Sciencemadness Discussion Board - Phthalic acid synthesis

Phthalic acid synthesis

reactofurnace - 12-6-2020 at 02:30

Can anyone suggest how to synthesize phthalic acid using a naphthalene precursor. Wikipedia makes mention of the oxidation of naphthalene using dichromate. Can anyone provide reaction conditions for this? and what solvents are best to use. Is this an oxidative cleavage type rxn, if so does anyone know the mechanism.

Also saw this route to making phthalic acid from naphthalene: https://www.prepchem.com/synthesis-of-phthalic-acid/
But the procedure seems relatively dangerous and out of my comfort zone for a home prep.

Syn the Sizer - 12-6-2020 at 04:46

Hello, I am sure it is similar to oxidizing xylenes. It can also be done using KMnO₄ as a less toxic alternative. When you oxidize naphthalene, it should oxidize the first carbons off the benzene ring creating 2 carboxylic groups.

Here are a couple links to videos, one is oxidizing o-xylene and the other oxidizing xylenes and separating the o isomer.

https://www.youtube.com/watch?v=PAARYmBYudg
https://www.youtube.com/watch?v=w5VDZI09Z00

Fery - 9-4-2021 at 05:40

Our forum member Prepic asked me to post the preparation of phthalic acid from naphtalene + KMnO4.
There are already 3 old threads discussing the same topic:
https://www.sciencemadness.org/whisper/viewthread.php?tid=65...
https://www.sciencemadness.org/whisper/viewthread.php?tid=87...
https://www.sciencemadness.org/whisper/viewthread.php?tid=17...
I don't wan't to open new thread for that so I post it here. I would like to kindly ask moderator(s) to eventually move to appropriate place / merge / split etc.

Here the method which I used long time ago - scanned page from the book and its translation into English:

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naphtalene 2,6 g (0,02 mol)
KMnO4 16g (0,10 mol)
conc. H2SO4 (I certainly used diluted accumulator 38% H2SO4 because as 15 years young boy I hadn't access to conc. acid... well I had 1 L bottle thank to my schoolmate, but also plenty of accumulator acid which was possible to buy in drugstore, so certainly used accumulator acid keeping concentrated acid to experiments where diluted couldn't be used)

In 250 ml RBF with condenser attached (I suggest Liebig with wide tube and not too long, certainly shorter than your longest glass rod) is heated mixture of 2,6 g naphtalene, 16 g KMnO4 and 160 ml of water. It is heated until disappeareance of violet color of KMnO4 (this is hard to observe as MnO2 prevents to see the color of water solution, it is necessary to let MnO2 to settle a little and observe the clear liquid above it) and until the liquid loses color above the settled MnO2 (1,5 - 2 hours). It is necessary to periodically stop the water circulation through condenser and push sublimed naphtalene back into the flask using glass rod. After finishing heating MnO2 is filtered out, filtrate boiled down to 1/3 of its original volume (to approximatelly 60 ml), 4 ml of conc. H2SO4 is added (I certainly added equivalent amount of 38% H2SO4 and boiled the volume to 50 ml as the volume of the diluted acid was bigger than concentrated acid). While still hot the paste of MnO2 is added until it dissolved (IIRC not too much of it dissolved and the solution soon started to contain suspension of MnO2 particles). Already during the addition the phthtalic acid starts to precipitate in a form of crystalline product. Reaction mixture is heated to boil and such amount of water is added which dissolves the precipitated product. After finished oxidation a little of active charcoal is added and hot solution is filtered. Filtrate is concentrated and let to crystallize. Phthalic acid crystallizes in a form of white crystals, which are sucked off and dried between 2 sheets of filter paper. By its sublimation is its anhydride is obtained, m.p. 128 C. Yield 2 g which is 60,6% of theory. Phthalic acid is white crystalline substance with m.p. 203 C, only very slightly soluble in water, soluble in alcohol, little in ether.

