Acetate anion destabilization by methyl group

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Discussion Overview

The discussion revolves around the concept of destabilization of the acetate anion in acetic acid, exploring the effects of the methyl group and comparing it to other groups like hydrogen and electron-withdrawing groups. Participants seek to clarify the meaning of destabilization, its implications for the acetate ion, and the stabilization mechanisms involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that the methyl group in acetic acid pushes negative charge toward the COO- end, potentially destabilizing the acetate ion.
  • Others argue that electron-withdrawing groups, like CCl3 in trichloroacetic acid, can stabilize the carboxylic acid by pulling negative charge away, which contrasts with the electron-donating effect of the methyl group.
  • A participant questions the definition of destabilization and what occurs when the acetate ion is destabilized, seeking clarity on stabilization processes.
  • One response suggests that destabilization refers to a carboxylic acid's tendency to lose the CO2 group, while another emphasizes that the resonance of the carboxylic acid portion contributes to its stability.
  • Some participants express uncertainty about the structural changes in the anion and whether destabilization leads to any significant alterations in the acetate ion's structure.
  • One participant notes that destabilization is a tautological concept, simply meaning making something less stable, which does not fully address the original question.
  • There is a suggestion that energy differences between the -COOH and -COO- + H+ forms are crucial to understanding stability and dissociation preferences.
  • A later reply indicates that while there may not be structural changes, variations in electron density could lead to minor adjustments in bond lengths and angles.
  • Some participants express frustration over the lack of foundational understanding in the discussion, suggesting that a review of basic chemistry principles may be beneficial.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus on the definition of destabilization or its implications for the acetate ion. Multiple competing views remain regarding the effects of different substituents on stability and the nature of structural changes in the anion.

Contextual Notes

Limitations include a lack of clarity on the fundamental principles of acid-base chemistry and the specific mechanisms of stabilization and destabilization. Some responses rely on assumptions about energy differences and resonance without fully addressing the original questions posed.

hariharan venkatasu
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The alkyl group of acetate ion in acetic acid pushes more negative charge inductively toward already negative COO- end destabilize it.In this context I wish to know what actually is destabilization?What happen when acetate ion is destabilized?How the anion is stabilized ultimately? Could you please explain?
 
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So you are comparing methyl group of acetic acid with Hydrogen of Formic Acid or CO2- of Oxylate? Generally an electron withdawing group like CCl3 (in trichloroacetic acid) pulls negative charge from carboxylic CO2 to the side chain, which allows more Hydrogen ion to detach. Since methyl releases electrons it would make the carboxylic bond with hydrogen stronger. That is methyl makes acetic acid weaker. However an Oxygen, electron withdrawing, makes Carbonic Acid a weak acid, highlighting that electron withdrawing/donating isn't the only criteria. Note that dissociation, acidity, of acetic acid, is in solution with water (The pH definition). Water creates complexes with anions and cation. Rather destabilizing, electron donation allow for more covalent character of acetate compounds eg Copper Acetate.
 
Thank you very much for your reply.But I did not receive reply to my question what actually is destabilization and what happens when acetate ion is destabilized?How stabilization take place ultimately?I request answer for this.
 
Destabilization means a carboxylic acid is prone to losing the CO2 group. Acetic acid is stabilized by methyl group. Trichloroacetic acid easily loses CO2 to become CHCl3. The charge on the carboxylic acid portion of acetic acid resonates between the two oxygens. Because methyl lowers the acidity, hydrogen ions are still attached to one of the oxygens, making them different, sorta, because other acetic acid molecules share hydrogen ions. However this does not destabilize as much as change the resonant structures available. In other words the term "destabilize" does not have anything to do with acetate ions.
 
Thank you very much for the answer which does not fully answer my question
 
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I am very eager to receive your replies to my earlier questions.Could you please help me?
 
It is all about energy differences between -COOH and -COO-+H+. -COO- is stabilized by the resonance - if it has lower electron density it is relatively more stable (has a lower combined energy) and the dissociated form is preferred, the higher the electron density the less the energy "gain" and non dissociated form becomes dominant.

Sadly, I feel like this explanation doesn't answer your question "what is destabilization" - as the only exact answer I can think of is "destabilization is making something less stable", which is rather tautological.
 
Thanks a lot for the answer.But my question is what actually happens to the anion?Is there any structural change to the anion?
Sorry for repeating the same problem.
 
No structural change (although with the changing electron density I wouldn't be surprised by some minor changes to the C-O bond lengths and/or the O-C-O angle).
 
  • #10
Thank you for your answer which clears my doubt to some extent.However I do not understand the first sentence,"It is all about energy differences...and non dissociated form become dominant".Please clarify'
 
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  • #11
I am very eager to see your reply to my last post.I shall be immensely thankful to you if you could post your answer.
 
  • #12
Sorry, every answer we give you leads only to further questions, as if you had no idea what are the basic principles at work. I strongly suggest you read some general chemistry books where these things are explained. I have no problems helping with details, but full lecture on things that are covered in every chemistry course is out of the question.
 
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  • #13
Thanks a lot for the answer and advice.
 

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