kt5000
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Ethyl acetate synthesis from ethanol and dilute acetic acid
I've been wanting to get some ethyl acetate to tinker with caffeine extraction. It would be fun to make the ethyl acetate myself..
The Wikipedia page says the following reaction proceeds to 65% yield at room temperature:
CH3CH2OH + CH3COOH --> CH3COOCH2CH3 + H2O
That H2O on the product side is screaming at me.. I can distill ~96% ethanol, but my best source of acetic acid is 5% vinegar. With that
much water in the reactants, I expect nearly zero product formation.
To make that work, I need to remove water from the otc vinegar. I swore I read somewhere that acetic acid forms an azeotrope with water around 5%,
but Wikipedia disagrees. It says there is no azeotrope and the BP of pure acetic acid is 118.1 C. If that's the case, can't I fractionally distill
the vinegar to remove most of the water?
To remove the rest of the water, could I use something like CaCl2 or anyhydrous MgSO4, filter, and distill to remove any
dissolved solid?
Once the reactant solutions are reasonably water-free, I'm thinking of refluxing around maybe 70-80 C in a boiling flask with some dessicant in the
bottom to absorb water as it's produced. The reaction looks slightly exothermic (deltaHrxn = -4.7 kJ/mol) so I'd sacrifice a small amount
of yield for speed. If I add a slight excess of acetic acid and remove most of the water, the product flask should contain mostly ethyl acetate with
a small amount of acetic acid, which could be separated by fractional distillation.
Does that sound feasible?
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Daffodile
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http://www.sciencemadness.org/talk/viewthread.php?tid=8507
Check this stuff out dude. Some people have already talked a bit bout it. Cheers
[Edited on 8-3-2016 by Daffodile]
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kt5000
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Thanks and my apologies, I didn't mean to restart the 'concentrating acetic acid' threads.  Assuming the glacial acetic acid fairy stops by my house, does the rest of the process make sense?
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Pharmacophore
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To the best of my knowledge you could react sodium bicarbonate with vinegar to get sodium acetate. Then boil that down till you get crystals which is
the hydrated form. Then cook in the oven to drive off water. Then you could react it with a strong acid to get pure acetic acid then distill it off.
Sorry if that was a bit vague, or if you already answered your question. Other than that, the reaction should be a Fischer esterification by the looks
of it. It seems you forgot you need sulfuric acid as a catalyst (given you're slightly concerned about speed I don't want you waiting for all
eternity), which will slightly complicate things, once you've reacted everything, you could probably add some cold water (not too fast) and then put
it in a sep funnel. After that do some bicarbonate washings, distill, dry, and you should be good. These are all a bit vague procedures so if you have
questions feel free to ask, and most of this should be on the web.
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Daffodile
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The combined Acetic Acid and Ethanol should be mixed with a few drops of Sulfuric Acid before reflux/ distilling, as it shall act as a catalyst.
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Sniffity
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Hey,
The reaction you plan on doing is what's called a Fischer Esterification.
There's an equilibrium involved, as you mention. Even upon drying the reagents, that equilibrium is still annoying. The best way to work around this
is as follows:
First: Use a large excess of alcohol, shifting equilibrium to the right. Don't use an excess of acid. Makes work up annoying as hell.
Second: Uae a reflux condenser, to shift equilibrium to the right by adding heat. Make sure it boils.
Third: Use a catalyst. Sulfuric acid. Few mLs. Careful not to burn products.
Fourth: Use a Dean-Stark apparatus to remove water from the reaction mix; don't use a desiccant as this will most likely cake on the bottom of the
flask, making a huge mess.
As for the acetic acid, plenty of threads here on purification of that particular reagent.
This is one of the reactions I've studied in great detail. If you search for posts I've made, you'll probably find one in which I ask a LOT of
questions about this reaction (first time doing it back then) and quite a few people chime in to help. I've been reading more about it since then, if
you need any more help feel free to U2U me or post here again.
Also: do some reading on post reaction work up. It's simple, but you want to know what you're doing.
