Peculiar Structure of the HOOO<sup>-</sup> Anion

Kraka, Elfi; Cremer, Dieter; Koller, J.; Plesničar, Božo

doi:10.1021/ja012553v

Cited by 37 publications

(61 citation statements)

References 64 publications

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“…The CH 3 SSOH system is very peculiar and can be regarded as an intermediate situation between CH 3 SSNH 2 and CH 3 SSF since both SÀS and SÀX bonds become activated upon electron attachment. Previous results on the HOOO anion [48] showed that the OÀOH bond is preferentially broken rather than the OÀOO one, based on the aforementioned anomeric effect. Consequently, an analogous cleavage should be expected for CH 3 SSOH.…”

Section: Resultsmentioning

confidence: 88%

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Asymmetry and Non‐Adiabaticity in Fragmentation of Disulfide Bonds upon Electron Capture

Gámez¹,

Serrano‐Andrés²,

Yáñez³

2010

ChemPhysChem

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Although it has been generally assumed that electron attachment to disulfide derivatives leads to a systematic and significant activation of the S-S bond, we show, by using [CH(3)SSX] (X = CH(3), NH(2), OH, F) derivatives as model compounds, that this is the case only when the X substituents have low electronegativity. Through the use of MP2, QCI and CASPT2 molecular orbital (MO) methods, we elucidate, for the first time, the mechanisms that lead to unimolecular fragmentation of disulfide derivatives after electron attachment. Our theoretical scrutiny indicates that these mechanisms are more intricate than assumed in previous studies. The most stable products, from a thermodynamic viewpoint, correspond to the release of neutral molecules; CH(4), NH(3), H(2)O, and HF. However, the barriers to reach these products depend strongly on the electronegativity of the X substituents. Only for very electronegative substituents, such as OH or F, the loss of H(2)O or HF is the most favorable process, and likely the only one observed. This is possible because of two concomitant factors, 1) the extra electron for [CH(3)SSX](-) (X = OH, F) occupies a sigma*(S-X) MO, which favors the cleavage of the S-X bond, and 2) the activation barriers associated with the hydrogen transfer process to produce H(2)O and HF are rather low. Only when the substituents are less electronegative (X = H, CH(3), NH(2)) the extra electron is located in a sigma*(S-S) orbital and the cleavage of the disulfide bridge becomes the most favorable process. The intimate mechanism associated with the S-S bond dissociation process also depends strongly on the nature of the substituent. For X = H or CH(3) the process is strictly adiabatic, while for X = NH(2) it proceeds through a conical intersection (CI) associated with the charge reorganization necessary to obtain, from a molecular anion with the extra electron delocalized in a sigma*(S-S) antibonding orbital, two fragments with the proper charge localization.

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Section: Resultsmentioning

confidence: 88%

“…Previous results on the HOOO anion [48] showed that the OÀOH bond is preferentially broken rather than the OÀOO one, based on the aforementioned anomeric effect. Consequently, an analogous cleavage should be expected for CH 3 SSOH.…”

Section: Wwwchemphyschemorgmentioning

confidence: 88%

Asymmetry and Non‐Adiabaticity in Fragmentation of Disulfide Bonds upon Electron Capture

Gámez¹,

Serrano‐Andrés²,

Yáñez³

2010

ChemPhysChem

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“…At the highest levels used here, the heats of formation for HO 3 H and HO 4 H are, respectively, −22.12 kcal/mol ( F//D level) and −11.48 kcal/mol ( E//D level), which are not far from recent estimations by other authors. Thus, for HO 3 H, values of −22.7 kcal/mol56, −23.0 kcal/mol57, and −21.50 kcal/mol17 have been reported. The most recent value computed for HO 4 H is −10.61 kcal/mol17.…”

