.

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Section: The Formation Of Hydrogen Bonds To Alkyl Radicalssupporting

confidence: 62%

Alkyl Radicals as Hydrogen Bond Acceptors: Computational Evidence

Hammerum

2009

J. Am. Chem. Soc.

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“…The latter band has been studied at length with isotopomer selectivity and double resonance methods and is due to the OH stretching fundamentals of the embedded hydronium ion in the 4H ·D 2 (so-called “Eigen”) ion. We remark that this overall behavior, where the bands derived from the OH stretches bound to the flanking water molecules and that to the tag evolve in opposite directions with increasing tag binding energy, is the spectroscopic manifestation of H-bond anticooperativity. − , …”

Section: Resultsmentioning

confidence: 88%

“…We remark that this overall behavior, where the bands derived from the OH stretches bound to the flanking water molecules and that to the tag evolve in opposite directions with increasing tag binding energy, is the spectroscopic manifestation of H-bond anticooperativity. [31][32][33][34]37 An important trend revealed by the survey in Figure 3 is the fact that the low energy bands do not simply blue shift, as might be expected from the systematic red shifts of the sharper a 3 bands of the 3H OH group bound to the tags. Instead, a feature in the location of the dominant peak in the 3H spectrum (a 8 ) remains essentially fixed in energy as the intensity profile shifts onto other peaks that lie higher in energy (as shown by the red arrows in Figure 3, which indicate a blueshift of the position for the centroid of the intensity in the region between 1600 and 3000 cm −1 ).…”

Section: Resultsmentioning

confidence: 99%

Disentangling the Complex Vibrational Mechanics of the Protonated Water Trimer by Rational Control of Its Hydrogen Bonds

et al. 2019

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The vibrational spectrum of the protonated water trimer, H + (H 2 O) 3 , is surprisingly complex, with many strong features in the expected region of the fundamentals associated with two H-bonded OH groups on the H 3 O + core ion. Here we follow how the bands in this region of the spectrum evolve when the energies of the fundamentals in the Hbonded OH stretches are systematically increased by the attachment of increasingly strongly bound "tag" molecules (He, Ar, D 2 , N 2 , CO, and H 2 O) to the free OH position on the hydronium core ion of H + (H 2 O) 3 , as well as by replacement of the hydrogen atom in the nonbonded OH group on hydronium with methyl and ethyl groups. This allows for the incremental transformation of the complex band pattern observed in H + (H 2 O) 3 into that of the "Eigen" structure of the protonated water tetramer. Differences among the trajectories of the various bands provide an empirical way to disentangle features primarily due to the displacements of the OH stretches bound to the hydronium core from those arising from anharmonic coupling to states involving one or more quanta in lower frequency modes. The latter are found to be dramatically enhanced when the nominal frequencies of the intermolecular OH stretching modes approach those of the intramolecular bends of the H 3 O + and H 2 O constituents in both H and D isotopologues.

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“…In particular, the energetic consequences of the ionic interactions and the hydrogen bonding cannot be determined separately, but the former probably accounts for the lion’s share in the present systems. It has been observed previously that ionic interactions in general influence the stabilization of charged adducts to such an extent that it is not a particularly good measure of the strength of hydrogen bonds …”

Section: Intermolecular Hydrogen Bondsmentioning

confidence: 98%

“…It has been observed previously that ionic interactions in general influence the stabilization of charged adducts to such an extent that it is not a particularly good measure of the strength of hydrogen bonds. 28…”

Section: Intermolecular Hydrogen Bondsmentioning

confidence: 99%

Hydrogen Bonding to Alkanes: Computational Evidence

Olesen

Hammerum

2009

J. Phys. Chem. A

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The structural, vibrational, and energetic properties of adducts of alkanes and strong cationic proton donors were studied with composite ab initio calculations. Hydrogen bonding in D-H(+)...H-alkyl adducts contributes to a significant degree to the interactions between the two components, which is substantiated by NBO and AIM results. The hydrogen bonds manifest themselves in the same manner as conventional hydrogen bonds, D-H bond elongation, D-H vibrational stretching frequency red shift and intensity increase, and adduct stabilization. The alkane adducts also exhibit elongation of the C-H bonds involved and a concurrent red shift, which is rationalized in terms of charge-transfer interactions that cause simultaneous weakening of both the O-H and C-H bonds. Like other dihydrogen-bonded adducts, the adducts possess a bent structure and asymmetric bifurcated hydrogen bonds. The hydrogen bonds are stronger in adducts of isobutane and in adducts of stronger acids. Intramolecular hydrogen bonding in protonated long-chain alcohols manifests itself in the same manner as intermolecular hydrogen bonding and can be equally strong.

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Redshift or Adduct Stabilization—A Computational Study of Hydrogen Bonding in Adducts of Protonated Carboxylic Acids

Cited by 7 publications

References 57 publications

Alkyl Radicals as Hydrogen Bond Acceptors: Computational Evidence

Alkyl Radicals as Hydrogen Bond Acceptors: Computational Evidence

Disentangling the Complex Vibrational Mechanics of the Protonated Water Trimer by Rational Control of Its Hydrogen Bonds

Hydrogen Bonding to Alkanes: Computational Evidence

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