Resonance effect on acidity?

[yankswin2011]

I'm having trouble understanding the effect of resonance on acidity?

Specifically, if an acid's conjugate base can be stabalized through resonance (i.e. hydrazine's conjugate base), then it makes the acid more acidic?

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[Lexicon0]

I'm having trouble understanding the effect of resonance on acidity?

Specifically, if an acid's conjugate base can be stabalized through resonance (i.e. hydrazine's conjugate base), then it makes the acid more acidic?

If you think of acid dissociation as a reversible process, it would make sense that the more stable (thermodynamically) a product, the more it's formation will be favored at equilibrium. When resonance stabilizes the conjugate base, the equilibrium will further favor product formation, making an acid more acidic.

Electron-withdrawing groups on an acid have a similar effect. They distribute charge density over a larger area, stabilizing the conjugate base and making the acid more acidic.

Hope this made sense!

 

[yankswin2011]

If you think of acid dissociation as a reversible process, it would make sense that the more stable (thermodynamically) a product, the more it's formation will be favored at equilibrium. When resonance stabilizes the conjugate base, the equilibrium will further favor product formation, making an acid more acidic.

Electron-withdrawing groups on an acid have a similar effect. They distribute charge density over a larger area, stabilizing the conjugate base and making the acid more acidic.

Hope this made sense!

Thanks. Sort of, I'm trying to think of it quantitatively. How about this?

A resonance-stabalized conjugate base is less basic due to resonance stabalization (resonance = increase in stability = decrease in reactivity). Because the conjugate base is "less basic," it's conjugate acid is "more acidic."

 

[GreenRabbit]

Thanks. Sort of, I'm trying to think of it quantitatively. How about this?

A resonance-stabalized conjugate base is less basic due to resonance stabalization (resonance = increase in stability = decrease in reactivity). Because the conjugate base is "less basic," it's conjugate acid is "more acidic."

To be nit picky on the last sentence.. remember that a conjugate base is not the pair of a conjugate acid. i.e. if the conjugate base is OH-, the conjugate acid is H3O+.

 

[orgohacks]

I'm having trouble understanding the effect of resonance on acidity?

Specifically, if an acid's conjugate base can be stabalized through resonance (i.e. hydrazine's conjugate base), then it makes the acid more acidic?

This might help: "5 key trends that influence acidity" http://masterorganicchemistry.com/2010/09/22/five-key-factors-that-influence-acidity/