[MrHappy0]

Why is triton B a good base for Aldol condensation RXN? I assume it is because the Nitrogen ion is sterically hindered an won't react without anything.

Also, why is it generally important to add the base at 100celsius. I assume this is because this is the energy required to eliminate water during condensation but this seems like a weak explanation

[jake.n]

The only reason I can think to do this reaction at 100C is to boil off water and drive the reaction to completion.  If your solvent is immiscible, I don't think this is necessary, as the water is excluded from the reaction as it proceeds.  What solvent are you working with?

[nox]

Re Triton B:

It's an organic soluble form of hydroxide, although truth be told it's not something I'd personally consider using for an aldol unless it was on really simple/activated substrates.

[MrHappy0]

Well, it was synthesis of tetraphenylcyclopentadienone from benzil and dibenzylketone in triethylene glycol (solvent).

So triton B was used because it is organic soluble. NaOH would not be as effective because it is less soluble in organic solutions?

[Honclbrif]

Was this for an o-chem lab course? I suspect that the reason why triton-b was used is because it is soluble in organics and, more importantly, easy to handle.

In most lab settings, if you want to generate an enolate, the reagent you reach for is LDA [http://en.wikipedia.org/wiki/Lithium_diisopropylamide]. However, as it is a rather sensitive reagent, its not really one which the profs would be handing out learners. I think the triton serves the dual purpose of demonstrating that this enolate voodoo is really real upon a simple substrate, and keeping the course's budget down.

[Honclbrif]

To clarify the original question: the nitrogen in the triton is in the form of a quaternary ammonium ion, and is not basic in the least. In fact, if anything, it probably counts as a Lewis acid, due to the positive charge. It is the hydroxide counterion which is acting as a base.

[MrHappy0]

Awesome! I posted this a while back and have been acquainted with LDA now. Yes, it is an O-Chem class at UVM.

To clarify the original question: the nitrogen in the triton is in the form of a quaternary ammonium ion, and is not basic in the least. In fact, if anything, it probably counts as a Lewis acid, due to the positive charge. It is the hydroxide counterion which is acting as a base.

-Thank you for the clarification. I know that the hydroxide is responsible for the formation of the enolate. I was just asking if the quaternary ammonium ion was not compatible (reactive) with anything in solution.

[matt85]

Also, why is it generally important to add the base at 100celsius. I assume this is because this is the energy required to eliminate water during condensation but this seems like a weak explanation

The heat is required to push the alpha-beta hydroxyketone (addition product) to the alpha-beta unsaturated ketone (condensation product.)

Heat is not required when the product formed can conjugate w/ pi orbitals other than those of the respective carbonyl.

[MrHappy0]

Thanks matt85! The one section I need to overlook is conjugation. I tend to miss those points often.