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byko3y
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The yields of isatoic anhydride are essencialy the same as for anthranilic acid procedure, if the latter is done correct. For some reason there was a
1890 with a perfect procedure but nobody remembered it, so I needed to reinvent it once again.
And it's not easier to prepare an isatoic anhydride first, because you will need to separate the anrthranilic acid somehow, and this way the procedure
becomes even thicker to perform than the straight one.
As mr wack and me already wrote, you need to precipitate copper salt - it's the best way to separate anthranilic acid from anything.
Gonna write an answer to the isatoic thread describing the reaction mechanism according to patents US 3,867,951 and US 4,328,339.
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Quote: Originally posted by Cheddite Cheese  | | The isatoic anhydride synthesis you posted seems a lot like the synthesis of anthranilic acid (and you did observe some anthranilic acid produced, you
say). How is it different, in terms of conditions and mechanism? |
This is a good question. I was wondering this too, but I think the differences are in the details. The temperature ranges are more extreme.
In a 250ml Erlenmeyer mix 80ml H2O and 8.0g NaOH, cool to about +5°C and don't mess with it until later. To another 500ml Erlenmeyer add 210ml
Alclorite (or other ~3.5% NaOCl solution, 215ml is 0.1mol) and cool this to +5°C or cooler. Then add 8.0g (0.2mol) NaOH to the now cold Alclorite
solution, by precooling it we prevent the temperature from getting too high. Cool the NaOH/Alclorite solution to -10°C in the freezer (If you check
the pH of the Alclorite you will find it to be 12-13, but this doesn't mean that I contains much NaOH from the beginning, a 0.05% solution has pH 12).
Grind 15.0g (0.1mol) phthalimide to a very, very fine powder. Now add this to the cold (-10°C) Alclorite solution, plug the flask and mix with
magstirrer on fastest setting (or shake). The phthalimide will dissolve within 5 min and the solution will not be more colored than before. Place in
the freezer again for at least 30 minutes.
Now add the cold NaOH solution prepared above to the cold (not over +5°C) Alclorite solution, nothing happens. Let stand in room temperature until it
reaches 20°C. Now heat to 80-85°C over 10 minutes and hold there for at least two minutes but not more then five. The solution will be a little less
achromatic now, but only slightly. Cool in water to room temperature or preferable below so the awaiting hydrochloric acid addition will not heat it
up to much.
Transfer the solution to a 1000ml beaker, keep some (~20-30ml) in the Erlenmeyer flask. Stir at medium speed on a magstirrer. Now begin to add
hydrochloric acid, the ~30% OTC version will do more then fine. You can probably add the first 25ml rather careless. But now you must measure pH, by
adding acid drop by drop and using the saved solution (the 20-30ml above) as backup you should eventually have a nice pH 7.0 solution (if you mess
this up, a pH above 7.0 is MUCH better then getting it below 7.0). The solution will become a little more colored when you add the hydrochloride acid.
At this point your solution has probably become cloudy because of a precipitate, this must be unreacted phthalimide (about 2g) so filter (suction!)
and save it. Now you will have a clear solution again.
Again add your solution to a 1000ml beaker, make sure the temperature is about +20°C or below. Strirr at medium speed and begin to slowly add glacial
acetic acid. If foaming has not begun after the two first milliliters, you probably should have neutralized better above, but just keep adding acid. A
lot of CO2 is formed so add it slowly. 15ml will probably be enough, but some extra milliliters will do no harm. The antharanilic acid will
precipitate, as you add the GAA.
Filter (Buchner, plastic cover to such away solution) and dry the crystals in an oven at +50°C (higher temperature might darken the crystals) for
several hours. The resulting powder should be slightly yellow/brown but NOT much. The yield at this point would probably be over 9g. Recrystallisation
from water with some decolorizing carbon present will give nice clean crystals.
After some runs you can grind up the saved phthalimide and reflux it in water (10-15ml/g, it will not dissolve) for half an hour, then cool and filter
to get pure phthalimide ready to be reused.
Contrast between this and the isatoic anhydride synthesis. The isatoic anhydride synthesis lacks the same extremes in temperature, going from about
5-10C to 25-30C. The differences are subtle but the reaction products are very clearly different.
He who fights with monsters should be careful lest he thereby become a monster. And if thou gaze long into an abyss, the abyss will also gaze into
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byko3y
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The procedure you posted is not working well. This is a copy paste of the procedure from rhodium's page you can find by googling, and the link is
already posted here, and it is in fact an adotation of vogel's procedure, which, in turn, can't be reproduced by some people. So don't mislead people
- you don't know what you talk about.
And actually I answered the question about the difference of the procedures in this thread and the one dedicated to isatoic anhydride ( http://www.sciencemadness.org/talk/viewthread.php?tid=33344 )
Also some of the patents mentioned in the thread contains research about the yield of byproduct - which is anthranilic acid, while the desired product
is isatoic anhydride. And it's all about hydrolysis, as I said.
