Resonance Stabilization when electrons can't donate?

[MechRocket]

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!

 

[SpectraCat]

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.

 

[MechRocket]

Thanks very much, SC.

Can you take a look at my other thread too? :)

https://www.physicsforums.com/showthread.php?t=508743