[davink67]

why do you add the base in two portions during dibenzalacetone synthesis?
any answer is much obliged!!

[pacifyer]

Weird question... pretty obvious... just follow the instructions carefully.

[davink67]

Thats the question im supposed to answer in my lab report?

[sjb]

What is the actual reaction you did?

[davink67]

It was the claisen-schmidt mixed aldol condensation, 1 equivalent of acetone to 2 equivalents benzaldehyde.

[democanarchis]

What would the product of the reaction be if you added only one equivalent of benzaldehyde and base?

[davink67]

The base is just there to calalyse the reaction surely?

[sjb]

What would the product of the reaction be if you added only one equivalent of benzaldehyde and base?

There is a difference between adding 2 equivalents once, and 1 equivalent each time twice.

Can any other reaction occur between e.g. a strong, concentrated base and a non-enolizable aldehehyde?

[orgopete]

This is a quite interesting question. Without looking up the procedure in Williamson, I recall that everything was added at once in their procedure. However, experience reveals that unless the NaOH is fresh, the reaction can easily fail. In that case, adding additional NaOH(s) will start the reaction again.

Because the reaction only requires a catalytic amount of base as base is regenerated, I think the success of this reaction is related to rates. If small amounts of concentrated base were used, then product formation would dilute the base and slow the reaction. Addition of base could increase the concentration and increase the reaction rate.

[davink67]

Thanks orgopete, at last someone who tried to understand my question.