can keto-enol tautoermization occur without catalyst?

[imapremed]

do you specifically need a catalyst? or can a ketone and enol tuatoerizme without a catalyst (but just take longer to reach equilibrium if we start from just say the ketone form - cuz the forward reaction is slower to start up)

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[whiteshadodw]

do you specifically need a catalyst? or can a ketone and enol tuatoerizme without a catalyst (but just take longer to reach equilibrium if we start from just say the ketone form - cuz the forward reaction is slower to start up)

generally speaking, keto enol tautomerization can occur in say, water, or something else. it actually happens all the time (frequently enough to where if we didn't have proofreading activity in our polymerase we'd be screwed) during DNA replication.

but its really not that frequent, i think its like 999:1 or something ridiculous. but if you're replicating millions or billions of base pairs, it matters.

 

[gunj122]

a catalyst just speeds up a reaction. that's its sole purpose. it's not like a gate or something to allow the reaction to happen or not. with or without a catalyst, in any reaction, the reaction will occur. the difference lies in the time it takes to reach equilibrium.

 

[Nymphicus]

yes

 

[imapremed]

k makes sense! was just verifiying stuff- so just less particles will have the energy to go over the activation energy... but as always SOME lucky little particles will have the energy to collide with something else and make a product

now... is the following correct:
if we were at say absolute zero, there is not kinetic energy (besides the quantum electron spin energy that keeps the molecules as molecules and not atoms) for the atoms to collide and thus on a boltzman distribution the probabilty to collide = 0 (same crap as arrhenius equation) and so no reaction?

 

[gunj122]

k makes sense! was just verifiying stuff- so just less particles will have the energy to go over the activation energy... but as always SOME lucky little particles will have the energy to collide with something else and make a product

now... is the following correct:
if we were at say absolute zero, there is not kinetic energy (besides the quantum electron spin energy that keeps the molecules as molecules and not atoms) for the atoms to collide and thus on a boltzman distribution the probabilty to collide = 0 (same crap as arrhenius equation) and so no reaction?

yup, zero kelvin means zero rate constant from the Arrhenius equation. atomic kinetic energy is required to proceed through a reaction.

 

[salim271]

Keto form can turn to enol form in solution, but at equilibrium there will be very few enol form molecules because the keto form is many times more stable. The only way the keto form would be driven to the enol form is if there was some reason that the enol form would be more stable, or the reaction was manipulated using Le Chatlier's principle.

I can only really think of two examples where enol form is formed in high amounts. The Claisen rearrangement (where the enol form is driven by the stability that's gained by reforming the benzene ring, taking away the ketoform's oxygen pi bond) and the tautamerization of the glucose (enol form) from fructose (keto form) that happens spontaneously in solution.