A biradical mechanism is also proposed for the formation of certain biomolecules found in marine " sporolides " that have a chlorobenzene unit as part of their structure.
12.
Nevertheless, strained alkyne is a better description of the triple bond nature of ortho-benzyne than biradical ( larger singlet-triplet gap and alkyne-like reactivity ).
13.
"' Butalene "'is a polycyclic hydrocarbon composed of two 1, 4-didehydrobenzene biradical, the valence isomer in which that bridged bond is broken.
14.
In a model system, it was found that the 5, 9-bicyclic core of kedarcidin chromophore exists in equilibrium with the corresponding 5, 5, 6-tricyclic cycloaromatized biradical.
15.
An oxyallyl intermediate or valence tautomer ( formed by cleavage of the C2-C3 bond ) is suggested as the active intermediate or even a biradical structure ( compare to the related trimethylenemethane ).
16.
The rate of pseudo-first-order decay of this model enediyne is highly dependent on the solvent hydrogen-donor ability, indicating that the hydrogen abstraction step following biradical formation is kinetically significant in the cycloaromatization of the enediyne, as opposed to acyclic systems, where formation of the biradical itself is known to be the rate-limiting step.
17.
The rate of pseudo-first-order decay of this model enediyne is highly dependent on the solvent hydrogen-donor ability, indicating that the hydrogen abstraction step following biradical formation is kinetically significant in the cycloaromatization of the enediyne, as opposed to acyclic systems, where formation of the biradical itself is known to be the rate-limiting step.
