Aldol condesation

[GArjcc]

Hi,

I was carrying out an aldol reaction with 2'-hydroxyacphenone and 4-methythiobenzaldhye with KOH in methanol there was no reaction after beeing left over night . I then repeated the reaction at with heat and reflux and again no reaction. When i carried the reaction out with NaOH in ethanol with heat and reflux  it had  worked. 

Is there any reason for the reaction not to work with KOH and methanol as the reagent ?

Thanks

[ARN321]

Ethanol is best solvent for aldol condensation.

Temperature is also important. When reaction takes place at RT, the aldol addition product is produced. At 50C, the aldol condensation product is isolated..

[BrandyN11]

Hi,

I read your issue and I have a suggestion for this. The aldol reaction might not proceed with KOH in methanol due to the pKa of the 2’-hydroxy group being around 9, which deprotonates readily to alcoholic hydroxide. For the reaction to work, a second deprotonation at the methyl group is needed to form the enolate anion.

This is more likely to occur with NaOH in ethanol, possibly due to better solvation effects and the higher acidity of ethanol compared to methanol.

I hope my suggestion will be helpful for everyone. If you have any query then tell me.