naming bridgehead carbons

Nomenclature of spiro compounds


            Compounds in which one carbon atom is common to two different rings are called spiro compounds. The IUPAC name for a spiro compound
begins with the word spiro followed by square brackets containing the number of carbon molecules, in increasing order, in each ring connected to the common carbon atom and then by the name of the parent hydrocarbon corresponding to the total number of the carbon atoms in the two rings. The position of substituents are indicated by numbers ; the numbering beginning with the carbon atom adjacent to the spiro carbon and proceeding first around the smaller ring and then to the spiro atom and finally around the larger ring For example,

then  to the spiro atom and finally around the larger ring.

 For example,