Sciencemadness Discussion Board

Butane to Butyric Acid

Detonationology - 7-2-2016 at 21:54

Most lower carboxylic acids (formic, acetic, propionic) and their salts are relatively easy to find as an amateur; however, butyric acid and butyrate salts are quite expensive and inaccessible to most amateurs.

A common method of producing butyric acid is by oxidizing 1-butanol with KMnO4. While KMnO4 is quite accessible, there's yet another road block: 1-Butanol is not very accessible to the amateur.

To the amateur, butane gas a widely available, relatively pure, 4 carbon compound and appears to make a good candidate for this reaction. Most brands are sold and labeled as "refined" and are likely a mixture of butane isomers.

Although a mixture of products would be produced, it seems the only chance of producing 1-butanol from butane would be by halogenation, then hydration.



Several questions arise:

1) Assuming that butane is sold as a mixture n-butane and iso-butane, would the halogenation of such mixture produce the same products as the halogenation of n-butane alone, 1-[X]butane and 2-[X]butane?

2) Can a strong halogenating agent or a diatomic halogen be used to halogenate butane? If so, is the reaction exothermic, and is there a risk for a runaway?

3) Can anything or any action be done to favor 1-[X]butane over 2-[X]butane?

4) Is there a much simpler way of doing this reaction that I am missing? If so, please post your method!

[Edited on 2-8-2016 by Detonationology]

gsd - 7-2-2016 at 22:22

Halogenation of hydrocarbons is a tricky process.
1)Even if you start with pure n-Butane, halogenation with either Cl2 or Br2 will result in cocktail of multiple substituted products.

2) Halogen attack is likely to be on the "middle carbons" rather than the terminal ones.

3) The reaction will be strongly exothermic but risk of run-away can be avoided by limiting the quantity of Halogen.

IMHO it will be easier to source n-Butanol and convert it to butyric acid, or if NBA is completely out of your reach but n-propanol is available then you can convert it to butyric acid via:
n-propanol --> n-propyl chloride --> Grignard -->( CO2) --> Butyric Acid.

gsd

Praxichys - 8-2-2016 at 11:55

- Butane could be free-radical chlorinated in the gas phase using an extreme excess of butane under shortwave UV illumination. This would produce a mixture of mainly 1-chlorobutane with some byproducts of 1,1- and 1,2- di, tri, tetra, penta, and hexachlorobutane. These would be condensed from the exit stream and hydrolyzed in a hot NaOH bubbler to give the corresponding alcohols. n-butanol could be fractionally distilled from the mix. Bromine could also be used in this process. Note that standard borosilicate glass is nearly opaque to these wavelengths. Quartzware is recommended, or direct exposure of the reaction to the quartz glass of the lamp.

- Butter from cow's milk contains triglycerides, of which 3-4% are butyrates. You could boil butter in NaOH solution and run an aqueous extraction to get the sodium salts of the fatty acids in the butter, including sodium butyrate. Re-acidifying will free the acids where they could be fractionally distilled to isolate butyric acid. I believe Chevreul himself did this.

- If you can get your hands on clostridium acetobutylicum (I saw live cultures available online), you can ferment starches into a mixture of acetone, n-butanol, and ethanol in approximately a 3:6:1 ratio. See the ABE process for details. Louis Pasteur did it in 1861 so it probably isn't out of reach to the amateur. There is some discussion about this here.

- You could pick up pure GABA (γ-aminobutyric acid) powder online/at a vitamin store and treat it with nitrous acid to get the diazonium compound, then heat to decompose it to butyric acid. All you need is a nitrite salt.

- Many automotive brake fluids contain n-butyl ethers. (Try DOT 3) These ethers can be cleaved by a strong acid (maybe HBr in-situ by using NaBr and H2SO4) to form the corresponding alcohol and alkyl halide. This mix of halogenated alkanes and alcohols could be boiled with a NaOH solution to revert them back to alcohols and recover NaBr. The mix of alcohols would then be fractionally distilled to get n-butanol, which is then oxidized to butyric acid. This particular stuff after HBr/NaOH treatment should yield only ethylene glycol and n-butanol since the methyl and ethyl bromides/alcohols would likely volatilize in the acid treatment step. (And could be collected separately)

- EXPO whiteboard cleaner is mostly propylene glycol n-butyl ether. The same process as above could give high yields of n-butanol.

- Amyl alcohol (n-pentanol) could be oxidized to valeric acid with KMnO4. You could react an ester of valeric acid with ammonia to form valeramide, which can undergo a Hofmann rearrangement to 1-aminobutane. A Sandmeyer reaction on the amine would yield the 1° n-butyl halide, which could be hydrolyzed by NaOH to n-butanol.

- My local vitamin shop has capsules with magnesium, calcium, and sodium butyrate. Just ask for "butyrate."

