Sciencemadness Discussion Board

Alkyl Phenyl Ketones Synthesis through Dry Distillation

shr3k - 26-4-2015 at 13:47

Hi guys,

Spending a lot of time researching lately and learning but something has me confused.

I have been reading the Benzene production threads on here and am amazed at the work Organikum/Ordenblitz and others did. It as made benzene one of the first experiments I wish to do once I am set up safely and properly.

However the Aryl Ketone Synthesis through dry distillation has been something of interest. Similar to the benzene but Carboxylic Salts are used. I have read posts stating Calcium Salts were used with low yield, but noticed that Organikum had success with Iron Salts.

Further reading led me to a thread on here but the last 2 posts are somewhat confusing.

Manimal posted:


See here: instead of risking oxidative degradation by recovering iron acetate from solution, it can be made in situ from ferrous sulfate and sodium carboxylate; this would form ferrous carboxylate and sodium sulfate. The NaSO4 would stick around, but may act as a bulking agent and not interfere with the decarboxylation.

Thread: Alkyl Phenyl Ketone

As above it seams that Manimal has suggested (with a See here but no link) that Iron Sulfate would react in situ with the Sodium Carboxylate to form the iron salts prior to the Decarboxylation.

If this is the case Sodium Salts might be easier to synthesize or buy than the Iron Salts, and Iron Sulfate is good to go.

However, in the same thread above bbartlog seams to confuse carboxylate with carbonate and the thread goes into a bit of a mess leaving me with spending countless hours researching Manimals post with not much success.

I am struggling to understand why Sodium Carboxylate (Let's use Sodium Benzoate for example) would react with Iron Sulfatte prior to decarboxylation to form iron salts.

Also is he referring to Ferrous Sulphate or Ferric Sulphate as Ferround Sulphate or Iron II Sulphate is pretty common and would make the above synthesis more desirable.


shr3k - 27-4-2015 at 14:33

Update time:

After looking over the benzene threads I decided on a small metal paint can to test the above theory. The paint can was cleaned, wire brushed, heated and cleaned several times until clean metal was visible. The lid was then drilled to allow a small copper connection to be sealed, this was sealed with PTFE thread tape on the threads and brazed around the paint can lid connection.

The vessel was then filled with roughly 50ml water and heated using a large camp stove heater. A steady column of steam came out of the copper tube. The vessel was dried and set up for distillation with the copper tube fed into a condenser and finally to a receiving flask.

Sodium Propionate 43.030g (0.5 mol) was mixed with Sodium Benzoate 72.05g (0.5 mol) and Ferrous Sulfate Pentahydrate 241.984g (1 mol)

All 3 were dry powders and sieved to remove any lumps. When thoroughly mixed a pinkish hue was noticed which seamed to darken while mixing.

50g of the above mixture was placed into the vessel prepared above, the vessel was sealed and the water flow was turned on. Heat was applied to the vessel from the camp stove and the vessel quickly became heated to a point where it glowed orange.

Liquid was seen to come across quickly, first a milky free flowing liquid with no obvious smell, followed by an oily orange liquid which gathered on top of the water until enough have collected and sank.

Several more runs were completed with the above set up to yield enough liquid to work with.

Several key points:

1) During the distillation some small white shards of ice looking precipitate formed around the entrance to the condenser flask, unsure on compound.
2) The smell was a fruity/spicy odor reminiscent of childhood memories of Small household plants with furry green leaves and colorful flowers, Unsure on name.
3) The smoke produced during distillation only seamed to occur on higher heats, lowering the temp slightly kept distillate flowing but produced no smoke.

The product is now in a flask ready to be split out. The orange liquid is oily and gloopy not seaming to form a precise layer, so using the seperatory funnel may not work, I will try this first, hoping to be able to wash the orange liquid with water a few times, then distill it to yield the final product, believed to be Propiophenone.

Watch this space, I will try and get pictures etc later today, was just trying to see if the idea worked.


shr3k - 27-4-2015 at 14:56

Poor camera quality. 160ml of liquid roughly, maybe 40 of that is the orange liquid.

As the temperature of the room has now dropped from 22 degrees celcius earlier to 12 degrees celcius now, it appears that the orange liquid has started to crystalize, indicating even more that it could possibly be Propiophenone.