As I did not have camera that time, I don't have pictures of the experiment itself. But I remember I "cooked" the reaction on a wood stove in my gradma summer kitchen, so the boil was only very mild, certainly not vigorous. I also remember, that I waited for KMnO4 discoloration for maybe 4-5 hours and only then realized, that it already reacted and violet color was gone, maybe already hours ago, just the colorlessness was not visible due to MnO2. I also suggest not to boil it too vigorously as then naphtalene sublimes faster. Also stirring should improve performance (mg. stirrer or at least swirling the apparatus using hand - I did that manual swirling occasionally as melted naphtalene is as a top layer and it is necessary to increase surface contact to made it to react). Maybe the boil itself is sufficient to mix both phases, but vigorous boil = too fast sublimation of naphtalene which settles in condenser. I wonder whether it couldn't be performed in a flask without condenser, sitting on mg. stirrer (or at worst periodically swirl in a hand) with its neck just covered by a plastic foil, at such temp just below the boil (e.g. in boiling water bath so the content in flask couldn't reach 100 C), so the plastic foil keeps the flask closed and prevents naphtalene loses by escaping.
I still have the vial with the product, the vial is 10 ml. Pictures made just now attached. The label is still readable although it already lost some color and the paper is somewhat yellowish.

I found solubilities of phthalic acid in water here:
https://www.bc.edu/content/dam/bc1/schools/mcas/Chemistry/pd...
"Phthalic acid is very soluble in boiling water, 18 g/100 mL, and is much less soluble in chilled (14°C) water, 0.54 g/100 mL."

[Edited on 9-4-2021 by Fery]

Fery - 3-5-2021 at 04:27

Here I found oxidation of naphtalene with KMnO4 + H2SO4 in acetic acid : H2O 1:1
https://www.researchgate.net/publication/312117264_Kinetic_a...
https://www.researchgate.net/profile/Bijudas-K/publication/3...
this study focused not on yield but on mechanism and reaction speed
acetic acid dissolves naphtalene better than water
worth of trying for producing phthalic acid and focusing on yield
Attachment: 40-0581116.pdf (591kB)
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the bad solubility of naphtalene in water really annoyed me decades ago (2 phases = bad contact of molten naphtalene floating on top of the oxidizing solution) and also crystals of naphtalene in condenser (maybe if using enough acetic acid naphtalene would be dissolved by acetic acid in the condenser)

here comparison with KMnO4 alkaline oxidation to phtalonic acid instead of phtalic acid:
https://sci-hub.st/10.1021/j150083a001
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also interesting oxidation to phthaldehydic acid instead of phthalic acid here:
http://www.orgsyn.org/demo.aspx?prep=cv2p0523
http://www.orgsyn.org/Content/pdfs/procedures/cv2p0523.pdf
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Triflic Acid - 3-5-2021 at 07:04

An interesting thought just popped into my head. What if someone where to put a catalytic amount of of dichromate into an acidic solution of whatever they wanted to oxidize and then bubbled ozone or something through the solution, so only a bit of dichromate is needed. Saves on the cost, and still has the ease of a Jones oxidation. No manganese oxides or expensive amounts of chromates.

Oxy - 3-5-2021 at 09:41

Ozone is nasty gas and I would avoid it if possible. Despite it's toxicity the products of organics reacting with it may be explosive and toxic also.
What else - you can't really control the reaction as you don't know if your substrate is reacting with ozone or dichromate.

However it is easy to do when passing electric current through the solution. You can then use a relatively small amount of oxidizer (like Ce4+) which will be continuously regenerated

Triflic Acid - 3-5-2021 at 10:10

Yeah, the electric current method seems smarter.

Fery - 3-5-2021 at 23:30

And acetic acid is quite good solvent for naphtalene and also for some ions, worth of trying the electrolysis...

Keras - 15-11-2024 at 11:11

I’m waking up this thread just to know if someone has tried another strong oxidiser? I can’t really have access to potassium permanganate so I'd rather spare what I have. Potassium dichromate I would have to make, and I'd rather avoid chromium VI completely for evident reasons of waste management. I was thinking about Oxone™, i.e. potassium peroxymonosulphate, because I have tons of it. Did anyone tried?

Fery - 15-11-2024 at 12:12

Keras where do you live? I have certainly more than 10 kg of KMnO4.
I did oxidation of naphthalene with CrO3 in acetic acid into 1,4-naphthoquinone.

Keras - 15-11-2024 at 12:47

In France.

I have CrO₃ flakes, but really each time I open the bottle they're stored inside, I recoil instinctively

Keras - 25-11-2024 at 08:33

Ok so I tried this morning oxidising 1 mmol (~ 100 mg) of naphthalene with 5 mmol (~ 800 mg) of potassium permanganate. Rationale is, you oxidise four carbons with two oxygens each, so each molecule of permanganate gives up two oxygens, ergo one needs at least four times as much permanganate as naphthalene.

