Arrows radical reaction representation

Fig. 4 Schematic representation of long-distance radical cation migration in DNA. In AQ-DNA(l), irradiation of the anthraquinone group linked at the 5 -terminus leads to reaction at GG steps that are 27 A and 44 A from the site of charge injection. The amount of reaction observed at each guanine is represented approximately by the length of the solid arrow. In UAQ-DNA(2), irradiation of the anthraquinone leads to reaction at each of the eight GG steps. However, replacement of a G by 7,8-dihydro-8-oxoguanine (8-OxoG) introduces a deep trap that inhibits reaction at guanines on the same side of the DNA as the trap...

SCHEME 8.R.5 Representations of some reactions involving bond breaking and bond making using curved arrows (a) a radical s addition to a double bond, (b) an ionic displacement... 

Scheme 9.101. A representation of the Hnnsdiecker reaction of the silver salt of propanoic acid. It is generally accepted that the precipitation of silver bromide (AgBr) is accompanied by formation of an acylhypobromite and the homolysis of the oxygen bromine bond generates a bromine atom and the carboxyl radical. The arrows shown on the carboxyl radical (with half-heads) are drawn to account for the apparent movement of one electron (in contrast to the usual cartoons showing two electron arrows ) at a time to produce carbon dioxide (CO2) and the ethyl radical (CH3CH2 ). The latter reacts with bromine to yield bromobutane (CHsCHjBr).

When drawing mechanism arrows to show cleavage reactions it is convenient to choose a localized representation of the radical cation, as we have done above for propane. (When showing only an equation for the cleavage and not a mechanism, however, we would use the convention of brackets around the formula with the odd electron and charge shown outside.) Fragmentation equations for propane would be written in the following way (note... 

---