The following observations support the concerted pericyclic mechanism, and refute the stepwise diradical or the stepwise polar pathway.
12.
Therefore, bound OCCO is formally a diradical, with an electronic structure motif similar to the oxygen molecule.
13.
Oxygen is unique among most oxidisers in that it is a diradical, usually found in triplet oxygen state.
14.
Many radiomimetic compounds are enediynes, which undergo the Bergman cyclization reaction to produce the para-benzyne diradical.
15.
The p-benzyne diradical is highly reactive, and will abstract hydrogens from any possible hydrogen-donor.
16.
This does not make sense to me-triplet oxygen cannot have a double bond and concurrently be a diradical.
17.
The SiH 2 Na 2 dissolves in the mercury to generate the diradical SiH 2, which then forms the final products.
18.
The HDDA [ 4 + 2 ] cycloaddition can occur via either a concerted pathway or a stepwise reaction, diradical pathway.
19.
It is currently generally accepted that the Cope rearrangement follows an allowed concerted route through a homoaromatic transition state and not a diradical.
20.
A major difficulty of [ 2 + 2 ] photocycloadditions is the possibility of side reactions associated with the diradical intermediate or excited enone.
