So a conjugated system is a system of connected p orbitals or alternating single and multiple bonds.

I know that conventionally, we count the number of adjacent parallel p orbitals or alternating single-double bonds to see which molecule is "more conjugated" or not. However, when considering the following molecules: enter image description here I cannot seem to find out which molecule is "more" conjugated or not.

Is there a way to calculate the degree of conjugation? And in this case, would the rhodamine B be the most conjugated compound in the list?

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    $\begingroup$ For a deeper insight on the degree of conjugation, have a look at Clar's rule, for instance: ncbi.nlm.nih.gov/pmc/articles/PMC3982536 $\endgroup$ – Raoul Kessels Dec 3 '19 at 23:25
  • $\begingroup$ Not a "degree" but you can calculate energy of conjugation, $\endgroup$ – Mithoron Dec 4 '19 at 0:21
  • $\begingroup$ There are several but this is a field itself. Note that in complex structure counting how many double bonds are in alternate sequences does not suffice. The first example that comes to my mind is that of antiaromatic cycles. $\endgroup$ – Alchimista Dec 4 '19 at 8:29

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