[Winga]

pKa of phenol is ~10

PhOH <=> PhO- + H+

Ka = [PhO-][H+]/[PhOH]

logKa = log[PhO-]/[PhOH] + log[H+]

-log[H+] = -logKa + log[PhO-]/[PhOH]

pH = pKa + log[PhO-]/[PhOH]

pH = 10 + log[PhO-]/[PhOH]

When pH < 10,

[PhO-]/[PhOH] < 1

i.e. [PhOH] > [PhO-]

Now, can I say phenol is more thermodynamically stable than phenoxide?

[Garneck]

pKa of phenol is ~10

PhOH <=> PhO- + H+

Ka = [PhO-][H+]/[PhOH]

logKa = log[PhO-]/[PhOH] + log[H+]

-log[H+] = -logKa + log[PhO-]/[PhOH]

pH = pKa + log[PhO-]/[PhOH]

pH = 10 + log[PhO-]/[PhOH]

When pH < 10,

[PhO-]/[PhOH] < 1

i.e. [PhOH] > [PhO-]

Now, can I say phenol is more thermodynamically stable than phenoxide?

Ok, but we we aren't talking about Ph-O- in a base enviroment, now are we?

[movies]

but protonation of phenoxide means destroying the extended pi electron system in the benzene ring, doesnt it?

You would protonate on oxygen, so the benzene pi-system wouldn't be disturbed.

Plus, when you add more electron density into an aromatic system you make it higher in energy.  That's why aromatics with EDGs react faster than those with EWGs in Freidel-Crafts reactions.

[Mitch]

Now, can I say phenol is more thermodynamically stable than phenoxide?

Never EVER EVER EVER EVER can you say that!!!!!!!!!!!!!!!!!

Stability can only be evoked if the two compounds of interest have the exact same number of elements!

I really need to do an article on what it means to be considered stable at some point.

[Winga]

PhOH + H2O<=> PhO- + H3O+   (pKa ~ 10)

What can we also conclude besides the forward and backward reaction rates from this reaction?