Hope this helped!
-Sniffity
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ParadoxChem126
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Quote: Originally posted by Sniffity  |
First: Use a large excess of alcohol, shifting equilibrium to the right. Don't use an excess of acid. Makes work up annoying as hell.
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Actually in my experience I found it more difficult to use an excess of alcohol. Ethanol, in this case, has a nearly identical boiling point to ethyl
acetate and is subsequently much more difficult to remove during workup. Even with repeated water washings in a sep funnel, it is difficult to remove
all of the ethanol. On the other hand, if you distill after refluxing, most of the acetic acid will be removed and the rest can be reacted with sodium
carbonate solution.
Have you actually used a Dean-Stark in this particular reaction? I'm not exactly certain how applicable that would be here, considering that most of
the vapor that boils off consists of ethanol and/or ethyl acetate. It seems to me that any water that did manage to collect in the Dean-Stark would
homogenize with the ethanol and be impossible to remove.
@kt5000
Fractionating vinegar is unlikely to yield satisfactory results. Acetic acid has a higher boiling point than water, so all of the water must be
distilled off before the acid. Because the boiling points are only 18 deg C apart, much of your acetic acid will be lost during that distillation. It
would be impractical to distill off liters worth of water at a slow enough rate to sufficiently fractionate the mixture. The distillation would take
an extremely long time and require close attention and control of temperature. It does make more sense to convert all of the acetic acid to sodium
acetate and distill with conc. sulfuric acid, but this process is also extremely labor intensive. I suggest buying glacial acetic acid online, it is
widely available (in most countries) and is fairly inexpensive.
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Sniffity
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@Paradoxchem126 Interesting  . I've never done Ethyl Acetate specifically, I
usually tend to go for larger alcohols and acids. Now that you mention it, yes, alcohol removal might be hard. However, there's still the issue that
ethanol is generally easier to come by than acetic acid, and thus easier to use in excess. Hmm.
In this particular reaction, ethyl acetate, I have not used a Dean Stark. What you mention is certainly a possibility, which does not occur in the
synthesis I usually carry out .
On a side note: Don't you happen to have a YouTube channel? I seem to remember having watched an excellent video on Fischer Esterification by Paradox
Chem. Congratulations on the amazing material if that's you.
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kt5000
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That's why I was leaning towards excess acetic acid. With that small bp difference, I'm not sure how I'd do a workup to remove the ethanol.
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aga
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Distilling from modern nail varnish remover is the cheapest and quickest to obtain ethyl acetate - they swapped out the acetone years ago.
Many many posts on this site about it.
Google anything, just add "site: sciencemadness.org" in front of your normal search and google will bring up pages and pages of actually useful info.
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kt5000
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Hey aga, good to hear from you. I lost many hours last month reading the drunken challenge threads 
So they're using ethyl acetate as the solvent in the non-acetone nail polish remover?? The "100%" acetone nail polish remover is still my go-to
source for cheap acetone.
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aga
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Here (Spain) there is the option - acetone or non-acetone (=ethyl acetate).
Personally i prefer the non-acetone as it doesn't dry out my nails so much 
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ParadoxChem126
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For a while, ethyl acetate was available in the U.S. as "MEK substitute" in some hardware stores. I have not been able to find it recently,
unfortunately.
Non-acetone nail polish remover does, however, remain a possible source for experimenters in the U.S.
@Sniffity
Yeah, that channel is mine. I uploaded that video what seems like many years ago, but I'm not exactly sure it's what I would call "amazing
material"... Thanks nonetheless, though.
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Sniffity
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@ParadoxChem126 Re-watched the video. Truth be told, it was the first video I ever watched on a synthesis, back when I switched from Med School to
chemistry. Yeah, certainly a few improvements could be made here and there  .
Still, being the first video I watched it still brings back warm memories . Glad
to meet its creator!
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S.C. Wack
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| Quote: Originally posted by kt5000 | To remove the rest of the water, could I use something like CaCl2 or anyhydrous MgSO4, filter, and distill to remove any
dissolved solid?
