[TEMP255]

Hi, can someone please help me in determining
1. the side reaction that lower yield,
2. how to improve yield in the following multi-step synthesis. Thanks.

Step 1 Aldol Rxn

[10% NaOH, p-anisaldehyde, acetone, EtOH,] Stirred, Mixture cooled in ice bath....vacuum filter prod (washed with distilled H2O, 10% acetic acid, then distilled H2O again), acetone added to mixture-warmed; then methanol was added, flask was stoppered to let crystallize...cooled in ice bath....prod vacuum filtered (washed with cold methanol).

Product formed is Dianisalacetone

Step 2 Michael Addition

Dianisalacetone put in RBF with methanol, dimethylmalonate, 25% sodium methoxide. Mixture was refluxed. Solution let cool to rt, then cooled in ice bath.....product isolated via vacuum filtration.

Step 3 Acetal Formation

Product of Step 2 (dimethyl 2, 6-bis(p-methoxyphenyl)-4-oxocyclonehexane-1,1-dicarboxylate) added to RBF along with ethylene glycol, p-toluenesulfonic acid monohydrate, and toluene. Reaction was distilled. Mixture let to cool to rt, and then 0.25 M NaOH was added to the RBF, water was also added. The mixture was poured into a separatory funnel, (rinsed with diethyl ether)..The lower aqueous layer was drained out....Organic layer moved to E-flask, and thus gently heated on steam bath to reduce volume to 2-3mL...Then methanol was added to soln for recrystallization.....cool in ice bath...vacuum filtrate..

Final Product: Ethylene Ketal.

[Borek]

Please read forum rules.

[gobuckskb9]

I am also doing this lab, and I am looking for a way to improve yield or purity. I found this:
http://www.cerlabs.com/experiments/0534681417.pdf
But it doesn't seem to help very much, it just tells me what I already know.
If anyone actually has an idea about this, I would appreciate it.

[orgopete]

Often these questions are related to the stoichiometry and not the process of doing the reaction or the structure of the product. As indicated, they are not providing any specific information about how to improve the reaction.

[Markov]

Try to figure out where in the sequence you lose your material.
Remember that it is sometimes impossible to get good yields in small-scale crystallizations.
Or have you detected that there is a competing side-reaction or impurity in one of the steps ?
cheers