[clw105]

Hey everyone,

A quick question about the Biginelli Reactions...

My reagents are the general ones- benzaldehyde, followed by the addition of ethyl acetoacetate (to protonate the carbonyl oxygen), and subsequently, the addition of urea.
My question is ..why add urea last?  I figure there must be some ridiculous side reaction occurring between urea and benzaldehyde, or the acid, but I can't figure it out for the life of me.

My other question is...I used ethanol as the solvent, after the addition of these three compounds.  I then added 1 drop of HCl...why does HCl need to be added last?  Looking at the mechanism, my assumption was that HCl would protonate urea, thus decreasing its availability for reaction...but my TA said this was wrong to some degree...or not the complete answer anyways.

Thanks in advance!