Hydrophobic solvation, quantum nature, and diffusion of atomic hydrogen in liquid water

Roduner, Emil

doi:10.1016/j.radphyschem.2004.09.014

Cited by 31 publications

(32 citation statements)

References 14 publications

(19 reference statements)

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“…In Parker’s early analysis,48 Δ G solv °(H • ) was approximated using solvation energies of the noble gases. Roduner has now shown that the solvation of H • is better approximated as that of H 2 50. On that basis, we have calculated revised values for C G in several different solvents (Table 1),39,51 using known values of Δ G solv °(H 2 ) 52–5354.…”

Section: Thermochemical Backgroundmentioning

confidence: 99%

“…These gas phase values are within 1 kcal mol −1 of methane. These BDEs and BDFEs, along with the known enthalpies and entropies of solution, are used to calculate BDEs and BDFEs in various solvents, using Roduner’s 2005 demonstration that the solvation of H • is energetically roughly equal to that of H 2 50. As described in Section 3.1 above, use of this approximation has led to revision of the H + /H • reduction potentials in different solvents.…”

Section: Thermochemistry Of Pcet Reagentsmentioning

confidence: 99%

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Thermochemistry of Proton-Coupled Electron Transfer Reagents and its Implications

2010

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Section: Thermochemical Backgroundmentioning

confidence: 99%

Section: Thermochemistry Of Pcet Reagentsmentioning

confidence: 99%

Thermochemistry of Proton-Coupled Electron Transfer Reagents and its Implications

2010

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“…4) by using S ∘ ðH • Þ ¼ 27.42 cal K −1 mol −1 and the common assumption that S ∘ ðXHÞ ∼ S ∘ ðX • Þ for organic compounds (21)(22)(23). Converting these to solution BDFEs (BDFE solv ) requires ΔG ∘ solv ðH • Þ in a given solvent (24) and the difference in the free energy of solvation of XH and X • (Eq. 5).…”

Section: Resultsmentioning

confidence: 99%

Predicting organic hydrogen atom transfer rate constants using the Marcus cross relation

Warren

Mayer

2010

Proc. Natl. Acad. Sci. U.S.A.

112

137

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Chemical reactions that involve net hydrogen atom transfer (HAT) are ubiquitous in chemistry and biology, from the action of antioxidants to industrial and metalloenzyme catalysis. This report develops and validates a procedure to predict rate constants for HAT reactions of oxyl radicals (RO • ) in various media. Our procedure uses the Marcus cross relation (CR) and includes adjustments for solvent hydrogen-bonding effects on both the kinetics and thermodynamics of the reactions. Kinetic solvent effects (KSEs) are included by using Ingold's model, and thermodynamic solvent effects are accounted for by using an empirical model developed by Abraham. These adjustments are shown to be critical to the success of our combined model, referred to as the CR/KSE model. As an initial test of the CR/KSE model we measured self-exchange and cross rate constants in different solvents for reactions of the 2,4,6-tri-tert-butylphenoxyl radical and the hydroxylamine 2,2′-6,6′-tetramethylpiperidin-1-ol. Excellent agreement is observed between the calculated and directly determined cross rate constants. We then extend the model to over 30 known HAT reactions of oxyl radicals with OH or CH bonds, including biologically relevant reactions of ascorbate, peroxyl radicals, and α-tocopherol. The CR/KSE model shows remarkable predictive power, predicting rate constants to within a factor of 5 for almost all of the surveyed HAT reactions.free radicals | Marcus theory | proton-coupled electron transfer | reactive oxygen species | oxyl radicals H ydrogen atom transfer (HAT) reactions (Eq. 1) have been a cornerstone of organic and biological chemistry for over a century (1, 2). These reactions are key steps in many important processes, from energy conversion to the chemistry of reactive oxygen species and antioxidants (3). Thus, developing a detailed understanding of the factors that dictate HAT reactivity has long been a goal.A large number of HAT rate constants have been measured in many laboratories with various techniques (4, 5). Rates of HAT reactions have traditionally been understood by using the BellEvans-Polanyi (BEP) relation, which relates the activation energy to the enthalpic driving force (6). Whereas the BEP relation holds well within sets of similar reactions, a comprehensive theoretical understanding of HAT is still emerging (3).Our group has been exploring the use of the Marcus cross relation (CR) Eq. 2 (7), a corollary of the Marcus theory of electron transfer, as the basis for a general model for HAT rates (8)(9)(10)(11)(12). This use of the CR grew out of recognizing HAT as one class of a larger set of reactions in which one electron and one proton are transferred (, termed proton-coupled electron transfer. In this paper, we use "HAT" to refer to any reaction in which H • is transferred from a donor to an acceptor in a single kinetic step (Eq. 1), although other definitions have been used (13).The CR, with respect to HAT reactions, relates the cross rate constant (k XH∕Y• , Eq. 1) to the two degenerate self-exchange rate c...

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“…Bartels (2009) assumed that the temperature dependence of D hydr G OH (m) is the same as that of D hydr G H 2 OðmÞ , increasing from À17.9 to À10.2 kJ mol À1 from 298 to 573 K with reference to equal density standard states, whereas Marin et al (2003) suggested that D hydr G OH(m) changes by less than 10% between 25 and 350 1C. On the other hand, it is known from computer simulations that up to the subcritical region OH occupies a cage in the H-bonded network of water (Svishchev and Plugatyr, 2005) like H and H 2 (Roduner, 2005). Thus one might expect D hydr G OH(m) to show an increase similar to that of D hydr G H 2 ðmÞ , i.e.…”

Section: High Temperature (T ¼ 57315 K)mentioning

confidence: 99%

Reply to comment on the possible role of the reaction H+H2O→H2+OH in the radiolysis of water at high temperatures

Swiatla-Wojcik

Buxton²

2010

Radiation Physics and Chemistry

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Hydrophobic solvation, quantum nature, and diffusion of atomic hydrogen in liquid water

Cited by 31 publications

References 14 publications

Thermochemistry of Proton-Coupled Electron Transfer Reagents and its Implications

Thermochemistry of Proton-Coupled Electron Transfer Reagents and its Implications

Predicting organic hydrogen atom transfer rate constants using the Marcus cross relation

Reply to comment on the possible role of the reaction H+H2O→H2+OH in the radiolysis of water at high temperatures

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