Naphthalene dissolved in DCM (a few drops are enough) in a 25 mL RBF with dropping funnel and reflux condenser (useless, in hindsight). Heated until the DCM boils, dripped in the permanganate (~15 mL + 2 mL 50% sulphuric acid). Probably almost instantly particles of manganese dioxide stuck to the wall of the flask. Continued stirring for one hour at 70 °C. Dismantled the thing, geared up for vacuum filtration. No traces of sublimated naphthalene. No real smell, too.

Assuming 100% yield, 1 mmol of phthalic acid weighs 166 mg, soluble in 30 mL of water, especially hot. So I put a bed of Celite™ to avoid clogging my sintered disc with particles of manganese dioxide and got a clear, straw yellow filtrate. No trace of DCM, no purple colour, so I guess all the permanganate had reacted.

Boiled the ~30 mL of water down to 10 mL. Put it in the fridge → Nothing. Yellow water, is all. Faint aroma of something decisively different from naphthalene, but zero product.

I’m not sure what happened. Could all naphthalene have been oxidised to carbon dioxide? Did I use too much permanganate? Bad solvent? No idea at this point.

Going to retry later in the week using other oxidising products: Oxone, sodium percarbonate, bleach, ammonium persulphate.

PS: Cleaning the flasks and stir bar is easy using HCl which dissolves manganese dioxide.

[Edited on 25-11-2024 by Keras]

Fery - 25-11-2024 at 11:50

I did the oxidation of C10H8 with 10% KMnO4 water solution. At oxidation state no DCM, no H2SO4. It ran well. I posted it here:
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
The disadvantage is processing quite voluminous MnO2 by repeatedly extracting with hot water and filtering on Buchner.

Keras - 25-11-2024 at 22:59

There are several elements I don’t understand:
– You did the oxidation in neutral pH, didn’t you? I thought cleavage worked only in acid conditions?
– Why acidify the resulting mixture at the end? On the contrary, I would’ve basified the mixture to get soluble sodium phthalate, filtered out all manganese dioxide and then reacidified the filtrate to get the free acid.
I’ll retry with the amounts you suggest, only 10 times smaller.

Keras - 25-11-2024 at 22:59

There are several elements I don’t understand:
– You did the oxidation in neutral pH, didn’t you? I thought cleavage worked only in acidic medium?
– Why acidify the resulting mixture at the end? On the contrary, I would’ve basified the mixture to get soluble sodium phthalate, filtered out all manganese dioxide and then reacidified the filtrate to get the free acid.
I’ll retry with the amounts you suggest, only 10 times smaller.

[Edited on 26-11-2024 by Keras]

Gualterio_Malatesta - 26-11-2024 at 01:48

Quote: Originally posted by Keras

Boiled the ~30 mL of water down to 10 mL. Put it in the fridge → Nothing. Yellow water, is all. Faint aroma of something decisively different from naphthalene, but zero product.

[Edited on 25-11-2024 by Keras]

Isn't it supposed to be in a form of dipotassium o-phthalate (as someone mentioned here on the forums) after the oxidation reaction? And it should be acidified to yield phthalic acid which is insoluble in water.
If so, would it be possible to add ascorbic acid, which will make MnO2 dissolve in water and phthalic acid then percipitated by HCl solution? Gets rid of filtering pesky MnO2.

Gualterio_Malatesta - 26-11-2024 at 02:11

Quote: Originally posted by Fery

While still hot the paste of MnO2 is added until it dissolved
[Edited on 9-4-2021 by Fery]

What I don't get in Fery's write-up is why did he have to filter out MnO2 only to add it back again? Wasn't the reaction finished already?

Keras - 26-11-2024 at 03:12

Quote: Originally posted by Gualterio_Malatesta

Quote: Originally posted by Keras

Isn't it supposed to be in a form of dipotassium o-phthalate (as someone mentioned here on the forums) after the oxidation reaction?

In this case, I had added sulphuric acid to the permanganate solution, and I checked that the pH was at most 1 before filtering. There was a priori enough water to dissolve the phthalic acid almost completely:

22 mmol/L @ 0°C, 35 mmol/L @ 20 °C, 640 mmol/L @ 95 °C

I had about 15 mL of water (before rinsing) so that should’ve contained at least 500 µmol or 87 mg of product. Not much, but enough to form a visible precipitate.

