Very strong hydrogen bonding

Emsley, John

doi:10.1039/cs9800900091

Cited by 1,102 publications

(613 citation statements)

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“…2.4 Å expected on the basis of other O-O hydrogen bonding distances involving short strong, symmetric hydrogen bonds. [35][36][37][38][39] This extrapolation may well be non-linear, however, so the intercept is at a longer O-O distance. In any case the trend of the effect of increasing the length of the hydrogen bonded chain on the internal structure of the CHD unit appears to agree qualitatively with expectations based on short-strong symmetric hydrogen-bonded systems.…”

Section: Discussionmentioning

confidence: 99%

The Crystalline Enol of 1,3-Cyclohexanedione and Its Complex with Benzene: Vibrational Spectra, Simulation of Structure and Dynamics and Evidence for Cooperative Hydrogen Bonding

et al. 2004

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The inelastic incoherent neutron scattering spectra of 1,3-cyclohexanedione (CHD) in its crystalline enol form and its cyclamer complexes with benzene and benzene-d 6 are compared with each other, with IR and Raman spectra and with the results of calculations using density functional theory (DFT). The crystal packing of the CHD enol is a linear hydrogen-bonded chain with conjugated donor and acceptor groups analogous to that found in peptide hydrogen bonding. The benzene complex is a closed hexameric hydrogen-bonded cycle. A DFT treatment is applied to the full hexamer of the benzene complex. The CHD chain is treated as a series of finite linear clusters by DFT, while the infinite one-dimensional chain and the three-dimensional crystal are treated by periodic DFT. Comparison is made with both the observed crystal structures and the vibrational spectra. The very good to excellent agreement of the computed vibrational spectra with experiment demonstrates that the models and computational treatments used are reliable. The theoretical treatment of the linear chain clusters exhibits a continuous change in structure with increasing chain length, converging to values near the observed structure. Emphasis is placed on the cooperative nature of hydrogen bonding in CHD as revealed by these systematic trends. The ability of DFT methods to treat hydrogen bonding in solids appears to be roughly as accurate as the crystal structure determinations.1,3-Cyclohexanedione (CHD) exists in its enol form in the solid state where it forms hydrogen-bonded chains with an antianti configuration having short (2.56 Å) O-O hydrogen bonding distances. 1 This structure is of interest for several reasons including the ordered hydrogen bonding arrangement, an orderdisorderphasetransitionthatinvolveshydrogenbondinterchange, 2-6 and indications derived from examination of crystal structures that CHD is an example of a resonance-assisted, cooperative hydrogen bonding network. [7][8][9][10][11][12][13] This cooperativity arises from the fact that when the enol of CHD forms a hydrogen bond, this polarizes the molecule such that the formation of an additional hydrogen bond with another CHD is more favorable. This may be thought of as due to an enhanced contribution of the ionic resonance form. When crystallized from benzene, this material forms a unique cyclamer structure (CHD 6 Bz) in which six CHD molecules form a syn-anti hydrogen bonded ring surrounding a central benzene molecule. 14 The related 1,3-cyclopentanedione (CPD) 15 forms an antianti linear chain structure very much like that of CHD. Methyl substitution of CPD or CHD can result in changes to the hydrogen-bonding pattern. 2-Methyl-CPD forms a linear chain with an anti-syn arrangement. 16 In this case the methyl-CHD molecules in a given linear chain all point in the same direction. This is in contrast to the anti-anti chain of CPD and CHD (Figure 1) where alternate molecules are oriented in opposite directions. The 2-methyl derivative of CHD has a structure similar to that of CHD 17 but t...

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Section: Discussionmentioning

confidence: 99%

The Crystalline Enol of 1,3-Cyclohexanedione and Its Complex with Benzene: Vibrational Spectra, Simulation of Structure and Dynamics and Evidence for Cooperative Hydrogen Bonding

et al. 2004

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“…[17][18][19][20] In additional experiments with TBAF trihydrate a t 77 "C (2 torr) we noted not only mass loss as a function of time but also changes in physical appearance as well. For example, when placed at 77 OC, the crystalline trihydrate immediately melted to a colorless liquid from which bubbles evolved.…”

