Does dihydroimidazole (above) exhibit geometrical isomerism? Does the fact that the lone pair is involved in conjugation with a double bond affect anything?

As far as I know, it does not exhibit geometrical isomerism. However, one of my colleagues pointed out that the two nitrogens' lone pairs and hydrogens can adopt cis and trans configuration with respect to each other.

Please provide a detailed explanation. If possible, please also cite your sources.

  • 2
    $\begingroup$ Of course it does show isomerism, like any cyclic compound with different substitutes. (Double bond is irrelevant.) It is just that the isomers can't be isolated because they switch into each other way too easily. $\endgroup$ Apr 28, 2018 at 14:16
  • $\begingroup$ @santimirandarp Hydrogen atoms connect with nitrogens can be cis/trans to each other. This isn't particularly good example, because conjugation with double bond almost flattens amine "pyramids". $\endgroup$
    – Mithoron
    Apr 28, 2018 at 14:37
  • 3
    $\begingroup$ @schrodinger_16 although Mithoron is quite rude, he is right. Nitrogens are somewhere between $sp_2$ and $sp_3$ hybridization. If you look carefully at $sp_3$ nitrogen, you will see that nitrogen's hydrogen can be in cis-trans configuration...(hope to be clear even if I am wrong) $\endgroup$
    – user43021
    Apr 28, 2018 at 15:23


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