1.2 Cyclic Systems
43
If these trivial systems are further substituted, however, they are treated as
substituted benzenes.
HC=CH2
1,4-Divinylbenzene
or p-Divinylbenzene
not p-Vinylstyrene
Me
AMe
U Me
1,2,3-Trimethylbenzene
not Methylxylene
not Dimethyltoluene
Pr
AMe
U Me
1,2-Dimethyl3-propylbenzene
(not 3-Propyla-xylene)
In addition to the trivial names already mentioned, a number of more specific group names for arenes with side chains are also retained.
a
a
Benzyl
C6HS-CHzBenzhydryl
(C6HshCHfl
a
fl
a
Phenethyl C6Hs-CHz-CHzStyryl
C6HS-CH=CHy
fl
a
Trityl
(C6HShCCinnamyl
C6HS-CH = CH -CHzNames of polyvalent groups derived therefrom are formed as usual:
Benzylidene C6Hs-CH=
(traditionally also: Benza!)
1.2.2
Heterocyclic Systems
1.2.2.1
Trivial Names
Cinnamylidyne C6HS-CH =CH -C=
There are two reasons why the nomenclature of heterocycles is particularly
complex. First of all, the IUPAC rules are based on two alternative types of
nomenclature which are not very clearly delimited, either in the Ring
Index or in Chemical Abstracts. Secondly, many more trivial names are
retained for heterocyclic compounds than elsewhere. A representative
selection of trivial names, particularly of those widely used as parent