Sir_Gawain - 26-11-2024 at 05:40

Working with sub-gram amounts, it’s very easy to lose your product (or volatile reactants). 87 mg is such a tiny amount it’s not surprising you didn’t get any product. It’s also possible that the acidified permanganate solution was to harsh of an oxidizer and simply oxidized to CO2. If I have some free time this week I’ll try this reaction myself.

Keras - 26-11-2024 at 07:25

Quote: Originally posted by Sir_Gawain

Working with sub-gram amounts, it’s very easy to lose your product (or volatile reactants). 87 mg is such a tiny amount it’s not surprising you didn’t get any product. It’s also possible that the acidified permanganate solution was too harsh of an oxidizer and simply oxidized to CO2. If I have some free time this week I’ll try this reaction myself.

My supply of potassium permanganate is very small (a few grams), and I like to work microscale (I find it cute, and it consumes less reactants). I have usually no problems, for example the nitrosation of phenol by nitrous acid works very well even at a sub-gram scale.

But yeah. I agree over-oxidation is probable. I’ll try oxidation with dilute nitric acid (37%), since apparently that pathway works for oxidising o-xylene to phthalic acid – although it might lead to nitration instead. Unfortunately I don’t have any potassium chlorate left atm.

[Edited on 26-11-2024 by Keras]

bnull - 1-12-2024 at 15:14

The yellow may be due to alpha-naphthoquinone. It also seems to be one of the side products of an electrochlorination of naphthalene in hydro-alcoholic solution of HCl I tried fifteen years or so ago. Aside from a heavy oil (which I suppose is a polychlorinated naphthalene), there was something soluble that became red when the solution was made strongly alkaline. Or maybe the naphthoquinone was formed from the polychloro-naphthalene when I added the base.

If you can spare another 800 mg of permanganate, try the procedure again, this time adding a small quantity of dichromate (the tip of a penknife will do) and no acid. Dichromate seems to catalyse oxidations by permanganate. I'm not really sure of how it works, maybe dichromate acts like an acid.

teodor - 2-12-2024 at 00:45

Quote: Originally posted by Keras

In France.

I have CrO₃ flakes, but really each time I open the bottle they're stored inside, I recoil instinctively

I use it for years (as well as chromic acid to clean glassware) and still good. There is more danger with insoluble chromates (e.g. when unexperienced people try to get K2Cr2O7 from stainless steel in a pot and usually end with a different chromates mix) which can penetrate a cell membrane and cause DNA mutation, but with CrO3 it is much less probably because in tiny quantities it reacts with surface fluids and the cell wall itself. Usual laboratory techniques and protection should be enough.
On my experience low solubility of potassium permanganate requires big flasks for mediocre yield.

[Edited on 2-12-2024 by teodor]

[Edited on 2-12-2024 by teodor]

Keras - 2-12-2024 at 01:09

Quote: Originally posted by bnull

The yellow may be due to alpha-naphthoquinone.

That’s a better assumption indeed! However, when I added sodium hydroxide in an attempt to solubilise any phthalic acid produced, no red colour was ever produced…

Quote: Originally posted by bnull

If you can spare another 800 mg of permanganate, try the procedure again, this time adding a small quantity of dichromate (the tip of a penknife will do) and no acid. Dichromate seems to catalyse oxidations by permanganate. I'm not really sure of how it works, maybe dichromate acts like an acid.

Unfortunately I have no dichromate at hand, but yeah, I guess I can still spare 800 mg of KMnO₄ before running out. I am however, currently distilling/concentrating 20° white vinegar cleaner into glacial acetic acid. It seems that oxidation of naphthalene to phthalic acid in glacial acetic acid is well documented. All the experiments I did so far used DCM and water, and that didn't seem to work well. Maybe it needs an acceptable co-solvent to work properly?

Attachment: Kinetics and Mechanism of Naphthalene Oxidation in Acetic Acid.pdf (371kB)
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[Edited on 2-12-2024 by Keras]

teodor - 2-12-2024 at 01:31

You can look https://library.sciencemadness.org/library/books/Experiments...
Page 233 for further inspiration with the acetic acid solvent.
Also, I recommend just to buy it glacial.

Keras - 2-12-2024 at 01:40

Quote: Originally posted by teodor

You can look https://library.sciencemadness.org/library/books/Experiments...
Page 233 for further inspiration with the acetic acid solvent.
Also, I recommend just to buy it glacial.

