Another try was made, using 0.54 mol BzMgCl and, unfortunately, 30 grams sodium acetylacetonate and 24ml acetylacetone in ether (due to a brain glitch; the actonate salt was prepared in large quantity time ago, and the chemist thought he still had enough, until during the reaction, when he realized there was in fact only 30g left
).
Maybe this accounts for the low yields, too - the bis addition product may have formed in significant quantity, but anyway:
yield from this 0.54 mol run was only 13.4ml phenylacetone! (too disappointed to calculate any yield anymore
) And the hydrolysis as well as the vacuum distillation of crude product was done *very* carefully. And all traces of acid were removed by shaking the ethereal extracts of rxn twice with sat. sodium bicarbonate solution, followed by 2 washes with brine. Ether was stripped using a rotavap, the remainder was distilled under 20torr vacuum and P2P was collected between 108° and 118°C (note that steam temp. fell from >50°C to 24.5°C before it suddenly jumped to >100°C after a long while of heating - all fractions collected before were clear liquids with bp's below 70°C, therefore the ketone should've been distilled very sharply, with good separation from by-products).
The remainder was flooded with 230ml H2O and steam distilled, hoping to reverse said dehydration process somehow, and is still in progress...
Honestly, I don't think the dehydration due to traces of acid being present is the explanation for this wierd, high-boiling side product (which is sadly more the main product
). Maybe something was wrong with this huge batch of acetylacetone*Na. The Mg and ether shouldn't be the problem, they're both expensive quality grade reagents, the AA is tech grade (still very xpensive though
), and - lo and behold - the BzCl used is analytical grade, well branded too
, so the reactands are not the problem I think. The technique should be good enough to reproduce Bandil's results (at least getting the Grignard to start isn't any problem, and separating, washing and distilling organic liquids belongs to the few things SWIA as well as me are pretty familiar/skilled with).
HELP!
Are there any important things to consider (besides dryness of reaction, patience, attention, safety, precise measurement and practice of course
) when doing this reaction?
Is the purity of the acetylacetonate salt essential for success maybe? I suspect that the salt that was used in the several miserable trials maybe contained traces of NaOH and therefore fucked up everything with "in-situ hydrolysis" while adding it? (just my thoughts; I'm a bit lost...
)
Greetz A