On Tue, Oct 23, 2018 at 4:08 PM Peter S. Shenkin <shen...@gmail.com> wrote:
> > - Easily understandable explanation: > - From the Daylight theory manual (and you've used similar > language): *exocyclic double bonds do not break aromaticity.* > - I'd alter this to *double bonds exocyclic to the ring in question > do not break aromaticity*. (I.e., even if they are in other rings) > - Beyond this, conventional electron counting explains everything > in Francis's example and mine. > - > > You're close, but I think there's something missing. Exocyclic double bonds do not prevent an atom from being considered aromatic, but they *may* "steal" a pi-electron - e.g. the C that's double bonded to the O in pyridone contributes zero electrons to the aromatic ring. The challenge here is to define which exocyclic double bonds can do this. For example, you guys are agreeing that the N exocyclic bond next to the boxed C here: [image: image.png] does remove an electron. and, to go all the way in the other direction, what happens here: [image: image.png] And here: [image: image.png] Is that left ring aromatic in all cases? If not, why not? -greg
_______________________________________________ Rdkit-discuss mailing list Rdkit-discuss@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/rdkit-discuss
