Sciencemadness Discussion Board


Alchemist - 23-9-2002 at 14:09

My first post! Why, just to busy I guess!

Does anyone know of a way to convert Acetylsalicylic acid (common Aspirin) to Phenol. I have seen little tid bits but knowing more. Any idea's! Thanks!

madscientist - 23-9-2002 at 14:35

I haven't gotten around to doing a titration to see if this really did work, but here's my idea. Hydrate acetylsalicylic acid to acetic acid and salicylic acid. Heat the salicylic acid strongly, below its boiling point, until it ceases bubbling (salicylic acid supposedly decarboxylates when heated).

Nick F - 26-9-2002 at 13:49

Heat it with NaOH, it'll help to decarboxylate it, then fractionally crystalise the Ph-Na and treat it with HCl to get phenol.

Alchemist - 26-9-2002 at 14:11

Hello all,

Thanks Nick F.. Do you have the file, name of book, or web page you got this info from? What I am relly looking for are some steps with quantities,temp.,formula's, and etc.. If I/we can get this to work good, Phenol has many uses. Phenol can even be used to make Benzene and I need this to make Aniline!

Phenol, the hard way

Polverone - 26-9-2002 at 17:45

I doubt that you will find any detailed guides on the process of converting acetylsalicylic acid to salicylic acid and then to phenol. After all, it's these reactions going the other way (phenol -> sodium phenolate -> sodium salicylate -> salicylic acid -> acetylsalicylic acid) that are important from a historical and commercial perspective.

However, since the Kolbe synthesis of sodium salicylate is conducted under high pressure carbon dioxide at somewhat elevated temperatures, we can infer that tilting the equilibrium the other way (by heating sodium salicylate under atmospheric pressure in ordinary air) will cause the salt to revert to sodium phenolate. The phenolate can then be treated with acid to obtain free phenol.

Do you ever buy chemicals online? Because I can tell you where you can just order aniline, benzene, and phenol.

Nick F - 27-9-2002 at 02:59

Sorry, but no, I don't know the name of the book I read it in. It was just a general organic chemistry book. It said that most benzoic acids could be decarboxylated into the corresponding substituted benzenes by heating with a strong acid or a strong alkali.
It also said that heating phenol with Zn produced benzene.

It would be simpler just to order it, if you can...

madscientist - 27-9-2002 at 04:17

Benzene can also be prepared from toluene and anhydrous aluminum trichloride.

Easier way for benzene

PrimoPyro - 27-9-2002 at 04:34

You can also use AlI3 instead of AlCl3 as the Friedel-Crafts catalyst for that reaction.

The products are very easily seperable via distillation, as the products are benzene and mesitylene.

If anyone can get ahold of an acetylene tank, all it takes for benzene is catalytic CuCN to cause trimerization of acetylene to benzene.

Oh, and Ca(OH)2 is the best hydroxide for decarboxylation as far as I know.


Alchemist - 27-9-2002 at 06:25

Hello all,

thanks to everyone! This is all good info. I like the Benzene from Tolulene, has anyone tried it? Also where have you seen this published. I have looked in a lot of Organic Chemistry books and the web also, but have never seen this reaction! Again thanks a million.


PrimoPyro - 27-9-2002 at 09:09

Its a simple Friedel-Crafts reaction in which the methyl group on toluene gets scrambled onto other toluene molecules in the meta positions, forming two moles of benzene and one mole of mesitylene.

I have no ref for it, but Osmium brought it to our attention at the Hive, and personally, to me, his word is gold. If he says it works, then it works. My faith is in short supply these days, and I am able to take whatever he says for truth as is. That's how smart he is. Heh.


Marvin - 19-10-2002 at 20:51

Benzene from asprin sounds tortuous, salicylic acid can be decarboxylated to phenol is reasonable yeild, and so far as I know CaO or Ca(OH)2 with a little NaOH is indeed the best method. Turning phenol into benzene by the zinc route sounds tortuous though. The yeilds are probably very crappy.