[Edited on 22-4-2015 by byko3y]
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| Quote: Originally posted by byko3y | The procedure you posted is not working well. This is a copy paste of the procedure from rhodium's page you can find by googling, and the link is
already posted here, and it is in fact an adotation of vogel's procedure, which, in turn, can't be reproduced by some people. So don't mislead people
- you don't know what you talk about.
And actually I answered the question about the difference of the procedures in this thread and the one dedicated to isatoic anhydride ( http://www.sciencemadness.org/talk/viewthread.php?tid=33344 )
Also some of the patents mentioned in the thread contains research about the yield of byproduct - which is anthranilic acid, while the desired product
is isatoic anhydride. And it's all about hydrolysis, as I said.
[Edited on 22-4-2015 by byko3y] |
I havent had time to read fully through the patents, but if anthranilic acid is the byproduct and not phthalic acid or phthalimide salts, then a
melting point test should readily determine whether or not you have a product of mainly isatoic anhydride.
Anthranilic acid HCl melts at 168C or so, and zwitterion anthranilic acid at 146C or so. These would produce significant depressions in purity if
present at levels more than 10% I would say.
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thee.
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byko3y
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Recrystallization report
Finally performed purification of the anthranilic acid I prepared in my previous report.
Attempt to sublime the crude product at atmpspheric pressure led to melting into tan oil and distilling an aniline from it (aniline detected by odor
and by Na2Cr2O7+H2SO4 oxidation into aniline black). Maybe the pure anthranilic acid was dissolved in the aniline, but their separation gonna be a
pain.
You might have already known that the anthranilic acid is susceptible to decarboxylation on heating above melting point - this is why I've got the
aniline.
Rate of decarboxylation of the anthranilic acid after heating for 1 hour (decomposition rate is almost constant for the first hour), data from "The
Decarboxylation of Anthranilic Acid" - Stevens, Pepper, Lounsbury, which in its turn quotes data from Pawlewsbkri., Ber. 37: 592. 1904 :
150°C - 24%
160°C - 48%
190°C - 88%
200°C - 96%
So, heating at 200°C for 5 minutes leads to ~10% decomposition.
However, there's a much, much easier way to purify the anthranilic acid, which is crystallization from water. I was not able to obtain its solubility
at 100°C, but I could say by my observations it's somewhere at 30...100 g/L.
I suspended 1.78 g in 30 ml of water. Something like half of my crude product refused to dissolve even after boiling, so I needed to filter it (fast
filtration through a preheated funnel-paper filter). In the end I've got a clear maroon-colored solution (at almost 100°C).
While cooling to 5°C, nice long needles of anthranilic acid apeared all over the solution and the solution lost half of it's color.
After filtering and drying, 0.73 g of tan-colored crystal were obtained. As you can see, those are most likely 99% pure.
Less than half of the crude product made it through the crystallization, so I'd say the original product had 50% content of anthranilic acid. However,
I lost a decent amount of anthranilic acid due to insufficient amount of acetic acid (see my previuos report for details) and failure to process a
copper anthranilate precipitate. The former could lead to isatoic anhydride formation.
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byko3y
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Small update:
Totally (after few trials) I've got 2.8 g of a pure anthranilic acid from 4.5 g of crude product, and the yield could be even higher (up to 80-90%).
First time I did some mistakes, such as not heating the solution strong enough (80°C instead of at least 95).
You can detect the undissolved anthranilic acid by its color - it is tan colored, while everything else is either black or white.
After I have filtered off the hot solution, I got only black tar and almost invisible white crystals left on the filtering paper. This is what it
should look like.
If the residue contains peru-tan crystals - you either used not enough water, or your solution is too cold.
After cooling and filtering off precipitated crystals, mother liquor containg a decent amount of anthranilic acid (you can judge by it's maroon
color), so I carefully evaporated it until 1/4 of the original volume left, and then precipitated the crystals again (gives amount like 1/4-1/2 of the
first crop).
Also, I'd like to mention that the solubility of anthranilic acid rises sharply near the water boiling point, but it's really hard to filter the
solution and keep it 100°C so there's no strick proportions of crude product to water. I have a data about 450g/L solubility at 100°C, but I failed
to reach these numbers.
The data all over the internet says the anthranilic acid has white color - I doubt it's true. From some specific point of view some crystalls might
look white, but mostly they have a definite tan color.
[Edited on 7-5-2015 by byko3y]
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DraconicAcid
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My anthranilic acid is beige-yellow, without a trace of maroon.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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byko3y
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Edited the previuos post - mine were not maroon either, it was less reddish, peru-tan describes it better. But they were not beige-yellow for sure.
UPD once again: do you have crystals or a fine powder?
[Edited on 6-5-2015 by byko3y]
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Zephyr
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I also recently synthesized anthanilic acid, and like byko3y's, it is a light tan powder. I used nilered's procedure and double the amount. The yield
was 2.45g but I plan on recrystallizing.
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byko3y
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Nile Red follows rhodium's procedure, and once again - he forgets the importance of complete hydrolysis of phthalimide. Well, I don't think he even
knows it.
Anyway, he got the same powder I've got. Light-tan-peru powdery powder.
Pinkhippo11, what was the amount of phthalimide you used, so we can judge about yields.
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Zephyr
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Like I said, twice NileRed's amounts, so 5.16g, which leads to a yield of 51%.
However, I probably could have gotten higher if I had fully acidified it.
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byko3y
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51% is a relatively low yield. If Nile Red got even lower, than we can clearly see, that unmodified RHODIUM'S PROCEDURE just is NOT WORKING (mix NaOCl
with NaOH, then add phthalimide, add more NaOH, heat, etc...). I want to emphasize that, because over and over people recommend it.
Forgot to link the post in this thread with a good procedure and yields http://www.sciencemadness.org/talk/viewthread.php?tid=10272&... (first one)
[Edited on 7-5-2015 by byko3y]
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byko3y
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Finally measured the melting point of my product - it is 145+-3°C (at 141°C it is definitely solid, at 148°C it is definitely liquid). Sorry, don't
have appropriate devices to measure 0.1°C precise, and this stuff starts to decompose at its melting point to aniline, thus lowering the melting
point. At least it looks like anthraniic acid and not some chlorinated deriative.
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There is also methyl anthranilate or o toluidine to start the synthesis from.. the route involving o toluidine and permanganate makes an annoying
brown manganese sludge, but this is cleanly removed through filtration over celite...
I think the methyl anthranilatr hydrolysis route is very interesting, but i have not managed to precipitate solid anthranilic acid from it in the
zwitterionic form, even at the isoelectric point of pH 3.5... The toluidine route may not be so feasible but the ester route should and wont be as
watched.
Maybe its even possible to acetylate the ester as is using AA and DMAP if required as someone suggested.
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ChemPlayer_
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I'm getting a yield of anthranilic acid from the hypochlorite (bleach) Hofmann reaction with phthalimide between 44% (worst case) and 60% (first time
was luckiest!). The product is a light tan cream coloured powder which darkens slightly when re-crystallised.
I use the method of dissolving the phthalimide in the NaOH first, then adding the hypochlorite solution (I use 8.25%).
I suspect that the quality of sodium hypochlorite bleach from bottle to bottle (bearing in variations in batch / expiry date storage temperature and
ambient conditions in the supply chain) can be quite variable in practise, and this may lead to concentration differences. I haven't yet tried
titrating the bleach first to test this but I will start doing this on the next run.
Video of the detailed process: https://www.youtube.com/watch?v=DIadKyVKJAc
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byko3y
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At least 1.5 g of your product is dissolved in the water you've filtered. The color of the water tells about how much anthranilic acid (AA) it
contains. AA may be more soluble in an acidic solution than in a neutral one (although I don't know).
Freshly prepared concentrated hypochlorite/hypobromite works the best.
Also, I have no idea about exact impact of excess of hypochlorite on product. AFAIK, aniline on reaction with hypochlorite gives some polymerization
product, right? It might give some cyclization product with anthranilic acid.
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ChemPlayer_
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Thanks - that's very helpful info. I'd been assuming it was the isocyanate intermediate which was potentially prone to being over-oxidised by excess
hypochlorite, but thinking harder about it I guess that once this intermediate is formed ultimately the amine is the only likely end product of
hydrolysis or anything else that could happen.
It may be that getting the anthranilic acid out of solution could simply be the hardest part of this; it would explain 'beginners luck' because I was
certainly over-cautious with neutralisation the first time I did this!
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byko3y
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I have an idea to boil out the excess of water after AA filtration to obtain more AA precipitate without NaCl precipitating (to avoid tricky copper
extraction procedure), something like 80 ml of resulting solution per 15 g of total theoretic AA in the reaction. Of course, I'm talking about the
case of low concentration NaOCl solution used, which is quiet common because it is mostly sold dilluted, the highest one I was able to obtain is 6%.
Well, actually for most cases you will get more than 80 ml of solution when making 15 g of AA.
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CuReUS
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what about hitting phthallic acid with one mole of HN3(NaN3+H2SO4).I know azides are dangerous,but they
are cheap and the reaction is clean
[Edited on 23-6-2015 by CuReUS]
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Metacelsus
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Recovery of anthranilic acid from copper anthranilate?
I've followed byko3y's adaptation of the US patent procedure 2653971, and got a decent yield of presumed anthranilic acid (tan powder, not fully dry
yet so I don't have a mass). However, I was able to precipitate more as copper anthranilate. How do I get it back to anthranilic acid (S.C. Wack's
post mentioned hydrogen sulfide, but I don't want to deal with that.)
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