Hi bees!
My buddy SWIA vac distilled his ketone gotten from said AcAc Grignard twice - and collected some strange fractions..(?)
First, some different clear liquids came over, followed by a nice fraction of yellow oil - so far so good. He then decided to redistill, because the smell of the oil was still somewhat disgusting and not really like phenylacetone at all...
Said done. First some small amount of clear liquid came over below 80°C at 270torr. Then, a small fraction was collected at 150°C (corresponding to ~185°C at 760torr) - probably benzylchloride, SWIA thought - at least it would explain the disgusting smell of the raw product..
Then, nice greenish ketone came over at above ~165°C (just like P2P should), but the amount was only roughly half of the original volume!
Then distillation ceased and SWIA had to crank the heat control up to over 350°C to be able to collect a large fraction between 210° and 230°C - WTF is that???
Appearance of the unknown substance is oily, slightly yellow and the bp should be around 260°C at ambient pressure - maybe 4-benzyl-3-pentene-2-one? Its bp would match, and https://www.thevespiary.org/rhodium/Rhodium/pdf/p2p.acac-grignard.pdf (https://www.thevespiary.org/rhodium/Rhodium/pdf/p2p.acac-grignard.pdf)
states that said ketone is obtained by heating the bis addition product of this reaction at 130°C under vacuum followed by distillation, so maybe...?
This really puzzles me, especially because you guys have spent that much effort in analyzing the product!? (did SWIA use too little HCl for hydrolysis maybe?)
Any ideas about what could've happened?
[EDIT] after some more 24hours in the fridge, the P2P SWIA isolated has still its beautiful colour - while the higher-boiling fraction has become strongly yellow-tinted[/EDIT]
THX A
The Mg and ether shouldn't be the problem, they're both expensive quality grade reagents,...
Have you explicitly ultra-dried your ether? 'Quality grade' from the bottle might not be enough. :)
If you add the benzylchloride too fast, to the magnesium covered in ether, you will get quite an amount of 1,2-diphenylethane. This boils at 284°C, corresponding nicely with your findings. Read the first five lines from this (https://www.thevespiary.org/rhodium/Rhodium/chemistry/phenylacetic.html)
(https://www.thevespiary.org/rhodium/Rhodium/chemistry/phenylacetic.html) document. It describes the problem and solution quite nicely ;)
Regards
Bandil