Cross disproportionation occurs when two different alkyl radicals disproportionate to form two new products.
Different products can be formed depending on which alkyl radical acts as a donor and which acts as an acceptor.
When the alkyl radical is fully formed in the transition state it can benefit fully from any resonance stabilization present thereby maximizing selectivity.
The nomenclature parallels that of alkyl radicals.
In the primary reaction product the intermediate alkyl radical is then captured by the diazonium counterion X which is usually a halogen or a tetrafluoroborate.
The alkyl radical will typically react rapidly with oxygen forming a peroxy radical.
One electron from the metal is transferred to the halogen to produce a metal halide and an alkyl radical.
The reaction of the alkyl radical with the ester carbonyl group is also a possibility but has an unfavorable activation energy.
Likewise, radicals next to functional groups such as carbonyl, nitrile, and ether are more stable than tertiary alkyl radicals.
It has been postulated that after electron transfer, immediate recombination of the fluorine radical with the alkyl radical takes place.