Electron transfer and bond breaking

The reduction of arylalkyl halides of the triphenylmethyl type by electro-chemically generated outer sphere single electron donors offers an example of a sequencing of the bond-breaking and electron-transfer steps different from what has been described before. The cleavage of the halide ion then precedes electron transfer which thus involves the carbocation, a mechanism reminiscent of 8, 1 reactions (Andrieux et ai, 1984b) as shown in (102). The... 

Anderson. D.l. Composition of the Furth." Scienie, 367 [January 20. 1OS-1 Arnett. E.M.. et al. Chemical Bond-Making, Bond-Breaking, and Electron Transfer in Solution. Sconce. 423 (January 26. 1990),... 

The +C(SH)3 cation and the radical dication derived from it have been the subject of high-level calculations.67 The ability of two adjacent sulfur atoms to stabilize cations, anions, and radicals makes these species usefiil for relating bond-breaking and electron-transfer energies.68,69 Electrophilicity parameters for the dithiocarbenium ions (27) have been worked out,70 and the stabilities of the cations (28), (29) and (30) have been estimated using PM3 calculations.71 Cation (31) can be captured by solvent or azide ion, or it may ring close to (32), which subsequently alkylates another (31) cation as shown.72... 

Proton transfer from the hydrogen peroxide molecule to His 74 is accompanied by O—H bond break and electron transfer to the oxygen atom. Then owing to the following O—H bond break and 0=0 bond formation this electron is transferred to the hydrogen atom with simultaneous hydride-ion transfer. The whole sequence of electron transfer in BRC is implemented without high-energy consumption. 

Ultrafast TRIR. The most fundamental processes of bond making, bond breaking and electron transfer have ultrafast dynamics. Access to these ultrafast time scales by TRIR requires a different approach from real-time measurements. Instead, pulsed-laser techniques based upon optical delay for measurement of time must be used. There are several approaches to measuring TRIR on the 10 — 10 s... 

In the case of simnltaneons bond breaking and electron transfer, the contribntion of the eleetronic interaction to the expectation valne of the total energy ean be also obtained from an equation similar to Eq. (30) bnt now involving the density of states of the molecular orbitals p i. Now we have to consider an additional coordinate, namely the separation between the atoms of the molecule which changes during the reaction. An analytical expression... 

Chapter 10 (Section 10.4.5) discussed the fact that enols such as 53 are inherently unstable. In other words, a simple enol such as 53 cannot be isolated. Enols undergo an internal acid-base reaction in which the OH proton is transferred to the C=C unit and the 71-bond breaks with electron transfer toward oxygen to form... 

As other examples one may quote the symmetry-breaking of the CASSCF (4e in 4MO) calculation of the inn twisted excited state of ethylene (G. Trinquier and Malrieu, in "The structirre of Double Bond". Patai ed., John Wiley (1990) p 1, or the symmetry-breaking in electron transfer problems (A. Faradzed, M. Dupuis, E. dementi and A. Aviram, J. Amer. Chem. Soc. 112, 4206 (1992). 

The reduced sites donate electrons to the reactant oxygen molecule and to intermediates formed, this electron transfer being coupled with bond breaking and making involved in the ORR process. 

Saveant JM. 1993. Electron transfer, bond breaking, and bond formation. Acc Chem Res 26 455 461. 

Electron Transfer, Bond Breaking and Bond Formation... 

ELECTRON TRANSFER. BOND BREAKING AND BOND FORMATION... 

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