In the US you should be able to buy benzoic acid, or sodium/potassium benzoate, decarboxylation produces benzene directly, no fractionating needed.

It might be better to nitrate first, then decarboxylate to nitrobenzene, and then do the reduction to aniline. Just some thoughts.


Alchemist - 20-10-2002 at 15:47


I have come to the conclusion you are right! I do live in Calif., but can not find Benzoic Acid antwhere. If you know where I can find it please let me know. Thanks...

P.S., Phenol from Aspirin is still a good one though as Phenol has many uses also.

P.P.S., Can Aspirin be decarboxylated directly or does it have to be converted to Salicylic Acid first? Has anyone tried this! If NOT I will try it as soon as I get some FREE time.

[Edited on 25-8-2005 by Ramiel]

madscientist - 20-10-2002 at 17:08

I suppose benzene might be prepared by pyrolyzing benzoic acid?

If you're looking for aniline, here's an idea for preparing it that I am about to try myself. First, prepare benzoic acid. React the benzoic acid with urea to form benzamide (or react the benzoic acid with an alcohol in the presence of sulfuric acid to yield an ester, then react with ammonia to form benzamide). Benzamide isn't much more water-soluble than benzoic acid. Then react the benzamide with calcium hypochlorite - that should yield aniline.

rikkitikkitavi - 27-10-2002 at 12:55

bensoic acid molten together with soda-lime releases benzene.

Phenole can be synthesised from toluene which first is oxidized to benzoic acid.

The latter is converted to phenole by a copper-catalyzed oxidation with air in the molten phase at 220-250 C.
(from Ullmann)


KABOOOM(pyrojustforfun) - 3-11-2002 at 18:15

I translated this procedure from my Practical Organic Chemistry (by an Iranian):

[102-95-2] C6H5OH -- work No 88


1867.3.219 Degener,J.Pract.Chem.1878 (2) 17.344

sodium benzenesulfonate 20 g
caustic soda(NaOH) 35 g
First the NaOH is dessolved in 5 cm3 water in a nickel crucible and is heated and then the finely powdered solfonate salt is added the mixture's temperature shouldn't raise more than 250°C while stirring and performing. after it reached to 250°C, tempreture should be lowered. at first the molten mixture is in a paste form later it will become fluid and its color will change from yellow to brown. at the end (after 1 hour) it is turned into the first state. after cooling, the molten substance is dissolved in a small volume of water and the red alkaline solution which contains sodium phenate and a lot of NaOH is acidified with concentrated hydrochloric acid at low temperatures. Phenol is removed in a yellow oil form and is extracted 3 times with ether. the solution is dryed with anhydrous sodium sulfate. The ether is removed by a hot water bath. It is then distilled (boils at 185-175°C) it is observed as a colorless liquid while heating and as a solid while cooling. Yield= 6-7 g.

C6H5SO3Na + NaOH ====> C6H5ONa + NaHSO3

C6H5ONa + HCl ====> C6H5OH + NaCl

sorry for my bad translation but some parts of the text are really confusing.

snop - 2-12-2002 at 13:00

In my contry 1000ml of Phenol (in polish langueg Fenol) cost 3 $ :-), and we don't have any problem of buy thish chemical : D

(hmm ciekawe czy na tym forum kuma cos polski jezyk khe :-) )

Madog - 20-1-2003 at 18:49

today i took 5g ASA and added it to some water, i boiled it down, it crystalized, then i put the heat down and melted the stuff(SA) it bubbled, gave off nasty chokeing fumes, and then i let it cool, i got 1.5g of product, sticky, melts at around 40C

fluffy bunny - 21-1-2003 at 04:45

Im confused. Someone sugggested turning, toluene to benzene with AlCl3, via the Friedel-Crafts reaction. However i thought that the friedel-Crafts reaction was the adding of an alkyl group to a benzene ring, using benzene, an alkyl halide and AlCl3 (as a catylist) not to take an alkyl group away!? :

perhaps misnamed?

