The Inductive Effect and Electronegativity

In summary: According to my A level Chemistry textbook, the presence of the O atom in a C=O bond in any carboxylic acid (CH3COOH, for instance) pulls the electrons towards it causing the O-H bond to "weaken", thereby making the molecule more susceptible to dissociation, or in other words, accounts for the "acidity" of carboxylic acids. This weakening of the bond leads to an even more polar O-H bond, which in turn accounts for the decrease in bond energy.
  • #1
PFuser1232
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According to my A level Chemistry textbook, the presence of the O atom in a C=O bond in any carboxylic acid (CH3COOH, for instance) pulls the electrons towards it causing the O-H bond to "weaken", thereby making the molecule more susceptible to dissociation, or in other words, accounts for the "acidity" of carboxylic acids.
If i am not wrong, the act of pulling electrons away from the O-H bond would give rise to an even more polar O-H bond. What eludes me is how this accounts for a decrease in bond energy. As a matter of fact, when I apply the somewhat simple (considering the number of variables involved in such a situation) case of Coulomb's law for two point charges, it appears to me this separation of charges would make the bond all the stronger.
Can someone please point out to me where I'm going wrong with this? Perhaps the O-H bond does become stronger as a result of the negative inductive effect mentioned earlier in the post, but becomes more prone to the tendency of H2O to separate cations and anions? So the bond doesn't become weaker per se, and just becomes more "prone to dissociation"? I am lost.
 
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  • #2
Carboxylic acid acidity is better explained by resonance structures of the anion produced by deprotonation. The negative charge can resonate between both oxygens thus lowering the charge density and stabilizing the anion. I'm not sure if that is what the book explanation is trying to get at but in general resonance effects are much stronger than inductive effects. Perhaps posting the relevant text verbatim can help us help you interpret the book explanation better.
 
  • #3
Yanick said:
Carboxylic acid acidity is better explained by resonance structures of the anion produced by deprotonation. The negative charge can resonate between both oxygens thus lowering the charge density and stabilizing the anion. I'm not sure if that is what the book explanation is trying to get at but in general resonance effects are much stronger than inductive effects. Perhaps posting the relevant text verbatim can help us help you interpret the book explanation better.

I'm glad you brought this up. The book does make a reference to this concept as well (and it makes perfect sense to me), but as a separate point. The other point deals with the acid in and of itself wheras this point deals with the conjugate base, namely CH3COO-. The book lists the two ideas separately and independently.
 

1. What is the Inductive Effect?

The Inductive Effect is a phenomenon in which the electronegativity of nearby atoms affects the distribution of electrons in a molecule. This can result in the polarization of bonds, making one end of the bond more negative and the other end more positive.

2. How does the Inductive Effect affect the polarity of a molecule?

The Inductive Effect can increase or decrease the overall polarity of a molecule, depending on the electronegativity of the atoms involved. If the inductive effect causes the electrons to be pulled towards a more electronegative atom, the molecule will become more polar. If the effect pulls the electrons towards a less electronegative atom, the molecule will become less polar.

3. What is the relationship between Inductive Effect and Electronegativity?

The Inductive Effect and Electronegativity are closely related because the electronegativity of an atom determines its ability to pull electrons towards itself. Atoms with higher electronegativity have a stronger inductive effect on nearby atoms, causing the distribution of electrons in a molecule to be more polarized.

4. How does the Inductive Effect impact the reactivity of a molecule?

The Inductive Effect can significantly impact the reactivity of a molecule by influencing the distribution of electrons in chemical bonds. It can make certain atoms or functional groups more electron-rich or electron-deficient, making them more or less reactive towards other molecules or chemical species.

5. Can the Inductive Effect be observed experimentally?

Yes, the Inductive Effect can be observed experimentally through various techniques such as nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, and X-ray crystallography. These techniques allow scientists to study the distribution of electrons in a molecule and determine the presence and strength of the inductive effect.

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