Resonance Stabilization when electrons can't donate?

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SUMMARY

Triphenylmethanol exhibits increased acidity compared to ethanol due to the extensive resonance stabilization of its conjugate base's negative charge. The discussion clarifies that the lone pairs on the oxygen atom cannot donate electrons into the aromatic rings, as this would lead to an unstable carbon with five bonds. The Wikipedia entry on triphenylmethanol supports this by indicating no resonance stabilization from the central carbon atom, which is already saturated. Instead, the formation of a carbocation from the protonated form is highly resonance stabilized, leading to increased basicity.

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  • Understanding of acidity and basicity concepts in organic chemistry
  • Knowledge of resonance structures and their implications
  • Familiarity with triphenylmethanol and its chemical structure
  • Basic principles of carbocation stability
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Chemistry students, organic chemists, and educators looking to deepen their understanding of acidity, resonance stabilization, and carbocation behavior in organic molecules.

MechRocket
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A question in ExamKrackers asks us why triphenylmethanol is so acidic. Link to the structure below:

http://en.wikipedia.org/wiki/Triphenylmethanol

Explanation:

Triphenylcarbinol is more acidic than ethanol because it has extensive resonance stabilization of the conjugate base's negative charge.

I'm not seeing how the lone pairs on the Oxygen could donate into any of the rings though. It can't donate those electrons onto the carbon it's next to or else that carbon would have 5 bonds.

Can someone explain? Thanks!
 
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MechRocket said:
A question in ExamKrackers asks us why triphenylmethanol is so acidic. Link to the structure below:

http://en.wikipedia.org/wiki/Triphenylmethanol

Explanation:



I'm not seeing how the lone pairs on the Oxygen could donate into any of the rings though. It can't donate those electrons onto the carbon it's next to or else that carbon would have 5 bonds.

Can someone explain? Thanks!

You are right (again) ... that explanation is simply wrong. In fact, the wikipedia link directly contradicts it, citing precisely the answer you give (i.e. no resonance stabilization since the central C atom is saturated). In fact, the opposite effect (i.e. increased basicity) is expected, since the carbocation formed by elimination of water from the protonated form *IS* highly resonance stabilized.
 

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