If the nucleophiles have almost same size (not a large difference) such as $\ce{C- , N- , O-}$ then how their nucleophilicty varies in protic and aprotic solvents?\

Does it depend on types of reaction such as Sn1 or Sn2 ?


closed as too broad by Mithoron, Tyberius, aventurin, Todd Minehardt, Gaurang Tandon May 12 '18 at 3:50

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  • $\begingroup$ I suggest coming up with more descriptive titles for your two questions, right now they look very generic and if I did not click to check I would have thought you posted the same thing twice. $\endgroup$ – orthocresol May 11 '18 at 14:40

From what I learned in organic I, their nucleophilicity does not change with the solvent because if the solvent is polar Protic, each nucleophile will be hindered in a similar manner (due to the solvent cage). If the solvent is polar aprotic, this hindrance does not matter. In both cases, nucleophilicity matches base strength.

I believe the solvent only affects nucleophile strength going down the periodic table. There are also polarizability effects for larger molecules but I’ve been told in general, a smaller molecule is a stronger nucleophile and larger molecules are weaker in aprotic solvents. This trend reverses for polar Protic solvents.

Also keep in mind, the strength of the nucleophile only matters for SN2 because of the backside attack being the slow step.

  • $\begingroup$ This answer is not correct because solvation is infinitely more complicated than what you're claiming here. There will certainly be an effect though determining what that is is certainly not straightforward. $\endgroup$ – Zhe May 11 '18 at 13:49
  • $\begingroup$ I’m sure it is more complicated. I just wanted to suggest what I learned in my organic I class even though I’m sure it was over simplified as is most material that I have learned. $\endgroup$ – Dylan Patel May 11 '18 at 13:52
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    $\begingroup$ @Zhe can you please explain it ? $\endgroup$ – INter May 11 '18 at 14:50

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