Cage collapse

The observation (Porter ef a ., 1972) that added BrCCla almost completely suppresses the polarization of the olefin, while leaving the polarization of trans-4 unalfected, points to the secondary radical pair as the principal immediate precursor of a-methylstyrene. A rate constant for the decomposition of thediazenyl radical of 10 -10 sec has been estimated. Cage collapse and free-radical formation are also thought to occur and appropriately polarized products have been identified (see above). 

If you wish. As you know. Brother, the pain is so terrible that a man who does not confess on the cord cannot be hanged. Zorzi did not confess. He died. Possibly his heart stopped, or his rib cage collapsed. 

When aryl halides were applied in catalytic coupling reactions, the mechanistic evidence points to initial SET reduction by low-valent nickel phosphine species (selected investigations in [23, 24]). The competition of cage collapse to ArNi(PR3)2X vs. dissociation of the aryl halide radical anion to a free radical and Ni(I) complexes determines the cross-coupling manifolds. Thus, Ni(0)-Ni(II) and Ni(I)-Ni(III) catalytic cycles can occur interwoven with each other and a distinction may be difficult. Common to both is that the coupling process with aryl halides is likely to occur by a two-electron oxidative addition/reductive elimination pathway. 

ET from a nucleophile to an alkyl halide followed by coupling of the radicals through a cage collapse mechanism has been proposed by Lund24, Bordwell25, Ashby26 and coworkers and by others27. 

Whereas m-nitrobenzyl chloride reacts with nucleophiles by an SN1 mechanism5, m-nitrocumyl chloride5 has been reported to react with nucleophiles by a mechanism involving radical anions, free radicals and cage collapse of radical pairs rather than by an S l process. 

The formation of 119 is due to the attack of phenyl radical at thep-position of the carban-ion. The 119 118 ratio (1.7 3.7) depends on the concentration of both reactants. Competition between S l and the cage collapse mechanism has been proposed for this system. 

This reaction was suggested to occur by an S l and a cage collapse process181. On the other hand, other halonitrobenzenes, such as m- and /7-iodonitrobenzenes and o-chloro or 6>-bromo nitrobenzenes, did not react under the same conditions. 

Both, the fragmentation of R4Sn+ (Eq. 93) and the in-cage collapse of the triad (Eq. 94) are fast processes which allows the back electron transfer within the ion-radical pair to be omitted in Eq. 93 and the electron transfer (A et (Eq. 93)) to be considered as the rate-determining step [33]. As a result, the rate constants for TCNE insertion can be directly compared with rate constants of other electron-... 

The SET intermediate I could either directly form a 1,2-addition reaction product (see Scheme 13 path a no isomerization) or it could dissociate to form a radical anion and a free radical within the solvent cage. Collapse of the two radicals leads to the formation of the 1,6-addition reaction products, whereas escape from the solvent cage would lead to radical reaction products, such as benzopinacol and R- H, the result of solvent attack (Scheme 13) ... 

Acetyl peroxide, methyl acetate, dimethyl peroxide and ethane are not produced in these reactions indicating that there is no cage collapse of the radicals. Instead the methyl radicals diffuse out of the cage and react with oxygen to give methylperoxy. This means that autoxidation of acetaldehyde is terminated either by reaction of methylperoxy with acetylperoxy or by self-reaction of methylperoxy (23) and (2i+). 

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