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I have studied that as electronegativity increases nucleophilicity decreases. But in the aprotic solvent the order of nucleophilicty is: $$\ce{F- > Cl- > Br- > I-}$$ but how is this possible as $\ce{F-}$ is strongly electronegative as well as a strong nucleophile Isn't this contradictory? There is no effect of the aprotic solvent on anions.

Information given : This causes the most confusion, because it is solvent-dependent. In polar protic solvents (e.g. water and alcohols, any solvent with OH) nucleophilicity increases as you go down the periodic table (F- < Cl- < Br- < I – ). In polar aprotic solvents (e.g. DMSO, acetone) the order is reversed, and the most basic nucleophiles are also the most nucleophilic. (F- > Cl – > Br – > I – ).

On https://www.masterorganicchemistry.com/tips/what-makes-a-good-nucleophile/

I want to know why my concept is wrong.

INter
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  • Just to make sure I understand: did you just claim that iodide is not the best nucleophile in that series? – Zhe May 11 '18 at 13:04
  • @Zhe yes I am claiming that in aprotic solvent . – INter May 11 '18 at 14:41
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    Where did you see the information suggesting this trend? This is counter to my understanding, and I'm guessing it is counter to many others' understanding here based on Zhe's response. – SendersReagent May 11 '18 at 15:13
  • @SendersReagent https://www.masterorganicchemistry.com/tips/what-makes-a-good-nucleophile/ – INter May 11 '18 at 16:17
  • @Zhe http://chemistry.umeche.maine.edu/CHY251/Ch7-Overhead4.html – INter May 11 '18 at 16:17
  • The short answer to your question is that your question doesn't make sense. Electronegativity is the property of an atom (e.g., fluorine). You can't talk about the electronegativity of your halide. The tendency of the neutral atom to pick up an electron is not the same thing as the anion sharing a pair of electrons. – Zhe May 11 '18 at 17:57
  • @Zhe on this site https://www.masterorganicchemistry.com/2012/06/18/what-makes-a-good-nucleophile/ they have shown dependence of nucleophile with electronegativity . – INter May 11 '18 at 18:12
  • Yes, but the terminology is loose. You should not refer to the electronegativity of a halide. – Zhe May 11 '18 at 18:28
  • @Zhe Can you please explain me why my concept is wrong ? – INter May 11 '18 at 18:31
  • Which one? There's a big block of text... – Zhe May 11 '18 at 20:12
  • @Zhe how is this possible as F− is strongly electronegative as well as a strong nucleophile Isn't this contradictory? – INter May 12 '18 at 02:03
  • There a lot of wrong with this statement. Nucleophilicity is a kinetic concept and electronegativity is a thermodynamic concept. It doesn't make sense to compare these two concepts. Also, you're comparing the property of an neutral atom, electronegativity of fluorine, with the property of a anion, nucleophiliticity of fluoride. That also makes no sense. – Zhe May 12 '18 at 16:44

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