Lol, I have glacial acetic acid somewhere, I just can’t seem to be able to get my hand back on it. :/ In any case, I don’t need it glacial, the paper I joined used 50% concentration, which is easily feasible starting from 20% w/w.

teodor - 2-12-2024 at 02:02

I remeber one more point why I don't like permanganate. When its reduction is started it doesn't depend on the rate of your organic product oxidation. It just don't stop untill all permanganate is reduced (not because of the organic oxidation). I believe with CrO3 you can see the actual rate of your compound oxidation (the change of the color).
You can easily get any (di) chromate from CrO3 in situ, but CrO3 is not always a substitution for dichromate for acetic acid solvent because it doesn't dissolve in AcOH as good as dichromate. So you have to mix NaOH with it in a small quantity of water before AcOH addition in this case.

[Edited on 2-12-2024 by teodor]

Keras - 2-12-2024 at 22:53

I have no personal grudge with permanganate. Is just that it is difficult to source because it’s listed as a drug precursor over here in the EU. So you have to make it yourself from manganese oxide by the fusion process, which takes time.

[Edited on 3-12-2024 by Keras]

wg48temp9 - 2-12-2024 at 23:20

Quote: Originally posted by Keras

I have no personal grudge with permanganate. Is just that it is difficult to source because it’s listed as a drug precursor over here in the EU. So you have to make it yourself from manganese oxide by the fusion process, which takes time.

In the UK it is sold on eBay, Amazon, APC Pure and several other sites.

teodor - 3-12-2024 at 00:51

Quote: Originally posted by Keras

But you need it in the form of solution. So, you can try to use manganese sulfate + ammonium persulfate (as you planned) + silver nitrate to generate it in situ during the synthesis.
Check this thread: https://www.sciencemadness.org/talk/viewthread.php?tid=15996...

Because the synthesis will consume the permanganate there is a chance it will go to completion.
Also the rate of permanganate generation can change the synthesis, but probably it would be interesting to try. As I said, the problem with permanganate is that it can be reduced faster than the organic compound to be oxidised.

Keras - 3-12-2024 at 12:13

Lol, turns out I might’ve made manganese sulphate inadvertently. During my last experiment with naphthalene and potassium permanganate, I collected the cake obtained after reaction and filtration, which contains mainly manganese oxide, and added in it sodium hydrosulphite. It immediately cleared up and I’m now with a beaker full of a whitish powder in water. That might be it. I’ll filter it tomorrow and see.

Texium - 8-12-2024 at 08:32

While this isn’t exactly in the spirit of the thread, why don’t you just buy phthalic anhydride from a chemical supplier? S3 Chemicals has 500 g for 27 €. That seems very reasonable as you would need kilos of permanganate and a bucket scale setup to make that much.

Keras - 8-12-2024 at 09:00

Quote: Originally posted by Texium

While this isn’t exactly in the spirit of the thread, why don’t you just buy phthalic anhydride from a chemical supplier? S3 Chemicals has 500 g for 27 €. That seems very reasonable as you would need kilos of permanganate and a bucket scale setup to make that much.

Might be a good idea. It’s 57 € here which, for a commodity chemical produced at multi-ton scale, always seemed to me excessive.

Texium - 8-12-2024 at 11:22

Yeah, that is a little steep. Commodity chemical or not, selling it packaged as a lab reagent with a guaranteed level of purity will inevitably result in a markup. S3’s price at least seems reasonable in that context. I’m selling phthalic anhydride from Aldrich 500 g for $25, but the shipping to Europe would almost certainly make it a worse deal.

Boffis - 10-12-2024 at 23:02

Which country is Laboratorium Discounter based in? There web site is a bit obscure.

teodor - 12-12-2024 at 00:39

Quote: Originally posted by Boffis

Which country is Laboratorium Discounter based in? There web site is a bit obscure.

