02-09-02 15:19
No 267407
36g L-alanine was added to saturated NaBr solution (91ml). ~45% HBr (135mL) was added to this dropwise with stirring.
This solution was cooled to 0C and NaNO2 (56.3g) was added a little at a time over a period of 1.5hrs. After each addition of NaNO2, some nasty orange gas was evolved with fizzing. The addition should be done so that the mixture does not rise above 5C. This needed a lot more cooling than SWIM had anticipated. She had this stirring in an salt/ice bath in a little fridge with internal temperature (of the fridge) near 0C. SWIM didn't monitor the temp while the addition was proceeding since so much noxious gas was being evolved and her thermometer wouldn't fit in the fridge. When the addition was complete and the fumes slowed enough to bring the flask out of the fridge, the temp was near 20C. She's not sure if it was this way throughout the addition or just toward the end when she was getting impatient and added the NaNO2 a little too fast.
The flask was once again cooled to 0C and stirring continued for an additional hour and then allowed to warm to 20C. A light yellow oil seperated from the mixture on the bottom of the flask. SHe seperated this liquid which amounted to around 26ml. It's density was between 1.6-1.7 (the density of the 2-Br-propionic acid is 1.7).
She chose toluene as her organic and extracted the remaining aq solution with 2, 250ml portions.
Now she's looking at these extracts and a layer has formed on the bottom. Without seperating it, it looks like it might be the product. Apparently 2-Br-propionic acid isn't so soluble in toluene (or at least wet toluene- solvent hasn't been dried yet) DCM will be used next time.
Updates will follow..
Next time SWIM is going to use a huge-ass salt/water bath and an oversized flask fixed with a thermometer. Addition of the NaNO2 will be slowed so that the temperature stays in the desired range..
But.. not too bad to SWIM's first shot. SHe thinks this procedure has some real merit considering how she fucked up on the temperature regulation.
xoxo-Julia
(Hive Bee)
02-09-02 16:13
No 267418
Swim has tried and failed everytime with sodium Borohydred. This os one exothermic motherfucker and if there is any water in the mix it is even worse so if your not already dry everything!!!
Is there some secret to the addition nobody is disclosing to the hive bees.
Thoughts on the addition and open questions about this reaction and speed synths that use NaNO2.
1. Methonal and NANO2 added in a liquid staTE?
2. Methanol or some other solvent in the flask and the reaction mix added to it?
What is the proper way to do this?
Don't look at me I didn't do it!
(Hive Bee)
02-10-02 15:18
No 267709
Are we talking about two different synths here?
DCM dissolves the bromoacid.. (stupid! stupid, STUPID) WHy did SWIM have to go novel and extract the thing with toluene..
What about an a/b extraction with this and then distilling in water?
xoxo