05-12-03 18:43
No 432879
I'm trying to isomerise allylbenzene to propenyl using this proceedure"
"Isomerisation of 2 to 7. (Safrole to Isosafrole). To 80.0g (0.49mmol) of 2(safrole) was added 100mL of a 3N solution Of Potassium hydroxide in n-butyl alcohol and the reaction mixture was stirred at room tempreture for 3 h. The mixture was poured into a solution of 12mL concentrated HCl, and 52mL of ice water. After neutralization with additional concentrated HCl, the organic layer was extracted with three 35-mL portions of ethyl acetate. After usual workup, A white oily residue was obtained and distilled to furnish 78.4g (96-98%) of the styrene derivative 7(isosafrole) as a colourless oil. J.Pharm.Sci Vol.81, No.12 1220-1221 1992."
I'm having difficulty making sense of this particular step;
"the organic layer was extracted with three 35-mL portions of ethyl acetate."
How to you extract oil from BuOH when ethyl acetate is soluable in BuOH? Am I missing something very fundmental here! By the way I refluxed, not room temp for 3 hours.
Thanks,
FF.
Be joyful, though you've concided the facts
(Newbee)
05-12-03 18:55
No 432883
HCl is an aqueous soln.. youve also included ice. extraction with ethyl acetate will allow you to seperate out the water... try it... you should get two layers ...
(Hive Addict)
05-12-03 19:01
No 432884
I dont get it why bees make it more complicated than it needs to be. If you simply want isosafrole, the isomerizing safrole with dry KOH with good stirring @150C @ 1ATM for 16hours will bee so much simplier and the yields around 95%.
(Hive Bee)
05-12-03 19:02
No 432885
But I already have two layers, the neutralised water and the oil/Butanol layer. Are you saying that the acetate is used to extract more water? Sorry I don't get it.
Hidden, I'm making propenyl not isosafrole. I know the proceedure is the same, but I had problems removing water from 3-Phenyl-1-Propene without loosing a lot of the allyl and when I did reflux the thing, with 2% KOH, 23hrs, I got no tempreture rise and no conversion. Also, I've tried drying KOH in the oven (electric) at all sorts of temps, beats me how you guys do it. I always end up with a pool of mush.
Regards,
FF.
(Chief Bee)
05-13-03 14:54
No 433010
"the organic layer was extracted with three 35-mL portions of ethyl acetate."
They surely mean that the organic compounds were extracted from the final two-phase solution with ethyl acetate. Not separating the organic layer before extracting the aqueous phase with EtOAc may have some merit (or maybe not) but it certainly won't harm anything by doing it.
(Hive Bee)
05-13-03 19:34
No 433060
What I actually did before posting was separate the water from the organic phase then add the acetate, disolved nicely, stared at it for a while then added back the water and mixed. Didn't seem amy different to me so deceided to separate again and fractionally distil the lot.
First came the acetate azeotrope, acetate, BuOH azeotrope, BuOH, then Allylbenze! No isomerisation. I'll go back to trying Allyl with KOH only, and remove the water better with a column. Can't believe this is so much trouble.
Regards,
FF
Be joyful, though you've concided the facts!