Is Crossed Aldol Condensation of Acetone and Ethyl Methyl Ketone Possible?

[baldbrain]

Is the crossed aldol condensation of acetone and ethyl methyl ketone possible?

 

[TeethWhitener]

Sure, why not? I couldn't tell you the optimal reaction conditions, but no doubt it's possible.

 

[baldbrain]

Sure, why not? I couldn't tell you the optimal reaction conditions, but no doubt it's possible.

I just need to know if the usual alkaline conditions are enough

 

[TeethWhitener]

It's enough for acetone self-condensation. My guess is that the alpha hydrogen in MEK is the same to somewhat more acidic than in acetone, so the equilibrium mixture might favor the crossed product. But I don't know for certain. If I were you, I would do a lit search on the desired products if you're concerned about yield.

Edit: Here's a procedure for acetone self-condensation that may be illustrative:
http://www.orgsyn.org/demo.aspx?prep=cv1p0199
They use barium hydroxide as the base but mention that alkali hydroxides (e.g., NaOH) work also.

 

[baldbrain]

My guess is that the alpha hydrogen in MEK is the same to somewhat more acidic than in acetone, so the equilibrium mixture might favor the crossed product.

Hey, but MEK has 2 α carbons, so which α hydrogen are you talking about?

 

[TeethWhitener]

Is this a homework assignment? It'll be the one with the most stable enolate. You can use Zaitsev's rule as a guide here.

 

[baldbrain]

I know the Saytzeff rule. So, that -CH2- hydrogen will preferentially take part in the condensation. But how that speak about acidity?

 

[baldbrain]

But how that speak about acidity?

Oh wait, I got it. Since, the enone formed from the -CH2- is more stable, that carbon shall get deprotonated quickly and hence that α hydrogen will be more acidic.

 

[TeethWhitener]

Sounds good.

 

[baldbrain]

Sounds good.

Thanks