Polverone - 21-1-2003 at 20:34

The reaction stated does occur, but I'm not sure the name Friedel-Crafts should be applied to it. Apparently this general reaction (conversion of Ar-R to Ar-H via Lewis acid) goes tertiary to secondary to primary alkyl groups in order of difficulty - so primary alkyl groups (like the methyl in toluene) are the hardest to remove. I found this by browsing March's Advanced Organic Chemistry, but it did not give specifics of the reaction conditions. They may be unmanageably extreme for home experimentation.

Madog - 22-1-2003 at 11:39

hey, yesterday i did hte same experiment as before useing 10g of ASA and got 4 grams of shinny, translucent, brown(i cooked it a little too long) product, melts very easy, i used my hands and a lighter to make it into one mass

it is hard at room temp, the other product is stickyish at room temp and its a tarnished off white. the other product is less consistant in apearance

if u wanna know whether what u have synthesised is phenol...

KABOOOM(pyrojustforfun) - 30-1-2003 at 18:57

Phenol from dimethylketone

Praetorian - 1-2-2003 at 08:31

I have investigated the aldol reactions of carbanions leading to phorone. Hence a I met the mesithylene, via acid aldolisation of dimethylketone. I think, it's wonderful. From common aliphatic chain we can obtain stuff with aromatic centre (is it right in English?)...reaction of dimethylketone with sulphuric acid really works, I have tried it. Thus why not to try convert mesithylene (1,2,3-trimethylbenzene) to phenol. In my opinion it should be managed by powerful oxidation (acidulated CrO3), than dekarboxylation under heat and... I don't know how it could be completed.
Has anybody a solution?

Chris The Great - 25-9-2006 at 19:12

Any results on the phenol here? I found this thread looking for other stuff, and I left some ASA on the stove to long, got lots of acetic acid fumes and thick brown goo... So I thought I'd ask if this mystery has been sovled. If not I will try a few of the above tests on my product, because if it worked I'm not going to bother extracting more ASA if phenol will work too...

matei - 26-9-2006 at 07:59

The synthesis of benzene from toluene catalyzed by AlCl3 is called transalkylation and was used in the petrochemical industry to produce benzene, but nowdays it's been abandoned because toluene is more valuable than benzene. This reaction works (yielding benzene and mesytilene) because the alkylated benzenes are more reactive in SE reactions than benzene itself (it's kind of reversed Friedel-Crafts).

not_important - 26-9-2006 at 16:23

This sort of reaction is also partially driven by fractionating off the benzene from the reaction mixture during the reaction.

leu - 26-9-2006 at 16:23

JACS 86 2846-50 & 2851-7 (1964) discuss the transalkylation and disproportionation aromatic reactions in some detail :)

Attachment: (207kB)
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solo - 26-9-2006 at 21:50

Reference Information

Thermal decomposition of acetylsalicylic acid (aspirin)
Y. Asakura Ribeiro”, A.C.F. Cairesb, N. Boralleb, M. Ionashirob
Thermochimica Acta 279 (1996) 177-181

The thermal decomposition of aspirin in air and dry air flux was investigated. Thermog- ravimetry-derivative thermogravimetry (TG-DTG), differential scanning calorimetry (DSCI, nuclear magnetic resonance (NMR), infrared absorption spectra and thin layer chromatography have been used to study the thermal decomposition of this compound. The results permit the identification of some compounds revealed in the first step of the TG-DTA curves, and also suggest the thermal decomposition mechanism.

Keywords: Acetylsalicylic acid; Differential scanning calorimetry; Infrared absorption spectra: Nuclear magnetic resonance; Thermal decomposition; Thermogravimetry

Attachment: Thermal decomposition of acetylsalicylic acid -aspirin .pdf (272kB)
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jimmyboy - 27-9-2006 at 13:52

just check Vogel's ... probably still the best way to make phenol in a lab - its a long route though but i think the yield's are high all the way through -- get benzene from toluene and start from there

toluene -> benzene -> nitrobenzene -> aniline -> phenol

solo - 27-9-2006 at 15:29

Reference Information

The Mechanism of the Copper-Induced Pschorr Cyclization. A New Phenol Synthesis Involving Hydroxylation of the Intermediate Radical by Cupric Ion’
Journal of Organic Chemistry yr:1967 vol:32 iss:12 pg:3844

