Group actions on molecular graphs

Tests for the existence of molecular graphs become more involved if we admit var- 

24 Remark (Existence of molecular graphs, various valences) There exists at least 

For the existence of a connected molecular graph we need in addition that the following holds  

In the literature we find in this context the notion of double bond equivalent (DBF). The DBF of molecular formula p is 

It is the number by which the number of lines exceeds the minimum required by (Con), i.e. the sum of number of cycles, number of double bonds, and twice the number of triple bonds in a molecule. Conditions (Grl) and (Con) are usually formulated using DBF. For example, conditions (Con) and (Con ) are the same as DBE(/S) 0. 

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