Theory:Nomenclature:Circular Hydrocarbons

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Rule #1: Denote cyclo- with the cent sign.

Rule #2: Center symbols (the C and the cent signs so far) can only be omitted if either no atoms are being added (discussed later) or if it is a C and forms the first chain (before the first pipeline character).


The cyclo is denoted with the cent sign. Unlike the original C for straight chain hydrocarbons, this cannot be omitted.

Linked Strings

Rule #3: Linked carbon strings (branches of carbon attached to other branches at both ends) have C as the center symbol (unless it's not carbon), the superscript after it denoting number of atoms in the string, the subscript before it denoting the former atom # it is attached to, and the superscript before it denoting the latter atom # it is attached to.

Rule #4: When adding a linked carbon string, the added carbons are numbered in increasing numerical value from the former atom # (subscript) to the latter atom # (superscript).


Branches linked at both ends are given a subscript and a superscript referring to the connected atom #'s.


There is always one cyclo main. The others are linked onto what comes before them.


Rule #5: Benzene is represented by z and never has a superscript after it. The z cannot be omitted, even if it comes first in the name.


Benzene's central character is a z and cannot be omitted.

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