Nucleophilicity/Acidity simple question

[kehlsh]

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Can someone explain why HI is more acidic than HF when I- is more nucleophilic than F-? If I- is more nucleophilic doesn't that mean I- wants to hold H+ tighter, making HI less acidic?

Thanks!

 

[PiBond]

Can someone explain why HI is more acidic than HF when I- is more nucleophilic than F-? If I- is more nucleophilic doesn't that mean I- wants to hold H+ tighter, making HI less acidic?

Thanks!

I- is only more nucleophilic than F- in certain solvents, namely polar protic like water. this is because the F- is small and can therefore be solvated easier whereas I- is large and thus can't be solvated as much. the halides reverse their nucleoplicity trend in protic solvents versus aprotic ones

 

[orgohacks]

Can someone explain why HI is more acidic than HF when I- is more nucleophilic than F-? If I- is more nucleophilic doesn't that mean I- wants to hold H+ tighter, making HI less acidic?

Thanks!

Kobe Bryant is way faster than I am and could easily beat me in a footrace. However, at a cocktail party, Kobe would be surrounded by tons of autograph seekers and other hangers-on, and I could probably get to the dessert tray faster than he could.

Translation:
Fluorine forms strong hydrogen bonds and the solvent shell attenuates its nucleophilicity. Iodine does not form strong hydrogen bonds and moves freely in a protic solvent, making it more reactive in this instance.