DSC_0189.JPG - 1.2MBDSC_0190.JPG - 971kB

Chemosynthesis - 27-4-2015 at 15:33

Very nice. I would have expected some biphenyl impurities and am interested in seeing how this progresses.

zed - 27-4-2015 at 18:54

These reactions usually are run with an over-abundance of the cheapest reagent.

When phenylacetic acid is employed as one reagent, and acetic acid as the other; the acetic acid might be employed at high excess. This tends to maximize the yield of phenylacetone, minimize the yield of biphenyls, and it produces a lot of acetone.

You probably have a mixture of ketones as your product.

shr3k - 28-4-2015 at 13:00

I've been advised by some others that an increase of Sodium Benzoate could improve yields.

I've been busy today but will analyse this evening and fraction off the different products.

Pumukli - 29-4-2015 at 04:05

Hello shr3k,

Aren't those little "shards" mean sublimed benzoic acid? I think melted ferrous sulfate forms an acidic melt and may provide path for benzoic acid. (Propionic as well, but it does not form crystals at that temp.)

What a coincidence: yesterday I was reading an old org. chem book on the website. In that book there was an acetophenone synthesis based on the pyrolysis of calcium salts of benzoic and acetic acids. You can check that recipe here:

A class-book of organic chemistry, by J.B. Cohen ... v. 2. Cohen, Julius B. (Julius Berend), 1859-1935.

The synthesis description is on page 8.

(The link may or may not work, I copied it from my browser.)

shr3k - 1-5-2015 at 13:37

Quote: Originally posted by Pumukli  
Hello shr3k,

Aren't those little "shards" mean sublimed benzoic acid? I think melted ferrous sulfate forms an acidic melt and may provide path for benzoic acid. (Propionic as well, but it does not form crystals at that temp.)

What a coincidence: yesterday I was reading an old org. chem book on the website. In that book there was an acetophenone synthesis based on the pyrolysis of calcium salts of benzoic and acetic acids. You can check that recipe here:

A class-book of organic chemistry, by J.B. Cohen ... v. 2. Cohen, Julius B. (Julius Berend), 1859-1935.

The synthesis description is on page 8.

(The link may or may not work, I copied it from my browser.)

I'mm still trying to work out what was produced from the above. There seams to be very little Propiophenone.

I am not sure whether the Iron II Salts produced were sufficient as Organikum mentioned Ferric Chloride to produce the iron salts, which would be Iron III?

Still working on the process and which route works. Calcium salts for Acetophenone worked brilliantly, guessing the temperatures were better, but low yield 7% of Propiophenone from Calcium Salts of Benzoic and Propionic Acids.

Organikum mentioned Iron salts being the best for Propiophenone.

Still lots of research to do!

Pumukli - 2-5-2015 at 08:35

Ferric ions are Fe(3+) ions, yes. Ferric chloride can be bought OTC because the hobbists are using it (at least they used to use it) for printed circuit board etching. It is the orange colored hydrated form, not the black anhidrous FeCl3, but it should suffice. Ferric sulphate may be bought at a pool's supply shop as far as I know. It is used as a flocculant if memory serves well. :-)

One more thing: have you noticed that in the acetophenone recipe they started the heating from the upper parts and worked downward? It may not make a big difference but as I remember from the benzoic acid -> benzene thread the heating and the heat transfer inside the "reactor" is not a trivial one!

[Edited on 2-5-2015 by Pumukli]

zed - 10-5-2015 at 13:53

Actually, this synthesis is often accomplished either by pyrolysing lead salts, or via reacting the free acids, over a catalyst, in a tube furnace. Vogel provides details of synthesis via tube furnace. And, I'm pretty sure the archives will provide details on pyrolysing the lead salts of carboxylic acids.

Many references will probably refer to the synthesis of Benzyl Methyl Ketone (P2P). Since we are talking about producing Propiophenone, yields might differ wildly. Could also be a significant portion of benzene in the product. Or...........

