2.2 Nomenclature Types for Substituted Systems
103
H
HAH
Cycloprop-2-enl-ylium
H
e H
)cl
H
e H
Cyclobut -3-ene1,2-di(ylium)
---&
Cyclopropenylium
,- ,
" 2(£)\
\
,
, -'
Cyclobutenedi(ylium)
H
H
vs.
Ae
H
Cycloprop-len-l-ylium
Particularly for delocalized cations derived from complex heterocyclic
aromatics, significant names can sometimes only obtained with reference
to specifically selected resonance forms.
~N
~D"S P
2,1,3 -Benzothiazaphosphole
eH
0: N'
.'
~
~ ·s·
p" •
2,1,3-Benzothiazaphosphol-l-ium
e
0:)
2,1,3-Benzothiaza -phosphol-7 -ylium
(localized!)
benzothiazaphosphol-3-ylium
H
~.~/
~D~S:
~e
1,2-Dihydro
thiazaphosphol-2-ylium
Intuitively, one is inclined to opt for the formal 10 n-aromatic resonance
form shown on the left.