1.2 Cyclic Systems
35
isomers, a numerical descriptor enclosing in square brackets the sums of
C atoms present in each branch is placed between the term spiro and the
rest of the name. This could be construed as inconsistent because, contrary
to the rules for bridged systems, the smaller branch is cited first. If double
bonds are present they are given lowest possible locants as usual.
6
7
[J
Spiro [3.5]nona-l,5,7 -triene
Linear polyspiro compounds of this kind are identified as dispiro-,
trispiro- etc. -alkanes; here too the numerical descriptors are obtained by
enclosing the sums of atoms between the spiro centers in square brackets
and separating them by full stops. The smaller peripheral ring is numbered
first, and smaller numbers are preferred for the internal path lengths. This
leads automatically to smallest possible locants for spiro centers when
overall numbering starts on the smaller outer ring at a C atom next to the
first spiro junction.
12
Dispiro[5.1.7.2]heptadeca-9,16dien-12-yne
~:
7
4
Trispiro[2.2.1.3.2.2]
pentadecane
To permit their distinction from related linear isomers the descriptors of
branched spiro compounds must be supplemented at least by the locants
of the branching spiro centers which are added as superscripts to the corresponding branching denominators.
12
15
11
~
1
10
9
6
3
2
Trispiro [2.2.2 6 .2.2 11 .2 3 ] pentadecane
The former name trispiro[2.2.2.2.2.2]pentadecane was identical with
that of the linear isomer shown to the right, whose numerical descriptor
can also be made more accurate by using the format ... [2.2.2.2 9 .2 6 .2 3 ] ••••
35
isomers, a numerical descriptor enclosing in square brackets the sums of
C atoms present in each branch is placed between the term spiro and the
rest of the name. This could be construed as inconsistent because, contrary
to the rules for bridged systems, the smaller branch is cited first. If double
bonds are present they are given lowest possible locants as usual.
6
7
[J
Spiro [3.5]nona-l,5,7 -triene
Linear polyspiro compounds of this kind are identified as dispiro-,
trispiro- etc. -alkanes; here too the numerical descriptors are obtained by
enclosing the sums of atoms between the spiro centers in square brackets
and separating them by full stops. The smaller peripheral ring is numbered
first, and smaller numbers are preferred for the internal path lengths. This
leads automatically to smallest possible locants for spiro centers when
overall numbering starts on the smaller outer ring at a C atom next to the
first spiro junction.
12
Dispiro[5.1.7.2]heptadeca-9,16dien-12-yne
~:
7
4
Trispiro[2.2.1.3.2.2]
pentadecane
To permit their distinction from related linear isomers the descriptors of
branched spiro compounds must be supplemented at least by the locants
of the branching spiro centers which are added as superscripts to the corresponding branching denominators.
12
15
11
~
1
10
9
6
3
2
Trispiro [2.2.2 6 .2.2 11 .2 3 ] pentadecane
The former name trispiro[2.2.2.2.2.2]pentadecane was identical with
that of the linear isomer shown to the right, whose numerical descriptor
can also be made more accurate by using the format ... [2.2.2.2 9 .2 6 .2 3 ] ••••