The copper-catalyzed decomposition of aryl diazonium salts at low temperatures has been shown to yield an aryl radical and has been utilized to effect essentially unidirectional (a) Pschorr cyclizations, (b) hydroxylations, and (c) reductions. Excellent yields of the following products are obtained when the cuprous oxide catalyzed decompositions of Zdiazobenzophenone tetrafluoroborate are carried out under the conditions specified: (a) fluorenone, in dilute aqueous acid; (b) 2-hydroxybenzophenone, in dilute acid in the presence of a large excess of aquated (cupric ion; and (c) benzophenone, in dioxane. Analogous results are obtained in decompositions of 2-(o-diazobenzoyl)naphthalene tetrafluoroborate; a-ring closure to give benzo -fluorenone exceeds p-ring closure to give benzo-fluorenone in a 9: 1 ratio at low temperatures. These results are discussed in terms of the mecha- nism of the copper-catalyzed reaction which, contrary to suggestions in the literature, does not involve a cationic component. The oxidation by cupric ions of aryl radicals generated by diazonium ion decomposition constitutes a promising new method for the introduction of hydroxyl groups into aromatic nuclei. This method leads to high yields of phenols and no “diazo resins” which accompany the thermal production of phenols from diazonium salts. Phenols which could not be previously prepared from the corresponding amines are accessible by this new procedure. Evidence is presented that this reaction does not involve a phenyl cation intermediate but instead proceeds by transfer of H20++ from the hydration shell of the cupric ion to the aryl radical (ligand radical trans- fer).

[Edited on 27-9-2006 by solo]

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Chemguy - 27-9-2006 at 18:46

The easiest way to make phenol from ASA, is to heat it in H2SO4 for a while.

not_important - 27-9-2006 at 19:28

Originally posted by jimmyboy
just check Vogel's ... probably still the best way to make phenol in a lab - its a long route though but i think the yield's are high all the way through -- get benzene from toluene and start from there

toluene -> benzene -> nitrobenzene -> aniline -> phenol

toluene -> benzene either the FC methyl exchange that uses AlCl3, not OTC so must be made, or via two step tol->benzoic acid->benzene, where benzoic acid is harder to decarboxylate than salicylic acid. Difficult to do better than 4 toluene -> 3 benzene + 1 durene, or 75%; more typically 3 tol -> 2 benz + 1 mesitylene, yield is 2/3. Anhydrous conditions needed.

benzene -> nitrobenzene : nitrates and bisulfates needed as a minimum, some people have a difficult time finding nitrates. yields are good, especially if undernitrated and unreacted benzene is recycled.

nitrobenzene -> aniline : OK, this one is easy, iron and acid will do, yields are good.

aniline -> phenol : nitrites are often hard to obtain, and must be made from nitrates. Clean sulfuric or phosphoric acid needed, I'm not sure if you can get away using bisulfate. Yields are fair to good, using Norris' example 20 g aniline gives around 15 g phenol, roughly 75%.

Overall, maybe 50% yield top for start-to-end, using equal mole amounts of nitrate, nitrite, more than 2 moles of acid.

Direct decarboxylation needs 2+ moles of hydroxide, which can be done using sodium carbonate or bicarbonate, and slaked lime. Say 2 moles each Na2CO3 and Ca(OH)2. If you grind the residue with lime - either Ca(OH)2 or CaCO3, ignite in air, cool, and boil with water you recover low grade NaOH which can be used for the next batch.

OTC Asiprin and from-the-garden chalk/lime in, phenol out; some OTC NaHCO3 or Na2CO3 needed for makeup. Yields are not great, but you can run the reaction in a piece of pipe.

Copper often catalysis such decarboxylations.

