Electron donating site

Low-temperature adsorption of weak CH proton-donating molecules such as CHFj, acetylene and its derivatives or HCN, enables one to chai acterize the basicity of surface electron-donating sites. 

This process of creating ATP, known as electron transport phosphorylation, then, involves two half-cell reactions, one at the electron donation site and the other where the electrons are accepted from the transport chain. Taking aerobic sulfide oxidation as an example, the donating species H2S(aq) gives up electrons, two at a time, to a series of redox complexes. With the loss of each pair of electrons, the sulfide oxidizes first to S°, then thiosulfate, sulfite, and finally sulfate. 

Systems containing olefinic moieties in addition to a cyclopropane ring pose the interesting question whether one of these functionalities is the exclusive electron donating site because of a favorable PMO energy, or whether the PMO energies are comparable. The structures of the radical cations resulting in the two cases will... 

A polyrotaxane 29 possesses two electron-donating sites (TTF and hydro-quinone moieties) as stations in the polymer backbone, hence, the incorporated cyclic acceptor 28 moves by external stimuli and possibly two translational isomers (29a and b) would exist (Scheme 10) [106, 107]. The ratio between two isomers was reported to be very solvent dependent (Table 2), with a preference however for the hydroquinone moiety. In the CV measurement, it was also observed that the cyclic acceptor 28 moved from TTF to hydroquinone moiety along the chain of 29 upon oxidation of the TTF unit. 

Saito I, Takayama M, Sugiyama H, Nakatani K, Tsuchida A, Yamamoto M. Photoinduced DNA cleavage by electron transfer— demonstration that guanine residues located 5 to guanines are the most electron donating sites. J. Am. Chem. Soc. 1995 117 6406— 6407. 

The EPR, UV-visible investigations as well as Raman scattering results provide informative clues about the formation and nature of long-lived electron-hole pairs through spontaneous biphenyl ionization upon sorption in the void space of activated ZSM-5 zeolites. The transferred electron is trapped within the framework by electron accepting site, while biphenyl radical cation captures one electron from electron donating sites of zeolite framework to restore BP ground state and causes an electron deficient hole. 

The involvement of zinc in increasing the efficiency of crosslinking is regarded to occur by some chelation of zinc with electron donating sites as ligands L such as amines, carboxylic groups of the activator, or the double bonds of the polymer chain. 

---