# How to name compounds with more than one spiro atom and cyclic compounds with more than two fused rings?

The nomenclature of the bicyclic and spiro (mono) compounds are easy to understand. But when the number of spiro atoms or the number of rings exceeds 2, the nomenclature turns very complex. I cannot understand the method of numbering the carbons and the method of writing those bracketed numbers with dots and superscripts.

I have read the IUPAC Recommendations 2004, but the text given there is really hard to understand (for me only, I hope). I want to know the method of writing those numbers with the superscripts inside the bracket for spiro and cyclo compounds. Diagrams with arrows or a detailed text with one particular example, will be helpful.

• – user7951 Dec 21 '16 at 14:29
• I have also read the post tagged by @Loong but it only quotes from the IUPAC book, and it is not clear. – Shoubhik R Maiti Dec 22 '16 at 16:15

### Bicyclic compounds

1. Locate the bridgehead carbons, the carbons part of two rings.
2. Now, identify the three connections between the 2 bridgeheads, called bridges: arrange these in decreasing order of number of carbon atoms (excluding the bridgehead). Say these three numbers are m, n, o [m > n > o].
3. Write the name of your compound as: bicyclo[m.n.o]"m+n+o+2"alkane.
4. In case there is a substituent or a functional group is present, you need to number your carbons: start from of the bridge-head, through the longest bridge to the shorter and then the shortest (if any). Other rules of IUPAC apply as such.

### Spirocyclic compounds

1. Locate the bridgehead carbon, the only carbon part of the two rings.
2. Now, spot the two ring systems having having 2 or more carbons: arrange these in increasing order of number of carbon atoms (excluding the bridgehead, again). Say these three numbers are p,q [p < q].
3. Write the name of your compound as: spiro[p.q]"p+q+1"alkane.
4. In case there is a substituent or a functional group is present, you need to number your carbons: start from of the atom next to bridgehead in the smaller ring, through the bridgehead carbon to the bigger ring. Other rules of IUPAC apply as such.

• It appears that you have not understood the question properly. I can understand the naming of bicyclo and mono spiro (i.e. with one spiro atom) compounds; I have asked for the method of naming tricyclo, dispiro, trispiro and other such compounds with more than 2 bridges or spiro atoms. Please modify your answer accordingly. – Shoubhik R Maiti Dec 22 '16 at 16:09
• That really does not answer the question. – Martin - マーチン Nov 21 '17 at 12:28

Spirocyclic compounds: Smaller rings are numbered first, followed by the shorter bridge between the two bridgehead carbons in the middle ring (bridge heads named in this counting itself); the other (longer) bridge of the bridge heads is named last

Named as:

Dispiro[w.x.y.z]alkane

w = number of carbons in the smaller terminal ring x = number of carbons in the smaller bridging ring y = number of carbons in the longer terminal ring z = number of carbons in the longer bridging ring

Tricyclic compounds: Consider naming as a normal bicyclic compound The secondary bridge is named with attachment of locants as superscript, as if it were a normal primary bridge of bicyclic compound

Named as:

Tricyclo[w.x.y.x^m,n]alkane

w = number of carbons in the longest primary ring between main bridgeheads x = number of carbons in the longer primary ring between main bridgeheads y = number of carbons in the primary bridge between main bridgeheads z = number of carbons in the secondary bridge, with the locants of secondary bridge (secondary bridgehead) as superscripts