Rhodium
(Chief Bee)
06-10-02 07:47
No 319296
      P2P oxime in quantitative yield
(Rated as: excellent)
 Bookmark   

Phenyl-2-Propanone oxime
J. Chem. Research (S) 24–25 (2000) (../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
(Rehabilitated)
06-10-02 15:19
No 319399
      just gotta luv them oximes, yup :-) .  Bookmark   

just gotta luv them oximes, yupsmile.
 
 
 
 
    Chromic
(Hive Addict)
06-10-02 20:14
No 319482
      Makes me wonder  Bookmark   

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
(Chief Bee)
06-10-02 21:14
No 319499
      "Optimizing", not "skipping"  Bookmark   

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
(Newbee)
06-11-02 17:56
No 319837
      Wierd  Bookmark   

Iīve had this article since April 2 and I havenīt really read it until I saw your post.tongue