As for increasing Benzoic acid; do as you will. But, it is most likely that Propiophenone yield will be increased by increasing Propionic acid. Hopefully, this insures that the most prevalent products will be 3-Pentanone and Propiophenone.

byko3y - 10-5-2015 at 15:41

I'm sure there is some good conditions that could give nice high yield of alkyl phenyl ketone, but it is just not discovered yet :/
"Decarboxylation Studies. II. Preparation of Alkyl Phenyl Ketones"
J. Org. Chem., 1963, 28 (3), pp 879–881
DOI: 10.1021/jo01038a521
Table II
Yields of Propiophenone by Pyrolysis of Iron Salt Varying Ratios of Benzoic Acid and Propanoic Acid
Molar Ratio Yield %, propiophenone Benzoic acid Propanoic acid isolated 4 1 72 2 1 60 1 1 50 1 2 55 1 4 59

The data is logical, because propanoic acid readily reacts with itself, while benzoic acid decarboxylates to benzene sluggishly (at least at the temperature authors used).
Although this one was solvent-free, you might want to try diphenyl ether as a solvent (many others lead to even lower yields).

Dennis A - 22-5-2018 at 12:05

Was this procedure ever optimized ? if so i would love to hear more and are iron salts still the best ?

I did however have a chance to watch chemplay3rs video on the dry distillation calcium benzoate/propionate a pleasure to watch but his yields were very low even before purification so to obtain an amount worth the effort one would have to scale up a " considerable " amount just to compensate for the yield let alone the purification

The friedel crafts acylation or dry distillation to obtain structurally similar ketones is a topic of interest for me as for acylations the need to avoid acyl halides and AlCl3 etc is essential i have read this can be achieved by H3PO4/P2O5 and p-TsOH/Graphite some literature examples on the net the odd patent but nothing of personal experience and discussion etc

Does anybody have any experimental advice ?

p-TsOH is very easy to synthesize and purify and as for graphite OTC , However i have not doubt other metals will work or be better i know ZnO has been used to catalyze acylations but that was using halides not carboxylic acids



JJay - 22-5-2018 at 12:54

I have not personally tried making ketones by pyrolyzing iron salts. I have tried it with calcium salts. The yields were terrible (25-30%). The temperatures required are pretty high, but I think temperature control is essential to avoid decomposing the product. Vacuum distilling a mixture of calcium benzoate and calcium acetate (1:3 molar ratio) heated with a temperature controlled heating mantle produced a flowery-smelling oil, but simply blasting a can full of the same mixture with a camp stove resulted in a benzene-smelling liquid boiling at around 80 C that did not appear to react appreciably with sodium bisulfite solution.

I might have to give it a try with iron salts. I bet manganese and thorium salts work well.

Dennis A - 23-5-2018 at 00:07


Temperature control is important as you stated to avoid side products and leading to the production of benzene and not the desired ketone however i currently don't have everything at hand to start experimenting very frustrated about this however 2 weeks tops , this is a topic of great interest for me so i am eager grateful to here results and advice etc

Lazer thermometer of coarse

As for a reaction vessel currently thinking of using a 1L stainless steel fire extinguisher something quite robust and that can withstand countless reactions it contained foam which was easier to clean than the steel powdered ones i done this before and it was hell of a mess and i never managed to get the inside to be all that clean to be honest plus it rusted in a matter of days

From there with some plumbing fittings i can make a stainless steel condenser and even make a built in catalyst bed if this is what yields and purity require

The solidified mass after the reaction : Use a 0.5" pointed one end stainless steel bar through the neck and a hammer it , Hell even drill it into pulverized bits if you want

Or would a shorter but wider vessel be better for surface area making the ketone easier to distill ?

I believe magnesium salts were mentioned on hyperlab along with barium salts however there wasn't experimental details just discussion the forum its a nightmare to navigate having to constantly translate everything however the quality of information there speaks for itself

Thats all i can think of for now please anyone reading that knows more about this reaction or has details please share them here

Best regards


JJay - 23-5-2018 at 08:15

I'd be pretty reluctant to submit a fire extinguisher to vacuum distillation (won't it get crushed?), but it wouldn't be hard to fabricate something with plate steel and large-diameter iron pipe. That stated, I can't really recommend the calcium salts route and have no plans to try it again anytime soon, but it does work.

Oh and at no point did I notice any acetone in the distillate; when I used vacuum distillation, the acetone was likely all pulled into the water aspirator. When I used flame heat, I ran the distillation rather fast, with smoke flowing out of the apparatus into a PVC hose leading directly into the ventilation duct in order to prevent flammable concentrations of vapors from reaching the flame. I'm guessing that the acetone simply overwhelmed the condenser and got sucked outside. There was a small water layer both times, probably due to slightly incomplete drying or hygroscopicity.

