Sciencemadness Discussion Board

Butanone (MEK) to butyric acid

Random - 17-10-2010 at 04:16

Is there a way to make butyric acid from 2-butanone(mek)?

spong - 17-10-2010 at 04:40

I doubt it would be very easy, if it had been butyraldehyde the story would be different but sadly it would be difficult to make it from MEK. You could make propionic acid pretty easily via the haloform reaction (plus some CHCl3 which is also handy) which could make some nice esters. If 2-pentanone were easy to obtain you could make butyric by the same method.
I've tried the potato fermentation you posted about a while back with a few modifications, so far it stinks but not so much of butyric acid, it just smells... bad. Hopefully some will be produced eventually, it's only been three weeks.

Random - 17-10-2010 at 04:56

Quote: Originally posted by spong  
I doubt it would be very easy, if it had been butyraldehyde the story would be different but sadly it would be difficult to make it from MEK. You could make propionic acid pretty easily via the haloform reaction (plus some CHCl3 which is also handy) which could make some nice esters. If 2-pentanone were easy to obtain you could make butyric by the same method.
I've tried the potato fermentation you posted about a while back with a few modifications, so far it stinks but not so much of butyric acid, it just smells... bad. Hopefully some will be produced eventually, it's only been three weeks.


I took the fermentation product after few weeks of fermentation and I added 1/3 of the whole volume ca(oh)2. Butyric acid smell disappeared and I noticed the smell of ammonia. After that I added so much HCl (19%) to dissolve all ca(oh)2 and calcium butanoate produced. I left this solution for 1 day. Next day there was yellow-green solution and on the corners of the jam jar was something white like when you dissolve soap in the water (I can't explain it completely.) The jar now smells a little bit of butyric acid.


I could try the haloform reaction of MEK, but am I safe if I use MEK mixed with some isopropyl alcohol and CaCl2? There is also some methoxyisopropanol. Propionic acid sounds interesting too. What's the acid produced by acetone in haloform reaction?

spong - 17-10-2010 at 06:11

Ohh that's good news, at least you got the scent of it compared to mine which smells like a mix of all sorts of fatty acids. Did you try extracting it or making any esters?
Isopropyl and acetone will both give you acetic acid, the isopropyl first being oxidized to acetone by the hypochlorite. Did you mean Ca(OCl)2 or is there CaCl2 in your MEK/acetone/IPA? CaCl2 will not affect the reaction, commercial hypochlorite will have significant amounts in it already.
Have a look at the mechanism of the haloform reaction http://en.wikipedia.org/wiki/Haloform_reaction the first carbon pretty much gets chlorinated and then an OH- comes and breaks the chlorinated carbon off forming the carboxylic acid and then the CCl3- picks up a H+ from the solution and forms chloroform.
I tried the reaction once but didn't isolate the propionic acid properly, I acidified the mix after I'd distilled the CHCl3 (avoiding the clouds of chlorine) and expected it to rise to the top as an oily layer but a solvent is apparently needed to get it out of the aqueous phase.

Random - 17-10-2010 at 06:53

Well, It smells like a ginkgo fruit, but at the same time there are some more bad smells. I am not sure how I could isolate it, it should separate as an oily layer with CaCl2, but there is only that white stuff around the borders of jar. Maybe that is butyric acid, I should try to take it from the other stuff.
When I think about it, I could squeeze juice from ginkgo fruits and mix them with Ca(OH)2 and then mix that with HCl. Maybe it would be even better yield than from that fermentation.

Thanks for explaining the reaction, I want to try it, but I am scared because of chloroform. It's not that much chloroform, but it's phosgene that could be formed from it. Maybe you should try salting the propionic acid out with CaCl2?

not_important - 17-10-2010 at 10:48

Given the easy miscibility of both propionic and butyric acids with water, the best way of isolating is to keep/convert to a salt (calcium, sodium) and evaporate the solution to get rid of the large amounts of water (and CHCl3 if from haloform reaction). Then treat the salts with strong mineral acid (con. HCl, 50% H2SO4). If you accept some loses, separate the salt+water layer from the organic, then first distill and then fractionate the organic layer to isolate the acid.

spong - 17-10-2010 at 17:33

I wouldn't worry too much about chloroform/phosgene, a tiny bit of ethanol could be added to stabilize it or you could just leave it in the open for a few hours and let it evaporate (it smells so nice!)
If you wanted to avoid CHCl3 entirely you could perhaps try oxidizing MEK with KMnO4, that should hopefully give propionic acid and formic acid.
To separate the acid from water I'd just extract it with something like ether, that, as well as the salting out should separate it nicely and the ether could then be distilled off. You could probably even use the chloroform you made in the haloform reaction if you can't find ether :P