Mechanism for transfer of Br+ from

Figure 2. Mechanism for transfer of Br from sym(collidine) bromonium ion to...

What concerns us here are three topics addressing the fates of bromonium ions in solution and details of the mechanism for the addition reaction. In what follows, we will discuss the x-ray structure of the world s only known stable bromonium ion, that of adamantylideneadamantane, (Ad-Ad, 1) and show that it is capable of an extremely rapid degenerate transfer of Br+ in solution to an acceptor olefin. Second, we will discuss the use of secondary a-deuterium kinetic isotope effects (DKie) in mechanistic studies of the addition of Br2 to various deuterated cyclohexenes 2,2. Finally, we will explore the possibility of whether a bromonium ion, generated in solution from the solvolysis of traAU -2-bromo-l-[(trifluoromethanesulfonyl)oxy]cyclohexane 4, can be captured by Br on the Br+ of the bromonium ion, thereby generating olefin and Br2. This process would be... 

XPS measurements of passivated Fe and Ni electrodes that have been exposed to aggressive anions (Ni and Fe to F Fe to Cl , Br, and I ) but have not already formed corrosion pits support this mechanism. The quantitative evaluation of the data clearly shows a decrease of the oxide thickness with time of exposure [22,48], Not only F but also the other halides cause thinning of the passive layer (Fig. 8) [48], The catalytically enhanced transfer of cations from the oxide to the electrolyte leads to a new stationary state of the passive layer. Its smaller thickness yields an increased electrical field strength for the same potentiostatically fixed potential drop, which in turn causes faster migration of the cations through the layer to compensate for the faster passive corrosion reaction (1) at the oxide-electrolyte interface (Fig. 2a). Statistical local changes... 

Further experiments to examine the ion exchange mechanism for the acceleration in the relaxation process of the chemical oscillation were also performed. We varied the kind of hydrophilic anions (Cl , Br and I ) in the oil phase and investigated the dependence of the desorption rate of DS ions on the standard free energy of transfer of those anions. Since the ion exchange should occur at the oil/water interface, we expected that the more the standard free energy of transfer of the anions from the interface to the water phase would decrease, the more efficiently the ion exchange would occur between the hydrophilic anions and DS ions, resulting in the acceleration of the desorption... 

In physical terms, the formation of LiH in the ground state from its constituent atoms occurs by means of a transfer of an electron from the Li atom to H when the internuclear distance decreases below a critical separation R. This same concept underlies the harpoon mechanism which is used to explain the very large cross-sections for reaction which are observed for such processes as K -i- Br2 - KBr + Br. As the reactants approach, the covalent K + Br2 potential surface is intersected by an ionic K Br surface. Accordingly, an electron transfers from K to Br2. Subsequent production of KBr and Br is immediate. This model is also in accord with the observation in beam scattering experiments that the distribution of KBr product is strongly forward-peaked . 

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