Ab Initio Study of Thiol Aqueous Phase Ionization Energies of Methyl Mercaptan and Cysteamine

Colson, Anny‐Odile; Sevilla, Michael D.

doi:10.1021/j100092a017

Cited by 10 publications

(13 citation statements)

References 9 publications

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“…(2) While the electronic affinities (EAs) and bond dissociation energies (BDEs) are very sensitive to taking into account the correlation effects, which lead in all cases to increased values, only EAs depend on the inclusion of diffuse orbitals. Nevertheless these values remain underestimated compared to the known recent experimental and theoretical data: EA = 1.77 eV for HS • and 1.34 eV for CH 3 S • in MP2/6-31+G* calculations against respectively 2.31 eV (HS • ) 32 and 1.861 eV (CH 3 S • ). ,− We have also shown the importance of the ZPE corrections (Table ), which is more evident for EA than for BDE and strongly depends on the species.…”

Section: Theoretical Sectionmentioning

confidence: 61%

“…In recent years several ab - initio calculations were performed on RSSR molecules. − Use of an extended basis set was of a prime importance to treat correctly the sulfur compounds. More recently several studies were undertaken on ions and radical sulfur derivatives with sophisticated bases, including correlation effects. ,− Ab - initio calculations have been performed, respectively, at restricted and unrestricted Hartree−Fock (RHF, UHF) levels for open and closed shell systems and at second-order Moller−Plesset (MP2) levels using two basis sets, 6-31G* and 6−31+G*. The addition of diffuse functions is generally required for proper description of anionic species .…”

Section: Theoretical Sectionmentioning

confidence: 99%

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Ab-Initio Calculations on Arginine−Disulfide Complexes Modeling the One-Electron Reduction of Lysozyme. Comparison to an Experimental Reinvestigation

et al. 1997

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The one-electron reduction of hen egg white lysozyme has been reinvestigated by γ-radiolysis using CO2 •- free radicals as reductants. We show that the reaction is specific toward one out of the four disulfide bridges, i.e. the 6−127 one. This bond is in interaction with the charged end of arginine 5. The reduction leads to thiol functions and to a lesser extent to fragmentation of the polypeptide chain, which can only come from electron migration from disulfide. To get a better insight into the mechanism induced by electron transfer to the protein, the 6−127 disulfide bridge and the charged end of arginine 5 in lysozyme were modelized by R2S2 (R = H, CH3) and C(NH2)3 +, and ab - initio calculations were performed. All separate molecular and radical entities resulting from the electron addition were optimized with two basis sets (6-31G* and 6-31+G*) and at the MP2 correlation level. The formation of complexes was studied and four zwitterionic and two neutral radical complexes involved in charge transfer reaction were characterized at the MP2 level. The influence of the environment was taken into account by using the Onsager reaction field method (SCRF) for the isolated species as well as the complexes.

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Section: Theoretical Sectionmentioning

confidence: 61%

Section: Theoretical Sectionmentioning

confidence: 99%

Ab-Initio Calculations on Arginine−Disulfide Complexes Modeling the One-Electron Reduction of Lysozyme. Comparison to an Experimental Reinvestigation

et al. 1997

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“…Since S−C bond weakening compensates for the reduced lone-pair reorganization energy on the sulfur atom (compared to oxygen), the MT barrier is not expected to be very different from methanol. This expectation is born out by the HF 6-31++G(2d,p) 480 cm -1 calculated barrier, somewhat higher than the 400 cm -1 one in methanol.…”