One other thing - benzene is a known carcinogen, and purposely smelling it is never recommended.

[Edited on 23-5-2018 by JJay]

zed - 24-5-2018 at 17:01

Guys used to use Benzene to rinse off their hands.

Promotes certain types of Leukemias. Worse, serious exposure can cause aplastic anemia:

May kill your bone marrow, and thus kill you.

Still, on my list of fears, Benzene is way down the list.

[Edited on 25-5-2018 by zed]

Dennis A - 24-5-2018 at 23:37

Constant usage of cigarettes is more harmful than small exposures one seasonable individual would expect to get from moderate benzene handling any idiot who wants to wash their hands must either hate their life or believes they simply have to much time left and wants to speed this process painfully by death from dangerous disease

Leukaemia is primarily the result of the modern world go back through history and check the rates difference calculate it based on population increase and you will see some shocking results plus environmental disaster known to us and unknown plus fracking and benzene (not solely) go hand in hand flammable water coming out of peoples kitchen taps if you would even think to see if its flammable before drinking it that is but maybe the concentration just isn't enough that day , Getting the constant exposure to petroleum oil based plastics in our food is truly ridiculous anyway getting to political

Back on topic fire extinguishers are incredibly safe just the word screams safety doesn't it ?

Remember these pressurised vessels are often found in public places schools library's etc . I understand the principles of vacuum and pressure are not the same however as a result i still have no doubt that any problem would arise from " mild " vacuum being to such a vessel i trust it over glass to be honest however i often find myself pushing into the unknown and have suffered painful consequences as a result however you are free to decide your opinion but experiment is king

JJay - 3-7-2018 at 14:01

Chem Player did this recently:

It looks like you can actually use flame heat as long as you don't go full-kilter with it.

Corrosive Joeseph - 3-7-2018 at 19:22

Quote: Originally posted by byko3y  

"Decarboxylation Studies. II. Preparation of Alkyl Phenyl Ketones"
J. Org. Chem., 1963, 28 (3), pp 879–881
DOI: 10.1021/jo01038a521

Uploaded here already -
'propiophenone from calcium propionate and calcium benzoate'


draculic acid69 - 15-8-2018 at 06:47

I think these rxn's are better run in steel vessels or modified paint/solvent tins.
glass is no good for the temps needed (450'c ish for calcium salts) and the residue can fuse to the glass causing cracking as it cools.look at the NaOH/benzoate to benzene method.maybe the fe salts can be done in glass ( article says 180'c ish) but what kind of residue is left after the distillation.ppl who have successfully done these rxn's w/lead found steel vessels and a slight vacuum increased yields by helping pull the product over From the lava like conditions,I imagine it would help when doing calcium or iron variations as need to use expensive fragile glass for these rxn's

draculic acid69 - 15-8-2018 at 06:55

And why are you mixing iron sulfate into the salt mix.that's probably a yield killer.
Having the iron salts formed beforehand would definitely be better than hoping that sodium sulfate and iron carboxylates are formed in would probably have been better to just try distillation of the sodium salts by themselves.

[Edited on 15-8-2018 by draculic acid69]

Chemi Pharma - 15-8-2018 at 08:58

I suggest the use of a quartz balloon as I have, to do a direct flame heating into a hard to boiling mixtures distillation. The quartz piece supports 800ºC and direct propane torch or bunsen flame. No need of a steel can to do that.

I have papers dealing with calcium salts, either iron salts of carboxilic acids to do this kind of dry distillation. Rhodium tells about the use of lead salts, but I think it's too toxic and enviromental unfriendly:

Attachment: ketones from descarboxylation of calcium salts.pdf (227kB)
This file has been downloaded 435 times

Attachment: ketones from descarboxylation of iron salts.pdf (752kB)
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Attachment: Phenyl 2 propanone-descarboxilation iron salts II.pdf (752kB)
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Attachment: Phenyl 2 propanone-descarboxilation calcium salts.PDF (155kB)
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Attachment: Phenyl 2 propanone-descarboxilation iron salts.pdf (422kB)
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JJay - 15-8-2018 at 11:57

I haven't tried it in quartz. Pyrolysis of calcium benzoate and calcium acetate under aspirator vacuum in an ordinary borosilicate flask at 444 C produced a small amount of fragrant oil that was likely acetophenone.