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I'm looking in a textbook at an asphaltene molecule. enter image description here

The two aromatic rings next to the Nitrogen are shaded. What does that mean? I think the Nitrogen's create delocalized electrons in this configuration, so maybe the shaded circle is the range over which that free radical is delocalized?

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    $\begingroup$ This is not a universally accepted notation. $\endgroup$ – Ivan Neretin Nov 13 '20 at 21:16
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    $\begingroup$ So it means "Ooh, I made a pretty picture!" $\endgroup$ – Oscar Lanzi Nov 13 '20 at 21:21
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    $\begingroup$ The open circles of course represent aromatic rings, however this is no now the accepted drawing. The accepted way is to draw out the double bonds. // I'd guess that the solid circles are for heterocyclic aromatic rings. $\endgroup$ – MaxW Nov 13 '20 at 21:38
  • $\begingroup$ Dunno, there is a hetrocylic ring with sulfur that doesnt get the solid circle. I've tried contacting the authors but this was long time ago: Gafanova O.V.,Yarranton W. (2001) The Stabilization of Water-in-Hydrocarbon Emulsions by Asphaltenes and Resins, J. Colloid Interf. Sci. 241, 469-478. .... IGNORE! I've found Professor Yarranton. $\endgroup$ – Tunneller Nov 13 '20 at 22:33
  • $\begingroup$ @Tunneller The sulfur ring isn't unsaturated so doesn't really count as an exception. $\endgroup$ – matt_black Nov 14 '20 at 1:07

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