6.4 Numbering
181
If the most senior group appears both in the cyclic and in the catenic
parent component, that unit serves a reference structure which carries the
largest number of these groups. If, however, the number of highest ranked
groups is identical for both components the instructions of Section
1.2.1.2.5 must be consulted, according to which that component is preferred which exhibits the highest degree of substitution or the largest
number of atoms. Chern. Abstr. in such situations proceeds more consistently insofar as rings are always awarded higher priority than chains.
6.4
Numbering
As a consequence of the presence of functional groups, the numbering
rules for parent systems must also be supplemented in a number of essential points. As far as the numbering regulations of Sections 1.1 and 1.2 still
leave a choice, subsequent assignment of lowest locants is decided according to the following criteria examined sequentially:
a) indicated hydrogen (even if not denoted explicitly),
b) free valence,
c) highest ranked characteristic group expressed in suffix form,
H H
4-Aminocyclohex -2-en-I-ol
8-Carboxy-4H-fluoren-5-yl
d) multiple bonds altogether, then double bonds,
O
HCI
4
H
1_2
3
CI
3,4-Dichlorocyclohex -I-ene 3,7-Dinitrocyclooct-I-en -5-yne
e) lowest locants for all prefix substituents, (detachable) hydro prefixes,
"ene"and "yne"positions considered together,
181
If the most senior group appears both in the cyclic and in the catenic
parent component, that unit serves a reference structure which carries the
largest number of these groups. If, however, the number of highest ranked
groups is identical for both components the instructions of Section
1.2.1.2.5 must be consulted, according to which that component is preferred which exhibits the highest degree of substitution or the largest
number of atoms. Chern. Abstr. in such situations proceeds more consistently insofar as rings are always awarded higher priority than chains.
6.4
Numbering
As a consequence of the presence of functional groups, the numbering
rules for parent systems must also be supplemented in a number of essential points. As far as the numbering regulations of Sections 1.1 and 1.2 still
leave a choice, subsequent assignment of lowest locants is decided according to the following criteria examined sequentially:
a) indicated hydrogen (even if not denoted explicitly),
b) free valence,
c) highest ranked characteristic group expressed in suffix form,
H H
4-Aminocyclohex -2-en-I-ol
8-Carboxy-4H-fluoren-5-yl
d) multiple bonds altogether, then double bonds,
O
HCI
4
H
1_2
3
CI
3,4-Dichlorocyclohex -I-ene 3,7-Dinitrocyclooct-I-en -5-yne
e) lowest locants for all prefix substituents, (detachable) hydro prefixes,
"ene"and "yne"positions considered together,