Author Topic: P2P oxime in quantitative yield  (Read 1300 times)

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Rhodium

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P2P oxime in quantitative yield
« on: June 10, 2002, 07:47:00 AM »
Phenyl-2-Propanone oxime

J. Chem. Research (S) 24–25 (2000)

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/oximes.cao-nh2oh-hcl.html)

Phenyl-2-Propanone (1.34g, 10 mmol) and finely powdered calcium oxide (5g, 89 mmol) was placed in a flask and heated in an oil-bath for a few minutes. Then hydroxylamine hydrochloride (2.08g, 30 mmol) was added, and the mixture was stirred with a magnetic stirrer in the presence of air for 1 minute at 130°C. Afterward, the reaction mixture was mixed with ethyl acetate, filtered to remove the calcium oxide, then mixed with water and extracted with ethyl acetate. The pooled organic phases was dried over Na2SO4, filtered and the solvent evaporated in vacuo to give phenyl-2-Propanone oxime (1.49g, 100%) in a syn/anti ratio of 9:1.

Antibody2

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just gotta luv them oximes, yup :-) .
« Reply #1 on: June 10, 2002, 03:19:00 PM »
just gotta luv them oximes, yup :) .

Chromic

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Makes me wonder
« Reply #2 on: June 10, 2002, 08:14:00 PM »
Procedures like this make me wonder if Sonson's procedure really needs 1.5 hours of reflux to complete the conversion.

I also think the drying is unnecessary, I imagine the water would be removed with the ethyl acetate.

Rhodium

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"Optimizing", not "skipping"
« Reply #3 on: June 10, 2002, 09:14:00 PM »
Many "classic" routes have reaction times which can be shortened, it is just that the advertised times are proven to work every time with full yield, if refluxing for say 20-30 min instead of 90, very possibly the yields will be lower than usual in at least 10% of the performed runs. It is up to yourself to decide if your time or the yields which is the most valuable to you.

Same thing with the drying in the procedure above - it CAN probably be skipped, but your product will be more moist than with the drying, and with water present some hydrolysis will always occur - if it is to an extent of 0.1% or 5% we don't know until someone has tested the procedure both ways.

Myself, I always prefer to do things by the book first, and then SLOWLY cut back on steps, reaction times or solvent amounts I believe is excessive. I would hate to lose product (or decrease purity) just because I was lazy, even if the difference was just marginal.

Barium

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Wierd
« Reply #4 on: June 11, 2002, 05:56:00 PM »
I´ve had this article since April 2 and I haven´t really read it until I saw your post. :P