Klute - 21-7-2009 at 07:52
This acyl chloride was prepared from the acid and thionyl chloride. This is a very genral procedure, applyable to manya cids, so I though a
experimental would be usefull here.
All reagents used are commercial grade. Thionyl chloride was distilled before use.
In a oven-dried 100mL 2-neck RBF equipped with a stir bar, a condenser and a CaSO4 guard, are charged 18.20mL SOCl2 (250mmol).
18.00mL (200mmol) of (+-)-2-bromopropionic acid was added dropwise at room temperature over 30-45min, with no apparent reaction (no gas evolution).
The flask is slowly heated to a gentle reflux (80°C oil bath), and slow HCl evolution starts. The mixture is refluxed until no more gas is evolved,
ei 3H. The bubbling changes apparence, hard to describ, but first it evident gas is evolved, then it boils like any other liquid.
Exces thionyl chloride is removed under vacuum, and the residu is left under vacuum for one hour to remove the last traces of SOCl2. The crude product
weighs 22.60g (131.8mmol) 65,90%
The crude product is used as is for the formation of an amide with aniline. If anyone is interested in this reaction I can post the details.
[Edited on 21-7-2009 by Klute]
grind - 28-7-2009 at 04:46
Interesting! Good work!
But is there a loss of product during the distillation of the SOCl2 or during the 1h vacuum treatment? The acid chloride is moderately volatile...
Have you ever tried to distill the product in vacuum instead of removing traces of SOCl2 with this 1h vacuum treatment? I think you can increase the
yield if you distill the product directly in a weak vaccum...
Klute - 28-7-2009 at 08:41
Yes, there is some losses di to the volatility of the acyl chloride, didstilling it would have offered better yields and a cleaner product that is
certain... But it is a high bp if I recall correctly.