A radical that carries an
electric charge. A positively charged radical is called a '
radical cation' (e.g. the benzene radical cation
C6H6.+
); a negatively charged radical is called a '
radical anion' (e.g. the benzene radical anion
C6H6.ā
or the benzophenone radical anion
Ph2CāO.ā
).
Commonly, but not necessarily, the odd electron and the charge are associated with
the same atom. Unless the positions of unpaired spin and charge can be associated
with specific atoms, superscript dot and charge designations should be placed in the
order
.+
or
.ā
suggested by the name '
radical ion'. (e.g.
C3H6.+
).
Note:
In the previous edition of this Compendium, it was recommended to place the charge
designation directly above the centrally placed dot. However, this format is now discouraged
because of the difficulty of extending it to ions bearing more than one charge, and/or
more than one unpaired electron. In mass spectroscopic usage the symbol for the charge
precedes the dot representing the unpaired electron.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1156
PAC, 1995, 67, 1307
(Glossary of class names of organic compounds and reactivity intermediates based on
structure (IUPAC Recommendations 1995))
on page 1363