Carbonium ion migration

However, these reactions do not agree with the ESR spectra observed by Ohnishi et al. (32). Another possibility involving carbonium ion migration is ... 

The acid catalyzed rearrangements of peroxides, in which the migrating groups show the same migration aptitudes as in carbonium ion rearrangements, may be represented as rearrangements of oxygen cations.89-91... 

In the presence of ferrous salts the hydroperoxide decomposition goes by way of an oxygen monoradical intermediate, with different migration aptitudes. Para nitrophenyl rather than phenyl migrates under the radical conditions. Although the oxygen cation resembles the carbonium ion both chemically and in charge type, it may also be a diradical ... 

Since it is not always known to what extent the departing group is still present at the rearrangement stage of the reaction, a detailed interpretation of migration aptitudes is difficult. The examples just discussed, however, should certainly not be compared with migration aptitudes within a fully formed carbonium ion. 

The abnormal ozonolysis is chiefly observed when the group R is one that shows a high migration aptitude in carbonium ion rearrangements. 

Just as in its carbonium ion twin, the carbanion rearrangement takes place with retention of configuration of the migrating group. This proves at once that the reaction is intramolecular and that the displacement takes place at the front side.428... 

The anion presumably plays only a minor role, if any, especially in aqueous systems. Now the formation of 3-hexene may be explained in either of two ways. The intermediate carbonium ion, written in brackets, can undergo hydride migration to form a new carbonium ion, which can then collapse by proton loss to form the 3-hexene. Such a process does not require the intermediate formation of 2-hexene. The alternate explanation involves the discrete formation of 2-hexene followed by addition and elimination of a proton to give the desired 3-hexene. There is no question but that the hydride migration occurs, and with great... 

Stern showed rather conclusively that the palladium does not depart to leave a carbonium ion but that both hydride migration and collapse to an aldehyde proceed simultaneously. The removal of the /3 hydrogen in a complexes by the heavier Group VIII metals has been documented. Thus Chatt and Shaw (63) showed that a platinum hydride complex could undergo the reversible addition of ethylene ... 

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