Sciencemadness Discussion Board - Feasibility of preparing copper phthalocyanine at home

Feasibility of preparing copper phthalocyanine at home

Arcaeca - 6-9-2019 at 17:56

It me, the guy trying to make pigments from scratch, and I've been wondering if it's possible to make copper phthalocyanine, aka "phthalo blue" at home. Well, not just possible - if I can do it with easily available chemicals and equipment and it's not absurdly dangerous.

From what understand, metal phthalocyanines are typically prepared by synthesis of phthalocyanine in the presence of metal salts (copper salts in my case, which aren't particularly hard to make, e.g. copper(II) acetate). Phthalocyanine can in turn be produced, according to Wikipedia, from heating phthalic anhydride in the presence of urea. (It also mentions being possible to synthesize from various phthalic acid derivatives like phthalamides... without actually saying how) And phthalic anhydride is... a smidge dangerous to work with, but can apparently be produced by oxidation of naphthalene (main component of old mothballs) or o-xylene (easy to get in hardware stores... or at least an unspecified mix of probably all of xylene's isomers).

That then leaves me with trying to figure out what a suitable oxidizer would be; simple 3% aqueous H₂O₂ has served me well so far but something tells me that won't be quite strong enough to oxidize an arene.

So in short, the preparation would seem to be:

naphthalene (mothballs) OR xylene (paint stripper) + mystery oxidizer --> phthalic anhydride

phthalic anhydride + urea (fertilizer) + copper acetate + heat --> copper phthalocyanine

Which raises the following questions:

Would this... even work?
What can be used for the mystery oxidizer that's as easy to get as all the other ingredients?
How much equipment is needed to do this?
Is this even remotely safe?

mayko - 6-9-2019 at 18:35

Permanganate is what I've usually seen (eg, Vogel's, p520). There is also a book in the forum library, Fundamental Processes of Dye Chemistry, which gives an air+catalyst oxidation on a pumice substrate and has a section on phthalocyanine and other stuff you'd probably be interested in.

The most amateur-friendly path to phthalic anhydride would be extracting from placticized PVC, imo

DavidJR - 7-9-2019 at 04:05

Yes, it is feasible to make at home, I've done it. It's also not an especially difficult synthesis.

Basically, you need to mix urea, phthalic anhydride, copper (II) chloride (or another salt, but that's what I used), and a catalyst (boric acid works, but ammonium molybdate is better). Then heat the crap out of it. Ammonia gas will be produced. Then dissolve the mass in water and clean up the product by repeated washings with dilute HCl, dilute NaOH, dilute HCl again, then water, then acetone.

Optionally, you can dissolve the product in conc. sulphuric acid then precipitate it by adding this solution dropwise to a large volume of water with strong stirring. This will produce very fine particles, necessary for its use as a pigment.

Even if you don't do that, filtering is kind of a massive pain in the ass. Vacuum filtration is 100% necessary. Alternatively if you have access to a centrifuge that is even more convenient.

Making phthalocyanine green from it is somewhat more difficult... I've not been able to get a good colour yet.

As for the phthalic anhydride: first, it's really not all that dangerous to handle at all. It is a skin irritant though and you'll want to avoid breathing dust.

I did once try preparing it from napthalene and permanganate but honestly all I made was a stinky mess. I also wouldn't recommend using xylenes unless you can get pure ortho-xylene.

Several folks here have extracted phthalate ester plasticisers from PVC gloves. I bought diisobutyl phthalate liquid from Limac though. In either case, the ester can be hydrolysed (I found acid hydrolysis more convenient than base hydrolysis) to get phthalic acid, which can then be dehydrated to the anhydride and purified simultaneously by sublimation. However, this sublimation step is incredibly time consuming. A better approach is to use a dean-stark trap and mixed xylenes as the entrainer.

Another alternative to hydrolysing phthalate esters is buying potassium hydrogen phthalate, "KHP", which is reasonably readily available.

Later, though, I was able to buy a kilo of phthalic anhydride from Sigma Aldrich for dirt cheap. Unfortunately, I can't order from them any more...

unionised - 7-9-2019 at 04:34

Copper phthalocyanine was originally prepared by accident.
That suggests that it can't be very difficult.

DavidJR - 7-9-2019 at 04:42

Quote: Originally posted by unionised

Copper phthalocyanine was originally prepared by accident.
That suggests that it can't be very difficult.

Actually, that's not quite true... The first phthalocyanine was indeed produced accidentally, but it was iron phthalocyanine, not copper.

This discovery was made in Grangemouth, just a few miles away from my home.

j_sum1 - 7-9-2019 at 04:59

Texium made a video on its synthesis. I forget the details but remember thinking it looked fun and not too challenging.

https://youtu.be/Mnx6PBFBGik

Arcaeca - 7-9-2019 at 05:39

Quote: Originally posted by DavidJR

Even if you don't do that, filtering is kind of a massive pain in the ass. Vacuum filtration is 100% necessary. Alternatively if you have access to a centrifuge that is even more convenient.