The Netherlands. But it is not the seller I can recommend, we have a separate thread where some people already shared their negative experience with them.

woelen - 12-12-2024 at 01:21

Last week I again ordered some chemicals from Laboratoriumdiscounter. I ordered a small amount of 98% hydrazine hydrate and sodium peroxodisulfate from them. I received the chemicals a few days later. My experiences with this company are quite good, but indeed, sometimes things go less smooth. My previous order took several weeks, because their supplier took a long time to deliver the chemical to them. In my experience, it is more a matter of communication (or the lack of communication) than wrong intent. I already told them this and wrote that on a review site (Trustpilot) as well.

teodor - 12-12-2024 at 06:54

Quote: Originally posted by woelen

Last week I again ordered some chemicals from Laboratoriumdiscounter. I ordered a small amount of 98% hydrazine hydrate and sodium peroxodisulfate from them. I received the chemicals a few days later. My experiences with this company are quite good, but indeed, sometimes things go less smooth. My previous order took several weeks, because their supplier took a long time to deliver the chemical to them. In my experience, it is more a matter of communication (or the lack of communication) than wrong intent. I already told them this and wrote that on a review site (Trustpilot) as well.

I really appretiate your effort to provide the constructive feedback for them. I am really glad if they are going to improve their way of business and are reading the feedbacks for that purpose. Yes, I know that they probably have no bad intentions, but at the present time this seller is the last one I can even consider when buying chemicals and glassware. As for the component in question I would better by some phthalic anhydride from S3.

The day before yesterday I've ordered potassium and ammonium persulfate from labshop.nl as well as some laboratory consumables. Yesterday it was delivered exceptionally well packed. So, I am not always prefer german companies, you see.

[Edited on 12-12-2024 by teodor]

Keras - 12-12-2024 at 07:22

Quote: Originally posted by teodor

Quote: Originally posted by woelen

…

I really appretiate your effort to provide the constructive feedback for them.

I’m used to ordering many items from LD and, yes, they are a bit messy, but I suppose this is just the result of their supply chain being unreliable. Last time I enquired about a late delivery, they told me they weren't surprised the supplier they had to source the item from was late, it was apparently usual. Then they did go great length to assuage this, they sent my items on the fly as they received it, which ended up meaning three parcels instead of just one (and I paid no extra fees, they assumed the extra two shippings cost).

Keras - 10-1-2025 at 05:55

So I tried the oxidation of naphthalene (1.3 g, 10 mmol) dissolved in 20 mL of glacial acetic acid by 6.5 g (~ 40 mmol) of potassium permanganate.

The reaction is weird. The permanganate will turn to manganese dioxide quite calmly, until there is a sudden bubbling and the temperature suddenly rises.

I was caught off guard the first time, and some of it spilled out of the beaker.

I redid it, enclosing the beaker in a bigger beaker, and filling that bigger beaker with ~10°C water. Same phenomenon, repeated twice, but this time under control, so nothing bad happened. It subsides quite quickly.

Problem: at the end I’m left with a goo/jelly of manganese dioxide mixed with acetic acid I don’t really know what to do with. I tried to filter it, but apart from messing up my Hirsh funnel, which took ½ hour to clean up afterwards, I got nothing.

Would phthalic acid steam distillate?

I can’t extract it with base, because of acetic acid.
I can dilute it until the goo is liquid, filter out the dioxide, then distill it, or extract it using DCM?

[Edit: typos]

[Edited on 10-1-2025 by Keras]

bnull - 10-1-2025 at 07:31

Quote:

Would phthalic acid steam distillate?

No. It melts at 207 °C and, for some strange reason, I can't find its boiling point. But you can distill acetic acid from the mix.

Quote:

I can dilute it until the goo is liquid, filter out the dioxide, then distill it, or extract it using DCM?

You mean diluting it with water or with acetic acid? If water, some phthalic acid will be separated along with manganese dioxide. If acetic acid, use a cotton ball tucked into the stem of the funnel.

I think that you can make ethyl esters. Diethyl phthalate boils at 278 °C, while ethyl acetate boils at 77 °C. It won't be too hard to separate them.

Keras - 10-1-2025 at 08:07

I had thought about distilling (or evaporating) acetic acid, but I'd be left with a solid chunk. Maybe I could soak it in DCM to extract the phthalic acid, decant, filter and evaporate.

Making esters could be worth it, but really I don’t want to go the extra mile for a gram or two of product.

Sir_Gawain - 10-1-2025 at 08:09

Quote: Originally posted by bnull

No. It melts at 207 °C and, for some strange reason, I can't find its boiling point. But you can distill acetic acid from the mix.

Above 200°C, phthalic acid decomposes to phthalic anhydride which sublimates at 295°C.

bnull - 10-1-2025 at 08:39

Quote: Originally posted by Sir_Gawain

Above 200°C, phthalic acid decomposes to phthalic anhydride which sublimates at 295°C.

Oh, that. I knew I was missing something. Thanks.