Another route would be toluene -> benzoic acid -> benzamide -> aniline -> phenol. Polystyrene scrap can replace toluene, there are some catalysed air oxidation routes the might be usable. Reduces the amount of nitrate needed.

matei - 29-9-2006 at 13:04

I think the easyest method for obtaining phenol from benzene is by heating the sodium salt of benzenesulphonic acid (which can be made from benzene and H2SO4) with NaOH. (Vogel's 5th Ed., p. 971 - the method described is actually for 2-naphtol, but can be used for phenol too).

hell-fire - 30-9-2006 at 00:52

Phenol/ phenol sulfate can be synthed from asprin. First extract the acetyl salicylic acid from the asprin using acetone then let it dry. Messure out 100ml of H2SO4 and heat it to about 70°C. Keeping the H2SO4 at 70°C slowly add 20g of acetyl salicylic acid bit by bit. Once all the acetyl salicylic acid is added the mixture should be a nasty dark colour, the reaction goes from phenol to phenol sulfate.

There's also the possibility of going from benzaldehyde to phenol but that just seems like a waste fo benzaldehyde.

not_important - 30-9-2006 at 07:34

Originally posted by matei
I think the easyest method for obtaining phenol from benzene is by heating the sodium salt of benzenesulphonic acid (which can be made from benzene and H2SO4) with NaOH. (Vogel's 5th Ed., p. 971 - the method described is actually for 2-naphtol, but can be used for phenol too).

It's fairly easy, but good yields are a little tricky. First, getting good conversion of benzene may take very strong to fuming H2SO4, or using the prefered method of passing benzene vapour through the 98% acid at 130 to 150 C but stopping before the point of forming too much sulphone.

The alkali fusion stage is simple in concept, but not always easy to get satisfactory results from. The fusion mix is susceptable to air oxidation, yet must be well stirred. Using KOH or mixed sodium/potassium hydroxides is preferred.

And you need to get benzene to start with, as I said earlier going from toluene means no better than 75% conversion and likely 2/3 or less.

On a small scale the decarboxylation of phenol seems to give yields around that of the sulphonic acid fusion, with less overall reagent cost and without having to deal with benzene. Including starting with toluene may put the decarb route on top.

crazywantabies - 16-3-2011 at 05:10

I have search the U.S. over. Finding Phenol Crystals is hard for me, yet if one can help.?

(I speak in lieu of part time job, pt. managers, slow stickers on vehicles bumpers, and the box, for many (8) years

crazywantabies - 20-3-2011 at 09:27

Aspirin today has a couple other things. Easy, as the one said, to FRACTIONAL crystalize the aspirin [after boiling with a tad of sodium hydroxide], and with only about 20 millileters of boiled down asprin, put it on a metal plate and heat it outside until you get what looks like three different crystals. Test each crystal you got from light heating on stell pan with :)iron iii chloride (easy stuff to make too), and the PURPLE-BLUE is PHHHHHHEEEOL!!!! PRAISE THE LORD ALMIGHTY AND that one with this FRACTIONAL crystalizing method.I speak in liue of part time jobs only, slow bumper stickers, THE BOX, and Future consiousness sin detection unit for 8 years.

crazywantabies - 20-3-2011 at 09:34

WHOOPS, forgot to say, "After boiling it down slowly on a steel plate outside, add a little HCl, about one capfull for every four or so capfulls of crystals that you gotta seperate on your steel pan (don't worry, these crystals with slowly heating will seperate themselves on that pan) and let it stand a long time. THEN test with Iron III CHLORIDE. pTL, part time and saying it to all for 8 years.

crazywantabies - 20-3-2011 at 19:08

ok, last time, gotta add some CaO with your Sodium Hydroxide when you first decarboxylate salicylic acid like Marvin said. Otherwise, the salicylic acid from the aspirin will evaporate with the acetic acid as you heat it. THEN, you can fractionalize it on a pan, (waxy stuff, medium waxy stuff, and aspirin looking sticky stuff). Last, slap a little HCl in there to deacidize it. ok, sorry for the bum steer. :( That should do it. :)

AndersHoveland - 22-3-2011 at 18:20

I know this is somewhat of a different topic, but I found the following reaction to be very interesting: