Solvated electron free energy

The gas-phase lifetime of N20- is 10-3 s in alkaline solutions, it is still >10-8 s. Under suitable conditions, N20- may react with solutes, including N20. The hydrated electron reacts very quickly with NO (see Table 6.6). The rate is about three times that of diffusion control, suggesting some faster process such as tunneling. NO has an electron affinity in the gas phase enhanced upon solvation. The free energy change of the reaction NO + eh (NO-)aq is estimated to be --50 Kcal/mole. Both N02- and N03- react with eh at a nearly diffusion-controlled rate. The intermediate product in the first reaction, N02-, generates NO and... 

Within this framework, by considering the physical situation of the electrode double layer, the free energy of activation of an electron transfer reaction can be identified with the reorganization energy of the solvation sheath around the ion. This idea will be carried through in detail for the simple case of the strongly solvated... 

Similarly, changes must take place in the outer solvation shell diirmg electron transfer, all of which implies that the solvation shells themselves inliibit electron transfer. This inliibition by the surrounding solvent molecules in the iimer and outer solvation shells can be characterized by an activation free energy AG. ... 

As with SCRF-PCM only macroscopic electrostatic contribntions to the Gibbs free energy of solvation are taken into account, short-range effects which are limited predominantly to the first solvation shell have to be considered by adding additional tenns. These correct for the neglect of effects caused by solnte-solvent electron correlation inclnding dispersion forces, hydrophobic interactions, dielectric saturation in the case of... 

RB Yelle, T Ichiye. Solvation free energy reaction curves for electron transfer Theory and simulation. J Phys Chem B 101 4127-4135, 1997. 

The free energy of activation at the QCISD(T)/6-31 H-- -G(d,p) level amounts to 21.1 kcal/mol. According to the authors, the large electron density redistribution arising upon cyclization makes it necessary to use extended basis sets and high-order electron correlation methods to describe the gas-phase thermodynamics, which indicates clearly the gas-phase preference of the azido species. However, the equilibrium is shifted toward the tetrazole as the polarity of a solvent is increased. For instance, SCRF calculations (e = 78.4) yield a relative free energy of solvation with respect to the cw-azido isomer of —2.4 kcal/mol for the tmns-zziAo compound and of —6.8 kcal/mol for the tetrazole isomer. At a much lower level, the... 

At electrode potentials more negative than approximately - 2.8 V (SHE), free solvated electrons appear in the solution as a result of (dark) emission from the metal. At this potential the electrochemical potential of the electrons according to Eq. (29.6) is about —1.6 eV, which is at once the energy of electron hydration in electron transfer from vacuum into an aqueous phase. 

Equation (34.10) describes the dependence of the activation free energy on the free energy of transition AF for electron transfer between two discrete energy levels (one in the donor, Eq, and one in the acceptor, e ). The quantity AF involves the difference of these electron energies, the solvation free energies of the reaction products, wfi and the initial reactants, wf and the works required to bring the reaction products, w, and the reactants, w,., from infinity to a given interreactant distance 34. 

The configurational model was used for the calculation of the elementary act in the reactions of solvated electrons21 and in the electrochemical generation of solvated electrons.22 The results for the activation free energy of the process of electrochemical generation of solvated electrons as a function of the reaction free energy... 

Dependence of the Kinetic Parameters for the Reaction of Electrochemical Generation of Solvated Electrons on the Free Energy of the Transition... 

Marchi, M. Sprik, M. Klein, M. L., Calculation of the free energy of electron solvation in liquid ammonia using a path integral quantum Monte Carlo simulation, J. Phys. Chem. 1988, 92, 3625-3629... 

The dielectric response of a solvated protein to a perturbing charge, such as a redox electron or a titrating proton, is related to the equilibrium fluctuations of the unperturbed system through linear response theory [49, 50]. In the spirit of free energy... 

Fig. 12.2. Free energy data for electron transfer between the protein cytochrome c and the small acceptor microperoxidase-8 (MP8), from recent simulations [47]. Top Gibbs free energy derivative versus the coupling parameter A. The data correspond to solvated cytochrome c the MP8 contribution is not shown (adapted from [47]) Bottom the Marcus diabatic free energy curves. The simulation data correspond to cyt c and MP8, infinitely separated in aqueous solution. The curves intersect at 77 = 0, as they should. The reaction free energy is decomposed into a static and relaxation component, using the two steps shown by arrows a static, vertical step, then relaxation into the product state. All free energies in kcalmol-1. Adapted with permission from reference [88]...

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