Atoms reduction

N-Linked substituents O-Linked substituents S-Linked substituents C-Linked substituents Reactivity at the Ring Nitrogen Atoms Reduction Oxidation... 

KC8 also affords a borate salt, but in this case it is uniquely dimerized with a relatively long (1.83(2) A) B-B bond, which is caused, no doubt, by the presence of adjacent negative charges and the four-coordination of the boron atoms. Reduction of 2,6-Trip2H3C6BBr2 with sodium gave the 9-borafluorenyl radical anion salt, which was characterized by EPR and elemental analysis.67... 

Fig. S-S8. Electron levels of dehydrated redox particles, H ld + bh /h = H,d, adsorbed on an interface of metal electrodes D = state density (electron level density) 6 = adsorption coverage shVi - most probable vacant electron level of adsorbed protons (oxidants) eH(d = most probable occupied electron level of adsorbed hydrogen atoms (reductants) RO.d = adsorbed redox particles.

The isolated silver atom formed in this reaction could take part in latent image formation either by diffusion to a latent sub-center or by thermal dissociation with the transfer of an electron to the conduction band. Hence, it is theoretically possible that the absorption of one photon by the silver halide results in two latent image silver atoms. Reduction centers larger than Ag2 could not contribute additional silver to the latent image in this way until their size had been decreased to two atoms by reaction with holes. 

Schuchmann H-P, von Sonntag C (1988) The oxidation of methanol and 2-propanol by potassium peroxodisulphate in aqueous solution free-radical chain mechanisms elucidated by radiation-chemical techniques. Radiat Phys Chem 32 149-156 Schwarz HA, Bielski BHJ (1986) Reactions of H02 and 02 with iodine and bromine and l2 and I atom reduction potentials. J Phys Chem 90 1445-1448... 

Alkyl halides other than aryl and vinyl halides do not readily undergo oxidative addition with Pd and must, in general, first be converted to alkylmetals. In this connection, however, a recent report on the Ni catalysed selective alkyl-alkyl cross-coupling with Ni(acac)2 and Lil in THF represents a significant breakthrough.34 In cases where the alkyl group contains a p-H atom, reduction of the organic halide via p-dehydropalladation reductive elimination can be a serious side-reaction (Scheme 11.6). 

The CT inner-sphere, photoinduced redox reaction results in oxidation (or reduction) of the central atom at the expense of the respective reduction (or oxidation) of ligand. The direction of the redox process depends on the CT state character (see Figure 3.1 and section 3.2 in Chapter 3) the central atom reduction is a consequence of the LMCT transition, whereas central atom oxidation is a result of the MLCT transition (Figure 6.7). The photochemical oxidation of one ligand at the expense of another (LLCT) can also be rated among the inner-sphere redox processes (see above). 

Enamines have so far been shown to undergo two types of radical reactions as shown by equations 1 and 2. The addition of a carbon-centered radical to the C=C bond of enamines (equation 1) leads to a nitrogen substituted radical which then either transfers an electron to a suitable electron acceptor to form an iminium ion or abstracts a hydrogen atom (reductive homolytic alkylation). 

Acetoxymercuriation of cyclopropanes. keaction of Hg(OAc), with cyclopropanes results in attack at the least substituted carbon atom. Reduction of the product in the presence of an electron-deficient alkene results in coupling of the intermediate radical to the least substituted carbon atom of the alkene. 

A much more frequently used reaction is the cleavage of unsaturated compounds to aldehydes (equations 98 and 99). Alkenes and cycloalkenes that possess one or two hydrogens at the double bonds are oxidized by ozone to ozonides, which have to be reduced to prevent a subsequent oxidation to acids by the excess oxygen atom. Reductions are carried out, usually without isolation of the ozonides, by catalytic hydrogenation over palladium catalyst [80, 81,1106] or Raney nickel [55] or by treatment with... 

In contrast to oxidation of the sulfur atom, reduction of sulfur (also called extrusion or elimination) from thiiranes and thiirenes is a relatively facile process. Virtually all thiiranes and thiirenes, as well as their oxides and dioxides, undergo thermal extrusion of the sulfur moiety with increasing facility according to the trend S SO < S02. 

The authors of Ref.[142] believe the whole process to take place around the coordination sphere of the transition-metal catalyst. Most experimental facts related to olefin hydro-silylation (predominance of the terminal adduct, olefin isomerization, stereochemistry ot the silicon atom, reductive catalyst deactivation) have been explained in terms of the proposed mechanism. 

Oxidation occurs when hydrogen atoms are removed from a carbon atom or when an oxygen atom is added to a carbon atom. Reduction occurs when hydrogen... 

Several studies in recent years have focussed on the preparation and characterization of metal particles in zeolites (1). Various ways have been developed to introduce metals and metal precursors including sublimation (2), adsorption (3), and ion-exchange (4). If it is desirable to remove the ligands from the precursor metal complexes many approaches can be used including high temperature reduction in hydrogen (5), photochemical degradation (6), sodium (7) or cadmium (8) reduction, H atom reduction (9), low temperature vacuum treatments (10) and plasma methods (11). 

Oxidation is defined as a loss of electrons, loss of hydrogen atoms, or gain of oxygen atoms. Reduction is defined as a gain of electrons, gain of hydrogen atoms, or loss of oxygen atoms. 

Even this is not all. A fourth molecule of formaldehyde reacts with hydroxide ion and then reduces the third aldoL This reduction is known as the Cannizzaro reaction, and is described in the box. The final product is the highly symmetrical pentaerythritoT, C(CH20H)4, with four CH2OH groups joined in a tetrahedral array about the same carbon atom, reduction by the Cannizzaro reaction... 

A detailed model is provided and justified that represents the ATRP equilibrium constant as a combination of contributing equilibria C-X bond homolysis, electron affinity of the halogen atom, reduction of Cu, and the... 

Nickel(0)-catalyzed [2 + 2 + 2] cocyclization of the precursor (177) in the presence of several chiral ligands afforded the chiral tetrahydroisoquinoline (178) in a novel asymmetric cycloaddition. Compound (178) could be transformed into the benzo[a]quinolizidine (180), albeit in modest enantiomeric excess, through a multistep route involving extension of the alkynic side chain at C-1 to yield (179), introduction of a cu halogen atom, reduction of the triple bond, A(-deprotection and final eyelization (Scheme 29) <94J0C6133>. 

---