Fused and bridged bicycloalkanes

Basic IUPAC Organic Nomenclature

Fused and bridged bicycloalkanes

The root name is based on the total number of C atoms in the ring structures.
The prefix bicyclo[x.y.z] is added where x, y and z correspond to the number of atoms in the "links" as defined below.
The size of the rings is indicated in the square brackets by counting the number of atoms in the links that make each ring, x, y and z, excluding the bridgehead atoms
The number of atoms in the links are listed largest first, i.e. bicyclo[x.y.z] where x > y > z
For substituted bicycloalkanes, the rings are numbered starting at a bridgehead atom and proceeding round the rings, the largest ring first.

If that does not resolve the numbering, then the other rules for determining locants are applied in order (i.e. principal functional group, first point of difference, alphabetisation).

Show bridgehead C
Show C longest link, x
Show C in medium link, y
Show C in shortest link, z

For example, in the structure shown above, the bridgehead atoms are C1 and C6. The three links are x= C2,C3,C4,C5, y = C7,C8 and the final link z has no atoms in it, so this is a [4.2.0] system.

STUDY TIP
In bridged systems, number the biggest ring first
bridged = biggest

Functional group is an alkane, therefore suffix = -ane The ring structure requires the prefix bicyclo The ring structure is C4 therefore root = but The links contain 1, 1 and 0 carbon atoms = [1.1.0] bicyclo[1.1.0]butane
Functional group is an alkane, therefore suffix = -ane The ring structure requires the prefix bicyclo The ring structure is C7 therefore root = hept The links each contain 2, 2 and 1 carbon atom = [2.2.1] bicyclo[2.2.1]heptane
Functional group is an alkane, therefore suffix = -ane The ring structure requires the prefix bicyclo The ring structure is C10 therefore root = dec The links each contain 4, 3 and 1 carbon atom = [4.3.1] bicyclo[4.3.1]decane
Functional group is an alkane, therefore suffix = -ane The ring structure requires the prefix bicyclo The ring structure is C9 therefore root = non The links each contain 3, 3 and 1 carbon atom = [3.3.1] There are two C1 substituents i.e. dimethyl groups First points of difference implies locants are 1,3- 1,3-dimethylbicyclo[3.3.1]nonane