Section: Resultsmentioning

confidence: 97%

Structure, stability, and dynamics of hydrogen polyoxides

Martins‐Costa

Anglada

Ruiz‐López

2010

Int J of Quantum Chemistry

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ABSTRACT:Hydrogen polyoxides H 2 O n have been theoretically studied in gas phase and in aqueous solution. Structures up to n ¼ 4 have been detected experimentally. Larger systems are speculative till now but previous calculations predicted stable structures. Minimum energy geometries and formation enthalpies for n ¼ 3-10 have been calculated in gas phase using high-level ab initio calculations that include DFT, QCISD, and CCSD(T) methods. Formation enthalpies are negative for n < 5, close to zero for n ¼ 5, and positive for n > 5. They go up by $12-16 kcal/mol per O atom although the increase is not regular; it presents an oscillatory behavior that is clearly connected with odd/even effects reported for OO bond lengths. Computations in aqueous solution focus on free energies of solvation, solute-solvent hydrogen bonds strength, and solvent effects on polyoxide structure. We use two solvent models. A dielectric continuum implicit model is used to estimate free energies of solvation at an affordable cost. An explicit model is then used combining a QM/MM description of the solution and molecular dynamics (MD) simulations for polyoxides n ¼ 3-6. The solute is described at the DFT level whereas solvent molecules are treated with an empirical force field. The analysis of the solute dynamics in solution shows that the systems are very good proton donors but poor proton acceptors. The structure with n ¼ 5 exhibits a particular behavior that seems to be related with its larger statistical probability of forming intramolecular hydrogen bonds. Most bonds are lengthened in solution, especially the polar HAO bonds and the inner OAO bonds. Remarkably, the amplitude of OAO bond length fluctuations has been shown to depend primarily on its position along the chain, that is, the distance with respect to the terminal HAO bond, and less on chain length. For n ¼ 6, the central OAO bond fluctuates between 1.2 and 1.9 Å . Chains beyond n ¼ 6 should be extremely labile since fluctuations of the central OAO bonds should be even larger. Hence, if formed, the corresponding lifetimes should be extremely short.

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“…[1][2][3][4][5][6] Increasing evidence shows that ozonation reactions with organic substrates lead to hydrotrioxides, as was already speculated for a long time. [7][8][9] Plesnicar and co-workers used 17 O-enriched ozone to verify the existence of HOOOH and ROOOH in the reaction mixture of ozone and isobutyl alcohol.…”

Section: Introductionmentioning

confidence: 92%

¹⁷O NMR Chemical Shifts of Polyoxides in Gas Phase and in Solution

Wu¹,

Cremer²,

Gauß³

2003

J. Phys. Chem. A

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The 17 O NMR chemical shift values of polyoxides HO n H, CH 3 O n H, and CH 3 O n CH 3 (n ) 2, 3, 4) were calculated using four different methods (GIAO-HF, GIAO-MP2, GIAO-CCSD(T), and IGLO-DFT) and various basis sets ranging from double to quadruple quality. The 17 O shift values depend on the number of O atoms in the polyoxide chain and on the terminal group (H or alkyl) and are spread over a large range (200-600 ppm relative to H 2 O) due to a (diamagnetic) shielding effect caused by electron attraction by the electronegative O atom and a (paramagnetic) deshielding effect caused by anomeric delocalization. Solvent shifts result from both nonspecific and specific solvation. Nonspecific solvation normally leads to a shielding of 17 O by up to 20 ppm, whereas specific solvation is strongly deshielding, causing a net effect of 20-36 ppm. An empirical scheme is suggested to predict measured values with an accuracy of better than 5 ppm using GIAO-MP2/qzp gas-phase values with GIAO-CCSD(T) estimates of higher-order correlation corrections as well as specific and nonspecific solvation corrections. Averaging of NMR chemical shifts due to the rotational flexibility of the polyoxides has little influence on the measured 17 O NMR chemical shifts.

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Peculiar Structure of the HOOO^- Anion

Cited by 37 publications

References 64 publications

Asymmetry and Non‐Adiabaticity in Fragmentation of Disulfide Bonds upon Electron Capture

Asymmetry and Non‐Adiabaticity in Fragmentation of Disulfide Bonds upon Electron Capture

Structure, stability, and dynamics of hydrogen polyoxides

¹⁷O NMR Chemical Shifts of Polyoxides in Gas Phase and in Solution

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Peculiar Structure of the HOOO- Anion

Cited by 37 publications

References 64 publications

Asymmetry and Non‐Adiabaticity in Fragmentation of Disulfide Bonds upon Electron Capture

Asymmetry and Non‐Adiabaticity in Fragmentation of Disulfide Bonds upon Electron Capture

Structure, stability, and dynamics of hydrogen polyoxides

17O NMR Chemical Shifts of Polyoxides in Gas Phase and in Solution

Contact Info

Product

Resources

About

Peculiar Structure of the HOOO^- Anion

¹⁷O NMR Chemical Shifts of Polyoxides in Gas Phase and in Solution