TheShedChemist
Harmless
Posts: 7
Registered: 4-2-2019
Member Is Offline
|
|
(Needs work) My process for making butanoic acid from butter?
This absolutely stank and it was awful to make, so I am not doing any more experimenting on it. My yield was exceptionally low, about 1 drop while I
was expecting 10-20g of butanoic acid. I think it all evaporated (I forgot about it for about a week) or was not all released. Any brave should could
try to improve this as I do not want to do this ever again (despite my next project using it). Please excuse any mistakes as I only do this as a hobby
and I am not a qualified chemist by any means. Also, the first part is just some notes I made prior to writing the procedure. The procedure might be a
bit ambiguous, but please tell me if you don't understand what I'm on about, after all, they were only intended for myself.
---------------------------------------------------------------------
Butanoic acid is usually fixed in triglycerides until butter goes rancid where bacteria break down the triglyceride to release butanoic acid, but this
can also be done using hydrolysis
One method of hydrolysing the triglyceride is to use a strong alkali, the process used to make soap (saponification). However, this creates the salt
of the carboxylic acid with the cation of the base, such as sodium.
Any acid with a stronger anoion than the carboxylic acid will displace it, forming a free fatty acid. This is exactly what I want from the butter, so
extraction could be achieved this way
The resulting fatty acid (if the chain length is less than 10) will be in an emulsion with water. To get it away from the metal salt with the stronger
anion, I will do a liquid liquid extraction as the free fatty acid is more miscible in nonpolar solvents. (I will have already separated the longer
chain fatty acids by liquid - liquid extraction as fatty acids with a chain length of 10 or above will not mix with water)
--------------------------------------------------------------------------
Procedure instructions attempt 1:
1.Melt the butter and put in a separatory funnel with equal volume warm (30C+) water.
2.Discard the aqueous layer as this contains no triglycerides, only the odours of butter like diacetyl
3.From a 250g packet of unsalted butter, there should be 200g of fat left, the rest was either water or other components of butter
4.Dissolve 26 g of NaOH in 75ml of distilled water
5.Mix the NaOH solution with the molten butterfat and stir until consistent.
6.While still molten, but not hot enough to release hydrogen chloride, Add the appropriate amount of HCl solution (see table)
This steps converts the fatty acid salt into the free fatty acid
Volume (ml)
Conc. (%w/w)
237
10
79
30
65.5
36
64
37
Is everything still melted? If not, melt everything
7.Stir well, without forming an emulsion. This is where the short chain fatty acids (like acetic and butanoic acid) mix with the water (the HCl is
already neutralised), separating them from the longer chain fatty acids like stearic acid and oleic acid.
*should stink like vomit
8.Do a liquid - liquid extraction of the long chain fatty acid (the molecules that are not in water) and the short chain fatty acids which are in the
water. Drain the denser, aqueous layer, this contains salt and short chain fatty acids.
*the longer chain length fatty acids are insoluble in water, so they form a layer that stays on top of the water
Repeat 7 and 8 three times in total, using water on the repetitions.
9.Do a liquid - liquid extraction on the water - fatty acid mixture once with your favourite nonpolar, non - water miscible solvent (preferably with a
bp below 110 degrees celcius), I chose pentane
10. salt out the short chain fatty acids
11. Do a final solvent extraction for good luck
12.Distil the solvent (for recycling only) until left with around 50 ml
13. Evaporate the remaining solvent (this should stink like vomit, so it could be advised to wear a mask as well as working in a well ventilated
area/fume hood)
14. Store the short chain fatty acids with some care as they are corrosive and the butanoic acid in it stinks
—---------------------------------------------------------------------------------------------------------------------
optional
Separate the SCFAs by fractional distillation (see table)
Short chain fatty acid (chain length below 10)
Boiling point
Odour
Ethanoic acid, n = 2
118
Vinegar
Butanoic acid, n = 4
163.5
Vomit
Hexanoic acid, n = 6
205
Cheesy, like barn animals
Octanoic acid, n = 8
237
Rancid-like smell
Good Luck, I hope I helped someone 
[Edited on 13-4-2022 by TheShedChemist]
|
|
|
Jome
Hazard to Others
Posts: 154
Registered: 10-6-2004
Location: Soutwest sweden
Member Is Offline
Mood: desiccated
|
|
Butyuric acid should be 2.5% or so of the fat. This procedure was a classic at my highschool, I remember the entire building stinking and people
wondering what it was.
That said, perhaps one could transesterify butter fat with methanol/ethanol, then fractionally distill the resulting biodiesel, the lower boiling
fraction should have the butyrate, and smell like pineapple rather than vomit.
|
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
