December 07, 2022, 05:53:39 AM
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Topic: Electron withdrawing and electron donating groups.  (Read 1720 times)

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Offline confusedcollegestudent

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Electron withdrawing and electron donating groups.
« on: July 08, 2017, 02:07:58 PM »
I just want to make sure that I'm understanding EWG and EDG right.
An EWG will pull electron density AWAY from the rest of the molecule. They're usually more electronegative atoms and by doing that, the molecule will increase in acidity AND the conjugate base will be resonance stabilized. From the increased stability, the molecule also becomes more reactive.
In the case of EDG, the molecule will decrease in acidity and reactivity because they will GIVE its own electrons to the rest of the molecule.
Is this correct? This is my understanding of how these groups work, I just want to make sure that it's accurate.

Offline clarkstill

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Re: Electron withdrawing and electron donating groups.
« Reply #1 on: July 10, 2017, 10:09:17 AM »
I just want to make sure that I'm understanding EWG and EDG right.
An EWG will pull electron density AWAY from the rest of the molecule. They're usually more electronegative atoms and by doing that, the molecule will increase in acidity

yes

AND the conjugate base will be resonance stabilized.

not necessarily - not all EWGs operate by resonance (e.g. CF3 groups)

From the increased stability, the molecule also becomes more reactive.

That entirely depends what it's reacting with and what you're comparing it to. For example, NO2 is an EWG, so nitrobenzene is more electron deficient than benzene, and therefore more reactive with nucleophiles than benzene. Conversely, it is very unreactive with electrophiles, much less so than benzene.

The complementary argument holds for EDGs - they make a molecule more reactive with electrophiles, and less reactive with nucleophiles.

Hope this helps.

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