Noninvertible reactions

Polarization equations are convenient when (1) the measurements are made in solutions of a particular constant composition, and (2) the equilibrium potential is established at the electrode, and the polarization curve can be measured both at high and low values of polarization. The kinetic equations are more appropriate in other cases, when the equilibrium potential is not established (e.g., for noninvertible reactions, or when the concentration of one of the components is zero), and also when the influence of component concentrations on reaction kinetics is of interest. 

Nonretaining Reactions Catalyzed by Retaining Enzymes Noninverting Reactions by Inverting Enzymes... 

Electrodes with Invertible and Noninvertible Electrode Reactions Most electrode reactions are invertible in the sense that they will occur in the opposite direction when the direction of current is inverted. Two types of reactions exist that are noninvertible in this sense. 

Reactions noninvertible on principle or, more probably, reactions for which no conditions have been found so far under which they will proceed in the opposite direction. An example of such a reaction is the cathodic reduction of hydrogen peroxide ... 

O—CH2 bond) (78, 277). More precisely, the formation of the crystalline polymer in the presence of FeCla takes place according to such a mechanism, whereas the amorphous fraction of low or zero rotatory power produced at the same time contains a sizeable number of head-to-head, tail-to-tail sequences originating from reaction at the secondary caibon [O—CH(CH3) bond] with inversion of configuration (278). From a single enantiomer, for example, (5), one obtains, by attack at the primary caibon, a noninverted unit with (5) configuration and, by attack at the secondary carbon, an inverted unit with (R) configuration (279). 

Another interesting feature related to the a nature of the cyclopropyl and vinyl radicals is their reactivity. In general, a radicals are more reactive and less selective than n radicals. Phenyl, vinyl, and cyclopropyl a radicals will abstract hydrogen atoms from saturated hydrocarbons at 77 K, conditions under which k radicals are unreactive [23]. In Ruchardt s [24] radical reactivity classification, based on the reaction of a series of o and n radicals with BrCClj and CCl, the cyclopropyl radical, an inverting a radical in an sp -hybridized orbital, closely resembled the noninverting phenyl radical. Further support for this finding... 

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