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Is it possible to have π–π stacking for non-conjugated double bond systems?

For example, can the carbonyl groups of two urea molecules participate in π–π stacking? Although urea prefers to stay in hydrogen bonded form.

I would be really happy if you cite some resources (research paper, book, etc.) while answering.

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  • $\begingroup$ There's quite a conjugation in urea. $\endgroup$ – Mithoron Sep 9 '17 at 19:50
  • $\begingroup$ What you describe would be something very different than ordinary pi-stacking, just like hydrogen bonding is not a simple polar interaction. $\endgroup$ – Karl Sep 9 '17 at 20:03
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    $\begingroup$ en.wikipedia.org/wiki/… $\endgroup$ – Mithoron Sep 9 '17 at 21:50
  • $\begingroup$ @Mithoron I did not want some other type of interaction. I just wanted to know if it possible to have $\pi$ - $\pi$ stacking in non-conjugated systems. $\endgroup$ – Mitradip Das Sep 11 '17 at 6:10
  • $\begingroup$ It is possible in non-aromatic molecules , but p orbitals are needed. See the answer to this question. chemistry.stackexchange.com/questions/60055/… $\endgroup$ – porphyrin Sep 11 '17 at 14:27
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There is a paper titled "Amide-pi interactions between formamide and benzene", doi: 10.1002/jcc.21212. It has been cited by a paper on a crystal structure on a urea transporter (the interaction is between a peptide bond of a ligand and aromatic side chains of the protein).

Technically, the interaction between the arginine side chain and aromatic groups could also fall under your heading, but it is usually described as a cation pi interaction.

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