Acidity of fumaric acid and maleic acid

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Discussion Overview

The discussion centers on the acidity of fumaric acid and maleic acid, exploring the reasons behind the differences in acidity between these two compounds, particularly focusing on their structural configurations and the stability of their respective anions. The conversation includes theoretical considerations and participant inquiries for clarification.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants propose that the cis configuration of maleic acid allows for intramolecular hydrogen bonding, which may stabilize the monoanion through resonance.
  • Others note that while maleic acid has a greater acidity for the first proton, fumaric acid has a more acidic second proton.
  • One participant suggests that the conjugate anion from maleic acid's first dissociation is stabilized by the neighboring acidic group, which de-intensifies the negative charge, but acknowledges that having two neighboring negative anions creates instability.
  • Another participant expresses uncertainty about the acidity comparison between the monoanions of fumarate and malate, suggesting that the presence of a proton on one side of the fumarate may influence its acidity compared to malate.

Areas of Agreement / Disagreement

Participants express differing views on the factors influencing the acidity of fumaric and maleic acids, with no consensus reached on the reasons behind the acidity differences or the stability of the respective anions.

Contextual Notes

Some claims depend on assumptions about resonance stabilization and the influence of neighboring groups, which remain unresolved in the discussion.

dibilo
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hi all, i understand that maleic acid being in cis form is more acidic than fumaric acid.
is it due to the fact that because of the cis configuration, it can form intramolecular H bonds which then stablises the monoanion through resonance or?
then in the monoanion form, furamate monoanion is more acidic than malate monoanion... haha this i have no idea why... can anyone here please give me some guidance? any help would be greatly appreciated =)
 
Last edited:
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can anyone help me please? i am in a total lost T_T
 
The acidity of the first proton is greater for maleic acid, the second proton is not very acidic, fumaric acid has the more acidic second proton.

The conjugate anion formed from the first dissociation is stabilized by the neighboring acidic group for maleic acid, the negative charge is de-intensified. WIth two neighboring negative anions, however, you have a very unstable motif.
 
dibilo said:
hi all, i understand that maleic acid being in cis form is more acidic than fumaric acid.
is it due to the fact that because of the cis configuration, it can form intramolecular H bonds which then stablises the monoanion through resonance or?
then in the monoanion form, furamate monoanion is more acidic than malate monoanion... haha this i have no idea why... can anyone here please give me some guidance? any help would be greatly appreciated =)

Hi
I think the foramate is more acidic because even if there is a delocalise electron but thereis also a proton on the other side which should be taken as a priority, while for malate the proton that in left is busy stabilising the oxygen's negative charge.
 
:smile:
thembi said:
Hi
I think the foramate is more acidic because even if there is a delocalise electron but thereis also a proton on the other side which should be taken as a priority, while for malate the proton that in left is busy stabilising the oxygen's negative charge.
 

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