Evidence for resonance-assisted hydrogen bonding from crystal-structure correlations on the enol form of the .beta.-diketone fragment

Gilli, Gastone; Bellucci, F.; Ferretti, Valeria; Bertolasi, Valerio

doi:10.1021/ja00185a035

Cited by 1,100 publications

(889 citation statements)

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“…The integrated source contributions from the H atoms supports the Gilli characterization scheme [14,36,37,40]. This can be explained by the fact that a classification of HBs, according to Gatti's work [37] is generally based on systems containing O-atoms.…”

Section: The Source Function In H-bonded Systemssupporting

confidence: 62%

“…Difference electron-density maps for (I) revealed the position of the H2A atom in the vicinity of atom O2, clearly indicating that the molecule exists in the monoketo-amide form and that the O1 atom of the carbonyl group is involved in an intramolecular resonanceassisted hydrogen bond [14]. The geometry of this hydrogen bond, with long O-H and short H…O distances, together with a large displacement parameter of the H atom, is typical for interactions with a broad shallow energy minimum [15].…”

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confidence: 99%

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Electronic properties of two adjacent intramolecular hydrogen bonds and their effects to the molecular charge distribution: Experimental synchrotron microcrystal and DFT computational study

2012

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The experimental crystal structure and corresponding theoretical electron density determination of 2-hydroxy-4,4-dimethyl-6-oxo-cyclohex-1-ene carboxy amide is reported with special focus on two adjacent intramolecular hydrogen bonds (O-H...O and N-H...O).The possible tautomeric forms are studied and their theoretical populations in the gas phase were determined. Additionally, theoretical models which refer to the title compound were

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Section: The Source Function In H-bonded Systemssupporting

confidence: 62%

mentioning

confidence: 99%

Electronic properties of two adjacent intramolecular hydrogen bonds and their effects to the molecular charge distribution: Experimental synchrotron microcrystal and DFT computational study

2012

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“…Moreover, it is important to bear in mind that the hydrogen bond energy as defined above cannot be taken as the real hydrogen bond strength because its values are strictly dependent on the method and the basis set adopted for calculating geometries, and the energies of the chelate and open conformations. This is clearly evident from the data of Table 3 and it is confirmed also by the rather different value (53.4 kJ mol −1 ) found by Gilli et al [26] on the grounds of his resonance assisted hydrogen bonding (RAHB) model. Therefore the best way to compare the data obtained for the title compounds is to see the variation of E HB with respect to the parent compounds I and I-H, respectively, because such difference can be associated with the strengthening of the hydrogen bridge.…”

Section: Hydrogen Bondingsupporting

confidence: 58%

Importance of steric effect on the hydrogen bond strength of malondialdehyde and acetylacetone 3‐substituted derivatives. An ab initio study

Buemi¹,

Zuccarello²

1997

Elect J Theoret Chem

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SUMMARYThe molecular geometries of various 3-substituted malondialdehyde and acetylacetone derivatives, in their chelate, open and H-centred conformations, were optimized and the hydrogen bond energies evaluated, in order to estimate the effect of 3-substitution steric hindrance on the hydrogen bond strength. Calculations were performed at the ab initio 3-21G and 6-31G** level, with and without correlation energy inclusion, using the Møller-Plesset approach (where possible) and the B3LYP functional. The frequencies of the O-H stretching mode were evaluated, too. The obtained results indicate that the Cs chelate conformations are the most stable structures. The O · · · O distances are rather longer than the values typical of the H-centred conformers, at least in gas phase. The strengthening of the hydrogen bridge, on passing from the parent to the 3-substituted derivatives, is not so relevant as expected on the ground of literature data, the maximum increase being about 21 kJ mol −1 (in 3-t-butyl-acetylacetone). An increase of the steric effect to stress the O · · · O distance caused the breaking of the hydrogen bridge instead of strengthening, so indicating that the literature X-ray geometries (in particular the O · · · O distances) are governed, at least partially, by crystalline forces.

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“…Ring A is fully aromatic both in the OEa and OOa molecules. Relatively high HOMA values for the quasirings B (0) prove that intramolecular hydrogen bonds in OEa, OOa, and EEa are of Resonance-Assisted Hydrogen Bond (RAHB) type [20][21][22][23].…”

Section: Resultsmentioning

confidence: 99%

DFT studies on tautomeric preferences of 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione in the gas phase and in solution

2010

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Density functional theory (DFT) calculations show that in vacuum such a-diketone as 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione is much less stable than its enolimine-enaminone ((1Z,3Z)-3-hydroxy-4-(pyridin-2-yl)-1-(quinolin-2(1H)-ylidene)but-3-en-2-one) and dienaminone tautomers ((1Z,3Z)-1-(pyridin-2-yl)-4-(quinolin-2-yl) buta-1,3-diene-2,3-diol). Other its tautomers (multiple basic and acidic centers in their molecules enable multiple proton transfer to take place) are even more labile. Strength of the intramolecular hydrogen bonds and aromatic character of the (quasi)rings [proved by the Harmonic Oscillator Model of Aromaticity (HOMA) index] in their molecules were found to be responsible for the observed tautomeric preferences. Polar and basic solvent disfavors and favors the enolimine and enaminone tautomers, respectively.

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Evidence for resonance-assisted hydrogen bonding from crystal-structure correlations on the enol form of the .beta.-diketone fragment

Cited by 1,100 publications

References 1 publication

Electronic properties of two adjacent intramolecular hydrogen bonds and their effects to the molecular charge distribution: Experimental synchrotron microcrystal and DFT computational study

Electronic properties of two adjacent intramolecular hydrogen bonds and their effects to the molecular charge distribution: Experimental synchrotron microcrystal and DFT computational study

Importance of steric effect on the hydrogen bond strength of malondialdehyde and acetylacetone 3‐substituted derivatives. An ab initio study

DFT studies on tautomeric preferences of 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione in the gas phase and in solution

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