Copenhagen - 17-11-2010 at 13:32
I found a method for drying an allyl alcohol/water azeotrope by adding carbon tetrachloride and distilling out a lower boiling azeotrope that carbon
tetrachloride forms with water leaving more concentrated allyl alcohol behind. This method comes from organic synthesis which I have included as an
attachment.
Yet in an allyl alcohol safety data sheet it says that allyl alcohol should not be mixed with carbon tetrachloride as it forms explosive products. Am
I correct in deducing that this warning applies to 99% allyl alcohol but not 70% allyl alcohol? Am I correct that as long as there is as much water as
carbon tetrachloride that it is safe to add the carbon tetrachoride to an allyl alcohol/water mixture and distill at atmospheric pressure?
Attachment: ALLYL ALCOHOL from Organic Synthesis.pdf (80kB)
This file has been downloaded 642 times
Attachment: Allyl Alcohol Safety.pdf (591kB)
This file has been downloaded 455 times
smuv - 17-11-2010 at 16:12
You should be able to 'salt out' the water from the 70% product to produce something closer to +95% allyl alcohol.
Do you really need absolutely anhydrous allyl alcohol?
Copenhagen - 17-11-2010 at 16:58
I've tried salting it out and the density was equivalent to about 90% allyl alcohol. I don't need it completely anhydrous but salting out seemed to
waste some of the allyl alcohol as well as some of my potassium carbonate. I ended up with 82 mL at 90% starting from 600 mL raw product. It is nice
to have options, salting and separating, salting and separating is tedious and not quantitative for this procedure. If it's the only way I don't mind
but it's always good to have options in my opinion especially since my lack of manual dexterity favors the distillation technique over the sep funnel
or decanting a flask.
mr.crow - 17-11-2010 at 18:03
My guess is they didn't care about safety in the 40s when they wrote that article for orgsyn. It is CCl4 after all.
If it is cold and you do it quickly then maybe not enough will form to be a problem.
Here is a related question: Can allyl alcohol be made from 1,2-propanediol by heating with phosphoric acid? I think it will make propionaldehyde
instead.
Copenhagen - 17-11-2010 at 21:15
It is from the 1940s - good point. I have not seen such a synthesis for allyl alcohol starting with propanediol but that doesn't mean there isn't
one. I've only seen the glycerol and propylene oxide and allyl chloride hydrolysis methods. I do know that 1,5-butanediol can be converted to
tetrahydrofuran via vapor phase acid-catalyzed dehydration. I think that is cool.
chemrox - 17-11-2010 at 21:51
I wonder if refluxing with toluene using sieves or a dean-stark would collect enough water?
Copenhagen - 17-11-2010 at 21:58
Hmm. That sounds very interesting. I have access to a dean-stark apparatus too.