Oxygen Charge & Electron Density in Simple Carboxylic Acids

In summary, the oxygen atoms in a simple carboxylic acid are equivalent in terms of negative charge and electron density due to resonance and the ability of the carboxylic group to freely rotate around a single bond. In the mechanism of esterification, the proton can attach to either oxygen due to the acidic environment, but the final product will be the same due to the ability of the group to rotate. The acidic Fischer esterification involves a doubly protonated carboxyl group, with both oxygens becoming protonated and the carbocation being attacked by a nucleophile. For more information, please see the link provided.
  • #1
Karan Punjabi
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In any simple carboxylic acid there are two oxygen atoms then i have a confusion that which oxygen has more negative charge on it or which one has the most electron density on it?
 
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  • #2
They are equivalent due to resonance, plus the carboxylic group freely rotates around the single bond - so it doesn't matter.
 
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Likes Karan Punjabi
  • #3
Borek said:
They are equivalent due to resonance, plus the carboxylic group freely rotates around the single bond - so it doesn't matter.
But in mechanism of esterification in presence of an acid...the proton attacks tje double bonded oxygen
 
  • #4
Once the carboxylic group becomes protonated (in other words: is not dissociated) it is no longer symmetrical (no resonance). Which oxygen becomes protonated is in most cases completely random. But it still doesn't matter to which oxygen the H is attached, as the group can freely rotate around "carbon-rest of the molecule" bond, so the final product will be exactly the same.
 
  • #5
I'm assuming you're talking about acidic Fischer esterification, but it's hard to tell from your question what step is tripping you up. Since the environment is acidic, the carboxyl is going to be overwhelmingly neutral. However, the key intermediate in the reaction is a doubly protonated carboxyl group. Both oxygens become protonated and the two OH groups attached to the carboxyl carbocation draw a lot of electron density away from this carbon. The carbocation therefore has a significant partial positive charge which is readily attacked by a nucleophile (in the case of esterification, the nucleophile is the oxygen on a hydroxyl group). The link below gives a good overview:

http://www.organic-chemistry.org/namedreactions/fischer-esterification.shtm

The carbocation intermediate that I referred to is given by the resonance structure in the first set of brackets.
 

1. What is Oxygen Charge?

Oxygen charge refers to the electric charge that is present on the oxygen atom in a molecule. This charge is determined by the difference in electronegativity between the oxygen atom and the other atoms it is bonded to. Oxygen is highly electronegative, meaning it has a strong attraction for electrons, so it often carries a partial negative charge in a molecule.

2. How is Oxygen Charge related to Electron Density?

Oxygen charge and electron density are closely related. The higher the oxygen charge, the greater the electron density around the oxygen atom. This is because the negative charge on the oxygen attracts more electrons, resulting in a higher electron density around the atom. Conversely, a lower oxygen charge corresponds to a lower electron density around the oxygen atom.

3. What is the role of Oxygen Charge & Electron Density in Simple Carboxylic Acids?

In simple carboxylic acids, the oxygen atom is part of a carboxyl group (-COOH), which is responsible for the acidic properties of these compounds. The oxygen charge and electron density play a crucial role in determining the strength of the acid. A higher oxygen charge and electron density result in a stronger acid, as the negative charge on the oxygen atom makes it easier for the molecule to release a hydrogen ion (H+).

4. How do Oxygen Charge & Electron Density vary among different Carboxylic Acids?

The oxygen charge and electron density can vary among different carboxylic acids depending on the number and types of substituents attached to the carboxyl group. For example, a carboxylic acid with more electronegative substituents (such as a halogen) will have a higher oxygen charge and electron density compared to one with less electronegative substituents.

5. How can Oxygen Charge & Electron Density be experimentally determined in Carboxylic Acids?

Oxygen charge and electron density can be experimentally determined through various methods, including nuclear magnetic resonance (NMR) spectroscopy, X-ray crystallography, and computational studies. These techniques allow for the measurement or calculation of the electron density distribution around the oxygen atom in a carboxylic acid molecule.

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