Ethanes homolytic cleavage

FIGURE 11.3 Two possible bond breakings in ethane. Homolytic cleavage requires less energy because no charges are generated. 

Problem 3.3 Write formulas for the speeies resulting from the ( ) homolytic cleavage, (b) heterolytic cleavage of the C—C bond in ethane. C,H . and classify these species. ... 

The addition of radical scavengers, such as TEMPO, suppressed the formation of ethane, methane, and methyl chloride, instead leading rally to the observation of TEMPO-Me (35) and Pd(II) complex 34 (Fig. 19). The observed reaction with radical scavengers is consistent with photo-induced homolytic Pd-C bond cleavage... 

The quantitative ESR measurements reported later by Bon et al. [135] proved to be a rather straightforward and accurate means to determine the rate coefficients for the homolytic alkoxyamine C-O bond cleavage over a range of temperatures for 2-tert-butoxy-l-phenyl-l-(l-oxy-2,2,6,6-tetramethylpiperidinyl)ethane and a polystyrene-TEMPO. The acquired kinetic data for alkoxyamines were compared by the authors with data obtained via nitroxide-exchange experiments using HPLC and with literature data [137]. 

Mansuy et al. employed alkyl peroxides and iodosylbenzene as oxygen donors and examined the oxidation products of cyclohexane in the presence of a series of M(TPP) complexes (M=Fe, Mn, Co, Rh, and Cr) [284]. As listed in Table 10, cyclohexanol and cyclohexanone are the major products however, the ratio of the alcohol and ketone was dependent on the oxidant employed. For the oxidation by peroxides, involvement of alkoxy radical (RO ) due to the homolytic 0-0 bond cleavage of R-OO-M was proposed. In order to trap possibly formed radical intermediates. He and Bruice examined the oxidation of cw-stilbene and (Z)-l,2-bis(fran5-2,tran5-3-diphenylcyclopropyl)ethane by iron porphyrin/f-BuOOH system [285]. In separate experiments, AIBN was used as a radical chain initiator for the oxidation of the alkenes by t-BuOOH. According to the product distribution, they concluded the products to be derived from initial combination of t-BuOO, rather than 0=Fe (por)", with olefin. 

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