Section: Results a N D Discussionmentioning

confidence: 94%

Direct preparation of bromoacetaldehyde

Kraus¹,

Gottschalk²

1983

J. Org. Chem.

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Halo aldehydes or their equivalents have been widely employed in heterocyclic synthesis. Such aldehydes are useful for ring-forming reactions in that they represent units with two adjacent electrophilic sites. However, the simplest representatives, bromo-or chloroacetaldehyde, have been little used because the anhydrous aldehyde is difficult to prepare. J. Org. Chem. 1983,48, 2111-2112 2111 the solid residue, dissolved in MeOH, was filtered and dried in vacuo, followed by HPLC separation (Altex columns with MeOH/H20 (91) as mobile phase), to yield 1.5 mg of 2b and 32 mg of starting compound lb. The high-resolution mass and 'H NMR spectra of 2b were identical in all respects with those of natural 2b. Disciplines3@,11-Dihydroxy-9,11-secogorgost-5-en-9-one (la):' absorption spectrum tm 51; CD -3350, -4800.Isomerization of 3/3,1l-Dihydroxy-9,ll-secogorgost-5-en-9-one (la) to 8a-H Isomer 2 a A 50-mg eample of la was treated in the same way as described above for lb. The final HPlC separation yielded 2 mg of 2a (HPLC rrt 0.14 with cholesterol = 1) and 35 mg of la. Absorption spectrum of 2a: c2a 147; CD Acetylation of l b and 3b to 3@,11-Diacetoxy-24-methylene-9,ll-secocholest-5-en-9-one (4b). Both lb and 3b were acetylated under standard conditions (AczO/py, room temperature, 2 h) to yield the same diacetate 4b, which was purified by HPLC on Altex columns with MeOH/H20 (

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“…To compensate the loss of entropy, a large gain in enthalpy of association (920 kcal mol -1 ) is needed, which in this case can only be achieved via multiple van der Waals contacts between the bulky adamantyl moiety and the inner cavity of CD. Since the enthalpy of -OH … O = and -NH … O-hydrogen bonds typically amounts to less than 5 kcal mol -1 [49], at least 4 hydrogen bonds are required to compensate the loss of entropy found for the model assemblies. However, AdNAc and CD do not allow for the formation of 4 hydrogen bonds.…”

Section: Stability Of the Complexes In Solution And In The Gas Phasementioning

confidence: 99%

What Happens to Hydrophobic Interactions during Transfer from the Solution to the Gas Phase? The Case of Electrospray-Based Soft Ionization Methods

Barylyuk

Balabin

Grünstein

et al. 2011

J. Am. Soc. Mass Spectrom.

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The disappearance of the hydrophobic effect in the gas phase due to the absence of an aqueous surrounding raises a long-standing question: can noncovalent complexes that are exclusively bound by hydrophobic interactions in solution be preserved in the gas phase? Some reports of successful detection by mass spectrometry of complexes largely stabilized by hydrophobic effect are questionable by the presence of electrostatic forces that hold them together in the gas phase. Here, we report on the MS-based analysis of model supramolecular complexes with a purely hydrophobic association in solution, β-cyclodextrin, and synthetic adamantyl-containing ligands with several binding sites. The stability of these complexes in the gas phase is investigated by quantum chemical methods . Compared with the free interaction partners, the inclusion complex between β-cyclodextrin and adamantyl-containing ligand is shown to be stabilized in the gas phase by ΔG = 9.6 kcal mol -1 . The host-guest association is mainly enthalpy-driven due to strong dispersion interactions caused by a large nonpolar interface and a high steric complementarity of the binding partners. Interference from other types of noncovalent binding forces is virtually absent. The complexes are successfully detected via electrospray ionization mass spectrometry, although a high dissociation yield is also observed. We attribute this pronounced dissociation of the complexes to the collisional activation of ions in the atmospheric interface of mass spectrometer. The comparison of several electrospray-based ionization methods reveals that cold spray ionization provides the softest ion generation conditions for these complexes.

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Very strong hydrogen bonding

Abstract: These bands are caused by Fermi resonance of VAH with the in-plane, I AH, and out-of-plane, YAH, bending modes, i.e. 2 8 ~~ and 2YAH. Moreover it has been shown that the minima in the ABC band represent the overtone frequencies. CJ M. F. Claydon and N. Sheppard,

Cited by 1,102 publications

References 3 publications

The Crystalline Enol of 1,3-Cyclohexanedione and Its Complex with Benzene: Vibrational Spectra, Simulation of Structure and Dynamics and Evidence for Cooperative Hydrogen Bonding

The Crystalline Enol of 1,3-Cyclohexanedione and Its Complex with Benzene: Vibrational Spectra, Simulation of Structure and Dynamics and Evidence for Cooperative Hydrogen Bonding

Direct preparation of bromoacetaldehyde

What Happens to Hydrophobic Interactions during Transfer from the Solution to the Gas Phase? The Case of Electrospray-Based Soft Ionization Methods

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