Why are there no formal charges on the 1st compound? I am specifically referring to the nitrogen atom, which I would think should exhibit a +2 formal charge? However, in David Klein's organic chemistry textbook it is said that the 1st compound shows no formal charge anywhere. The second compound, of course, exhibits a +1 formal charge on the nitrogen atom and -1 formal charge on the oxygen atom. This would make more sense if I were to take into account the lone pair for Nitrogen in compound 1 (and the 2 lone pairs for oxygen), but then why would they hide the lone pairs in compound 1 and exhibit them in compound 2? Please, correct my incorrect thinking.

Compound 1 and 2

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    $\begingroup$ You're right. In compound 1, you are supposed to assume the lone pairs (note, there are lone pairs on nitrogen, oxygen, and chlorine), but the lone pairs in compound 2 are explicitly drawn. I think you'll find that depending on the exact problem, and what they are trying to test, whether lone pairs are implicit/explicit may not be consistent across the entire book. The book should be consistent within a single problem however, which did not happen here. $\endgroup$
    – jerepierre
    Aug 10, 2015 at 22:35
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    $\begingroup$ Thank you for clarifying the whole situation. I will keep my eyes and mind peeled for these things in the future. $\endgroup$ Aug 10, 2015 at 22:44
  • $\begingroup$ I suspect the lone pairs in compound 2 are shown because this electron configuration is unusual for oxygen in organic compounds. It's possible (I don't have that particular book to check) that this is a convention used throughout. $\endgroup$
    – j_foster
    Aug 11, 2015 at 0:15

1 Answer 1


Drawing common electron pairs like they appear in most organic molecules is only then relevant, when

  • they play a keyrole in the reaction process
  • they should explain a special molecule structure
  • they are of an unusual quantity and thus resulting in a (intermolecular) formal charge

Otherwise especially molecules with a lot of atoms with unpaired electrons (e. g. saccharides) can get confusing. And in addition: they take more time to draw ;) Of course when learning organic chemistry its good to think of them a lot, because of their high reaction potential.

You can be a 100 % sure that when they would not be there in compound 1 that it would be highlighted somehow, because that would result in a very unstable state.


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