Section: Sulfur-containing Compoundsmentioning

confidence: 90%

Role of Lone-Pairs in Internal Rotation Barriers

1997

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An in-depth understanding of internal rotation barrier formation and energetics for dimethyl ether, protonated dimethyl ether, methanol, and their sulfur analogs is provided by dissecting the barrier into Pauli exchange steric repulsion, σ-lone-pair reorganization, and π hyperconjugation. The combined natural bond orbital, symmetry, and relaxation analysis demonstrates that oxygen σ lone-pairs play an important (sometimes dominant) role in controlling barrier heights. In dimethyl ether the increased steric contact brought about by simultaneous rotation of the methyl groups causes the COC angle to widen, in turn increasing the σ lone-pair p character, which leads to large lone-pair reorganization energy. Steric repulsion contributes to the dimethyl ether >4 kcal/mol barrier energy in only a minor way even though the steric contact can be looked at as the origin of the lone-pair increased p character. Absence of a σ lone-pair in acid media predicts a drastically lowered barrier (i.e. ∼1 kcal/mol). In methanol the increase in O atom lone-pair p character and associated lone-pair reorganization energy is strongly reduced, leading to an also greatly lowered barrier. Lone-pair σ reorganization effects are smaller in the sulfur-containing compounds, and C-S (σ) bond weakening is predicted to become the dominant barrier energy controlling term.

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“…It is 3 noteworthy that five water molecules strongly bond to the O of CH O y in aqueous solution 3 using the Monte Carlo calculation. 11 6 ᎐31G d calculation. e ( ) 11 6 ᎐31+G d calculation.…”

Section: The Enthalpy Changes ⌬ Hmentioning

confidence: 99%

“…11 6 ᎐31G d calculation. e ( ) 11 6 ᎐31+G d calculation. Full optimized structural parameters are avail-Ž .…”

Section: The Enthalpy Changes ⌬ Hmentioning

confidence: 99%

Ab initio molecular orbital study on structures and energetics of CH3O?(H2O)n and CH3S?(H2O)n in gas phase

Masamura

Ikuta

1999

J. Comput. Chem.

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The purpose of this article was to calculate the structures and energetics of CH3O−(H2O)n and CH3S−(H2O)n in the gas phase; the maximum number of water molecules that can directly interact with the O of CH3O−; and when n is larger, we asked how the CH3O− and CH3S− moiety of CH3O−(H2O)n and CH3S−(H2O)n changes and how we can reproduce experimental ΔH 0n−1, n. Using the ab initio closed‐shell self‐consistent field method with the energy gradient technique, we carried out full geometry optimizations with the MP2/aug‐cc‐pVDZ for CH3O−(H2O)n (n=0, 1, 2, 3) and the MP2/6–31+G(d,p) (for n=5, 6). The structures of CH3S−(H2O)n (n=0, 1, 2, 3) were fully optimized using MP2/6–31++G(2d,2p). It is predicted that the CH3O−(H2O)6 does not exist. We also performed vibrational analysis for all clusters [except CH3O−(H2O)6] at the optimized structures to confirm that all vibrational frequencies are real. Those clusters have all real vibrational frequencies and correspond to equilibrium structures. The results show that the above maximum number of water molecules for CH3O− is five in the gas phase. For CH3O−(H2O)n, when n becomes larger, the C—O bond length becomes longer, the C—H bond lengths become smaller, the HCO bond angles become smaller, the charge on the hydrogen of CH3 becomes more positive, and these values of CH3O−(H2O)n approach the corresponding values of CH3OH with the n increment. The C—O bond length of CH3O−(H2O)3 is longer than the C—O bond length of CH3O− in the gas phase by 0.044 Å at the MP2/aug‐cc‐pVDZ level of theory. The structure of the CH3S− moiety in CH3S−(H2O)n does not change with the n increment. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1138–1144, 1999

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Ab Initio Study of Thiol Aqueous Phase Ionization Energies of Methyl Mercaptan and Cysteamine

Cited by 10 publications

References 9 publications

Ab-Initio Calculations on Arginine−Disulfide Complexes Modeling the One-Electron Reduction of Lysozyme. Comparison to an Experimental Reinvestigation

Ab-Initio Calculations on Arginine−Disulfide Complexes Modeling the One-Electron Reduction of Lysozyme. Comparison to an Experimental Reinvestigation

Role of Lone-Pairs in Internal Rotation Barriers

Ab initio molecular orbital study on structures and energetics of CH3O?(H2O)n and CH3S?(H2O)n in gas phase

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