Once the reactant solutions are reasonably water-free, I'm thinking of refluxing around maybe 70-80 C in a boiling flask with some dessicant in the
bottom to absorb water as it's produced. The reaction looks slightly exothermic (deltaHrxn = -4.7 kJ/mol) so I'd sacrifice a small amount
of yield for speed. If I add a slight excess of acetic acid and remove most of the water, the product flask should contain mostly ethyl acetate with
a small amount of acetic acid, which could be separated by fractional distillation.
Does that sound feasible? |
No that sounds crazy. You should try it. The second part probably depends on specifics. IDK what the chances would be if one distilled some
"distilled" vinegar and set a dish of that on a big pile of damprid in a desiccator. Possibly improved slightly.
BTW Norris 3rd ed 1933 (paraphrased) seems relevant to the thread's title at least.
Preparation of Ethyl Acetate in the Presence of Water.
Mix in a 500 ml flask 50 g of ethyl alcohol, 60 g of glacial acetic acid, 150 ml of water and 20 ml of concentrated hydrochloric acid. To ensure even
boiling put in the flask a small piece of porous tile. Place a thermometer in the flask to observe the temperature of the vapor, and connect it with a
water-cooled condenser. Distil not faster than 1 drop per second.
Transfer the distillate to a separatory funnel and shake it with 50 ml of a solution of sodium chloride prepared by dissolving 60 g of salt in 200 ml
of water. Draw off the salt solution and repeat the washing three times. At the end of the fourth treatment leave about 5 ml of the salt solution in
the funnel, and add about 0.5 g sodium bicarbonate. Put the stopper in the funnel, invert it, open the stop-cock, and shake cautiously. Enough of the
bicarbonate should be used to neutralize the small amount of acid left after the first washings. When no more carbon dioxide is evolved draw off the
aqueous solution and run the ester into a distilling flask, and add about 15 g of calcium chloride. Let the product stand for at least 2 hours and
distil from a water-bath.
The yield is about 50 per cent of the theoretical.
Note - The preparation of ethyl acetate in the presence of water is introduced to illustrate an important procedure that is used in making certain
organic compounds, namely, the carrying out of a reaction under such couditions that one of the products is removed from thc system as the result of
its volatility. In preparing ethyl acetate in the presence of water, advantage is taken of the fact that when the ester formed is heated in the
presence of ethyl alcohol, acetic acid, and water the product having the lowest boiling-point and consequently distilling first is a constant-boiling
mixture which distils at 70.3° at 760 mm. pressure.
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kt5000
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Thanks for the citation. I'll look up the book.
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Sniffity
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50 percent of the theoretical yield is way too low for this reaction. The book quotes above proposes to catalyse this reaction by the use of
hydrochloric acid. You'll get better results by using concentrated sulfuric acid or p-toluenesulfonic acid. With HCl you'll add water which will mess
with the equilibrium shifting it to the right. Also: the amounts of acid and alcohol proposed by the quoted book will not take advantage of using one
reagent in a large excess.
I'd look for another source. Vogel's maybe?
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S.C. Wack
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| Quote: Originally posted by Sniffity | 50 percent of the theoretical yield is way too low for this reaction. The book quotes above proposes to catalyse this reaction by the use of
hydrochloric acid. You'll get better results by using concentrated sulfuric acid or p-toluenesulfonic acid. With HCl you'll add water which will mess
with the equilibrium shifting it to the right. Also: the amounts of acid and alcohol proposed by the quoted book will not take advantage of using one
reagent in a large excess.
I'd look for another source. Vogel's maybe? |
Not sure that a large excess of either (usually)ethanol or acetic acid is particularly desirable...I'd suspect that the HCl is not an accident, and
that (ethyl)sulfuric acid messes with the yield of the ternary azeotrope...50% seems perfectly acceptable for acetic acid with that much water.
In any case if kt5000 does find Norris, it would probably be Google's 1915 1st ed. that has only one of the usual GAA/alcohol/sulfuric variations in
the lab manuals.
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