- You could buy butyl acetate (or a similar ester) on eBay and hydrolyze the ester with NaOH to get n-butanol and sodium acetate.

There are a few eBay listings for both n-butanol and butyric acid. Compared to the equipment cost to make butyric acid, simply buying it would be much cheaper if you're looking for a usable amount with guaranteed purity.

[Edited on 9-2-2016 by Praxichys]

Detonationology - 8-2-2016 at 13:09

Wow, I need to do my homework next time! I bet the butter method would smell absolutely great!

The GABA method is of interest due to the relative accessibility and low cost of reagents; however, the mechanism closely resembles cookery. If my math is right, 1lb of GABA (~$15) would yield only about 410mL of butyric acid :(

My goal, is to produce butyric acid as cheaply, easily, and efficiently as possible. It is unfortunate that the butyrate salts are so expensive, or it would be the most viable option for an amateur. At $35 a liter, n-butanol is still quite expensive, but seems to be the most practical, cost efficient way of making butyric acid.



[Edited on 2-8-2016 by Detonationology]

gdflp - 8-2-2016 at 13:38

Quote: Originally posted by Praxichys  
- Butane could be free-radical chlorinated in the gas phase using an extreme excess of butane under shortwave UV illumination. This would produce a mixture of mainly 1-chlorobutane with some byproducts of 1,1- and 1,2- di, tri, tetra, penta, and hexachlorobutane. These would be condensed from the exit stream and hydrolyzed in a hot NaOH bubbler to give the corresponding alcohols. n-butanol could be fractionally distilled from the mix. Bromine could also be used in this process.

I just want to point out that bromine could not be used in place of chlorine for this particular reaction. Free radical bromination is quite a selective reaction in simple hydrocarbons, with the reaction almost exclusively resulting in the halogenation of the most substituted carbon. In this case, nearly no 1-bromobutane will be produced, instead it will be a mixture of 2-bromobutane and polyhalogenated compounds.

chemrox - 8-2-2016 at 16:20

Really disgusting stuff. I spilled some when I ran the UG stockroom and hitchhiked home... some comments were made...;^)

blogfast25 - 8-2-2016 at 16:26

Quote: Originally posted by chemrox  
Really disgusting stuff. I spilled some when I ran the UG stockroom and hitchhiked home... some comments were made...;^)


Opinion seems to differ a bit on that (I've never smelled it other than in rancid butter). It stinks but how people perceive that varies a lot, from what I've read...

[Edited on 9-2-2016 by blogfast25]

Detonationology - 8-2-2016 at 18:32

I believe that the smell of flatulence and vomit combined best describes butt-yric acid. It's got kind of a sour tinge that stick around in your nose for a while.

[Edited on 2-9-2016 by Detonationology]

blogfast25 - 8-2-2016 at 19:10

Quote: Originally posted by Detonationology  
I believe that the smell of flatulence and vomit combined best describes butt-yric acid.


Nice! I'll look out for that next time that Doner kebab disagrees with me. :(

Ozone - 8-2-2016 at 20:36

You can shunt the nutrient requirements for C. acetobutylicum and stop at the acidogenesis stage, butyric acid, that is. Yields would be improved by running an extractive fermentation.

Alternatively, there are many other strains you could look into that are BSL 1 and selectively produce butyric acid (most are anaerobic, so you have to work with that).

Butyric acid smells like puke when dilute, like cheesy-puke when more concentrated. It hangs with you forever, and once you've smelled it, you will smell minute traces of it in foods, etc. Ugh.

O3

Praxichys - 9-2-2016 at 08:06

Quote: Originally posted by Ozone  
Butyric acid smells like puke when dilute, like cheesy-puke when more concentrated. It hangs with you forever, and once you've smelled it, you will smell minute traces of it in foods, etc. Ugh.

I was searching for words, and you found them. Cheesy puke. The girlfriend smells buttered popcorn, and I can get on board with that at low concentrations.

Oddly enough, this is the same smell I perceive when I smell melted cheese. I can't stand the stuff! I love all sorts of cheeses, but for some reason the second it gets warmed up and gooey, it smells like "cheesy puke" to me and I have a hard time swallowing it. I literally don't eat anything hot with cheese on it, and I lose my appetite when the girlfriend broils up some nachos in the oven and fills the house with that puke-tastic stench. I guess that makes up for the time I suggested she smell some pyridine. (Ha!)
Quote: Originally posted by gdflp  
I just want to point out that bromine could not be used in place of chlorine for this particular reaction.

I did not know that! Thank you. For anyone who is interested in learning:
http://www.masterorganicchemistry.com/2013/10/31/selectivity...

blogfast25 - 9-2-2016 at 08:28

Quote: Originally posted by Praxichys  

I did not know that! Thank you. For anyone who is interested in learning:
http://www.masterorganicchemistry.com/2013/10/31/selectivity...


Nice link!