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Topic: Hydrogen bonding or I effect?  (Read 1038 times)

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Offline sharbeldam

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Hydrogen bonding or I effect?
« on: February 05, 2020, 03:10:07 AM »
As much as I love organic chemistry, I dont think it loves me back (Flashback to every girl I've loved) because it always seem to put me in a difficult position with my students that i tutor and I just stare at the question without an answer.

If I'm comparing the acidity of ortho nitrophenol with para nitrophenol, I know that para is more acidic because it has resonance+I effect (ortho too) but ortho-nitrophenol has hydrogen bonding that reduces its acidity and hence ortho is less acidic -> that means that in this case Hydrogen bonding effect> I effect (Since NO2 is closer and withdraws electron more and should stabilize the conjugate base more.)


If I compare ortho flurophenol with para-fluorophenol, same logic but ortho is more acidic because I effect here is stronger than the hydrogen bonding effect.

Is there a rule to know when hydrogen bonding effect is stronger effect than I effect? if the atom is very electronegative like F, the I effect should be stronger, but so does the hydrogen bonding...

I really appreciate the *delete me* thanks.
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Offline rolnor

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Re: Hydrogen bonding or I effect?
« Reply #1 on: February 05, 2020, 04:24:11 AM »
Is there hydrogenbonding in o-fluorophenol? I think not.

Offline sharbeldam

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Re: Hydrogen bonding or I effect?
« Reply #2 on: February 05, 2020, 04:33:55 AM »
Why not? The hydrogen that is connected to phenol oxygen with electron pair on F?
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Offline AWK

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Re: Hydrogen bonding or I effect?
« Reply #3 on: February 05, 2020, 05:05:05 AM »
In crystals, 2-fluorophenol forms hydrogen bonds only between phenolic groups.
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Offline sharbeldam

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Re: Hydrogen bonding or I effect?
« Reply #4 on: February 05, 2020, 05:08:00 AM »
This is not true then? Why?
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Offline AWK

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Offline sharbeldam

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Re: Hydrogen bonding or I effect?
« Reply #6 on: February 05, 2020, 05:28:27 AM »
Everything I have been taught in the past apparently has been a lie.

Appreciate the help.
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Offline AWK

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Re: Hydrogen bonding or I effect?
« Reply #7 on: February 05, 2020, 06:16:56 AM »
Fluoride anion forms very strong hydrogen bonds
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