Damn. I don't have a vacuum pump; I've just been doing gravity filtration thus far... and not even really "filtration"; more like just "letting precipitate settle at the bottom and decanting the liquid layer into a separate jar".

But other than that, it seems like everything else should be easy enough to get; boric acid is sold in hardware stores as a roach insecticide (though I'm not sure of the purity), as are HCl, NaOH and acetone (although I already have HCl and NaOH on hand anyway).

So it still sounds like the phthalic anhydride is going to be the hard part. I found this synthesis on the wiki:

http://www.sciencemadness.org/smwiki/index.php/Phthalic_anhy...

Which again, sounds like all the necessary reactants are easy to come by... PVC, check; isopropanol, check (70% solution sold in pretty much all pharmacies); "fuming hydrochloric acid", I have a 31.45% HCl by volume (20° Baumé) mixture of muriatic acid which fumes, so I assume that that's concentrated enough... check. And the synthesis calls for PVC latex gloves, but I can't see any reason why PVC pipe wouldn't work, other than needing special tools for pulverizing it?

EDIT: Ooookay now I get what people have been meaning by "plasticized" PVC - not just as in "PVC plastic" from which many things inc. PVC conduit is made, but flexible PVC made flexible by added phthalates which is what we're actually extracting, not the PVC itself. So rigid PVC wouldn't work after all.

[Edited on 9-7-2019 by Arcaeca]

12thealchemist - 7-9-2019 at 06:25

Quote: Originally posted by j_sum1

Texium made a video on its synthesis. I forget the details but remember thinking it looked fun and not too challenging.

https://youtu.be/Mnx6PBFBGik

So did UC235:

https://www.youtube.com/watch?v=qvpK2Ie1pl0

Arcaeca - 7-9-2019 at 08:13

Uh... he's doing this in a microwave? Despite giving off ammonia and HCl gas? (Which, as he says, are *hopefully* trapped as ammonium chloride, but, yknow, if they aren't, you'd think it should be done in a better-ventilated area)

I can probably make the phthalic anhydride today, but I'm still waiting on my graphite crucibles to arrive in which to heat the crap out of the phthalic anhydride + urea + copper salt mixture, so I can't do it all in one day.

---------------

Anyway, I was doing some thinking (always dangerous) and thought it would be even more interesting to see if copper phthalocyanine synthesis could be done using only materials that don't require a complex chemical manufacturing and supply infrastructure; like if the year was 500 AD and there were no PVC gloves to extract phthalates from or industrially-produced bags of urea fertilizer, could you still make copper phthalocyanine from scratch? (Sort of the same idea as HTME on Youtube) NaOH as lye wasn't historically super hard to make (you need limestone and soda ash), urea makes up the majority of the solids in human urine, alcohol for solvent - ethanol at least, if not isopropanol - wouldn't have been hard to come by (vodka would be ideal), copper acetate just requires copper and vinegar... that just leaves the phthalic anhydride. If you can start with any phthalate and follow the same boil in alcohol/hydrolyze/acid/condense prodecure to make phthalic anhydride, then it's just a matter of finding naturally occurring phthalates... which seems easier said than done, but according to this paper:

http://www.ecetoc.org/wp-content/uploads/2014/08/ECETOC-TR-0...

"Pare et al. (1981) found as much as 0.2-0.7% dry weight (of the whole plant) of n-butyl-4-ol n-propyl phthalate in a common house plant, Sansevieria trifasciata;"

The trick is then isolating it...

DavidJR - 7-9-2019 at 08:27

Yeah apparently the microwave synth works quite well but I would not recommend doing it in a microwave that you eat out of.

When I did it, I put all of the solids in a 250ml flat bottom (spherical) flask and heated on the hotplate. Honestly you could probably just use a beaker or just about anything, no need for a fancy graphite crucible.

unionised - 7-9-2019 at 08:31

Just a thought; do you need to convert the phthalic acid to the anhydride in advance or would it dehydrate during the reaction?

DavidJR - 7-9-2019 at 12:52

Quote: Originally posted by unionised

Just a thought; do you need to convert the phthalic acid to the anhydride in advance or would it dehydrate during the reaction?

That might well work actually...

Tsjerk - 7-9-2019 at 14:33

I did something similar to the urea / di-acid in microwave reaction. I don't think there is HCl produced though.. Just ammonia. Haven't seen Texium's video though. Maybe tomorrow.

http://www.sciencemadness.org/talk/viewthread.php?tid=104964

Arcaeca - 7-9-2019 at 15:16

Well, I have PVC-coated cotton gloves sitting in hot isopropanol in a reflux bath right now to extract the phthalates. The procedure from the wiki says to hydrolyze the esters with NaOH(aq) - but if acid hydrolysis works just as well, then am I correct that I can skip that step and move straight to adding HCl to make phthalic acid, and then sublimate the phthalic anhydride straight out of that?

