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I can't rationalize why S- is a worse nucleophile than N-. I thought nucelophilicity was related to electronegativity, the more electronegative an atom is, the less of a nucleophile it is. Sulfur is less electronegative than Nitrogen. What concept am I not considering or misunderstanding?

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  • $\begingroup$ Well, if that was so simple... In organic chemistry thinking in terms of electronegativity is hardly enough to guess even acidity. $\endgroup$
    – Mithoron
    Commented Dec 3, 2019 at 21:20

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I think it would be nice to consider the charge density. The S- is more stable than N- because it has more electron shells, so the negative charge density is better distributed in the atom. It makes that the N- is more likely to give up electrons and act as a nucleophile

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  • $\begingroup$ Why wouldn't that apply to oxygen versus sulphur? $\endgroup$
    – ReftPowered
    Commented Dec 3, 2019 at 18:44
  • $\begingroup$ I would swear that the carboxylate can stabilize by resonance and thiolate not $\endgroup$
    – Arnau
    Commented Dec 3, 2019 at 19:08

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