UC235 - 7-9-2019 at 17:31

Quote: Originally posted by Arcaeca

Well, I have PVC-coated cotton gloves sitting in hot isopropanol in a reflux bath right now to extract the phthalates. The procedure from the wiki says to hydrolyze the esters with NaOH(aq) - but if acid hydrolysis works just as well, then am I correct that I can skip that step and move straight to adding HCl to make phthalic acid, and then sublimate the phthalic anhydride straight out of that?

NaOH works much better. Phthalic acid has poor water solubility and will be extracted into an organic phase of fatty alcohol, hemiester, and unhydrolyzed ester which only reacts with the HCl on the phase boundary.

NaOH produces a soap-like intermediate from the hemiester, which emulsifies the phases and speeds the reaction dramatically. The Phthalic acid is also dissolved entirely in the aqueous phase as phthalate. You remove the upper oily layer, add HCl to crash out the phthalic acid, and recrystallize from boiling water.

[Edited on 8-9-2019 by UC235]

Arcaeca - 8-9-2019 at 09:41

So I added the NaOH and refluxee for another hour, then let the solution sit overnight to let the alcohol and aqueous layers separate, but half a day later and the boundary between them is... not obvious, to put it lightly.

(The solution has a orange-ish tint since the PVC gloves were dyed red and some of the dye leached out into the isopropanol bath. I figured it wouldn't affect much and if nothing else, since it was dissolved by the isopropanol, it would probably stay dissolved in the isopropanol when the layers separated)

unionised - 8-9-2019 at 10:40

I hardly like to ask, but how sure are you that the plasticiser is phthalate?

Arcaeca - 8-9-2019 at 10:50

I don't. But the strips of PVC-coated cotton are noticeably more rigid after boiling in isopropanol, so apparently I stripped some kind of plasticizer out. :shrug:

Arcaeca - 9-9-2019 at 20:45

Okay, I'm not sure if the phthalic anhydride can be salvaged at this point; there's still no obvious separation between the alcohol and aqueous layers, and there's some whitish precipitate that's dancing around the bottom of the jar that I would be tempted to conclude is phthalic acid, if not for the fact that I haven't actually added the HCl yet.

So I've been looking at simply ordering phthalic anhydride, but before I sink the money into it, are there any other dyes I can make with it? I've been eyeing thioindigo since it has a tantalizingly similar structure (or at least, the monomer it's made of does) to phthalic anhydride, but alas! it would require breaking up a 5-membered heterocyclic ring to replace C with S and O with C, which seems... nontrivial.

And I'm going to need to order urea, since despite being the #2 most important nitrogen-adding fertilizer after anhydrous ammonia, apparently none of the hardware or home improvement stores around me stock it. But I also have no other use for the urea besides this one project, so... is it worth it?

DavidJR - 10-9-2019 at 05:30

Quote: Originally posted by Arcaeca

Okay, I'm not sure if the phthalic anhydride can be salvaged at this point; there's still no obvious separation between the alcohol and aqueous layers, and there's some whitish precipitate that's dancing around the bottom of the jar that I would be tempted to conclude is phthalic acid, if not for the fact that I haven't actually added the HCl yet.

Try filtering off the crud that precipitated and then add HCl to the liquid until strongly acidic to see if you get a precipitate of phthalic acid.

Quote: Originally posted by Arcaeca

So I've been looking at simply ordering phthalic anhydride, but before I sink the money into it, are there any other dyes I can make with it?

Yes, actually, phthalic anhydride is an important intermediate in dyestuffs manufacture overall. For instance, you can use it to make various anthraquinone dyes too (by Friedel-Crafts acylation). Even easier (and useful in the lab too) is preparing phenolphthalein.

For me, phthalic anhydride was surprisingly cheap anyway. I got a kilogram for £13 (excl. VAT and shipping) from Sigma.

Quote: Originally posted by Arcaeca

I've been eyeing thioindigo since it has a tantalizingly similar structure (or at least, the monomer it's made of does) to phthalic anhydride, but alas! it would require breaking up a 5-membered heterocyclic ring to replace C with S and O with C, which seems... nontrivial.

Yeah, that's not going to work.

Quote: Originally posted by Arcaeca

And I'm going to need to order urea, since despite being the #2 most important nitrogen-adding fertilizer after anhydrous ammonia, apparently none of the hardware or home improvement stores around me stock it. But I also have no other use for the urea besides this one project, so... is it worth it?

Urea is dirt, dirt cheap.