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woelen
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TCCA, Na-DCCA and cyanuric acid
Last week I purchased 1 kilo of almost 100% pure trichloroisocyanuric acid (TCCA) and 1 kilo of almost 100% pure sodium dichlorocyanuric acid
(Na-DCCA, a.k.a. sodium dichloroisocyanurate). Both of these are used as "stabilized chlorine" for outdoor swimming pools. In the Netherlands, both
chemicals can be purchased in the pure state without any additives like NaHCO3 or Na2CO3 as "Pool power Choc" (Na-DCCA, granulate) and "Pool
power Mini" (TCCA, tablets 20 grams). Probably this "Pool power" brand also is available in other countries.
These chemicals are quite interesting and can be used for generating chlorine gas in large quantities at fairly low price (between EUR 15 and EUR 20
per kilo, when purchased in 1 kilo quantities, much cheaper per kilo, when purchased in packs of 10 kilo).
Here, on sciencemadness, there is info about these chemicals, scattered over many different threads, but I think that these are so interesting that a
special thread could be devoted to them.
I intend to use them for making chlorine gas, but a lot of other interesting things can be done with them. When I add hydrochloric acid to these
chemicals, then Cl2 is produced, but a sludge of white cyanuric acid remains. When the sludge is boiled and all chlorine is driven off, then one can
slowly add small quantities of distilled water to the hot liquid, until all solid cyanuric acid dissolves. On cooling down, lots of featherlike
crystals of cyanuric acid are formed, which are easily dried and are absolutely free of smell of chlorine or swimmingpool-water.
I wonder, what interesting things can be done with the cyanuric acid, which remains. It is so easy to purify this, it seems like a waste to simply
throw this away.
Na-DCCA dissolves in water very well, TCCA does not dissolve in water (or only very slightly). TCCA, however, dissolves in acetone very well and on
evaporation, a mint-like smell remains! Is this due to formation of chlorbutol?
TCCA also does not dissolve in a solution of NaOH. It gives a white slurry. This surprises me. I expected to get a clear solution, with NaOCl and
trisodium cyanurate in solution.
As you can read, I already did some experimenting with these chemicals (which I now have just a few days), but I would like to have suggestions from
other members. Any ideas, but also any interesting facts about these chemicals are very welcome. I really think that these chems are interesting
enough to justify a thread, devoted to them.
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solo
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The TCICA Test for Distinguishing Primary and Secondary Alcohols
Gene A. Hiegel and Afshin K. Chaharmohal
J. Chem. Educ. 1997 74 423.
Abstract
Simple primary and secondary alcohols can easily be distinguished by their rate of oxidation with trichloroisocyanuric acid (TCICA).1,2 The TCICA test
is conducted by adding the unknown to a solution of TCICA in acetonitrile3 containing hydrochloric acid4 and measuring the time for a precipitate5 to
form. Primary alcohols react slowly and secondary alcohols react rapidly. To generate comparison data for primary and secondary alcohols, tests should
be first carried out using ethanol and 2-propanol.6
TCICA Test Procedure
To a small test tube add 0.5 mL of the TCICA solution in acetonitrile (30 mg/mL), one drop of 1 N HCl, and one drop of the sample. After noting the
time, flick the test tube with your finger several times to mix the contents. Watch the test tube until a precipitate forms and record the elapsed
time. The elapsed time could range from a few seconds to a few minutes.
In order to destroy any unreacted TCICA before disposal in the appropriate waste container, a few crystals of sodium hydrogen sulfite (NaHSO3) and a
few drops of water should be added to the test tube, and the mixture should be allowed to react for a few minutes.7
Caution: TCICA solution is a bleach and a strong oxidizing agent and will discolor clothes. Do not get the solution on your clothes,
your skin, or any lab surfaces. Spills can be cleaned up with sodium hydroxide sulfite solution.
Notes
1. Trichloroisocyanuric acid can be used to prepare ketones from secondary alcohols; see Hiegel, G. A.; Nalbandy, M. Synth. Commun. 1992, 22, 1589.
2. Other methods for distinguishing alcohols include the Lucas testsee Roberts, R. M.; Gilbert, J. C.; Martin, S. F. Experimental Organic Chemistry;
Saunders: New York, 1994; p 693; and 1H NMR see McGreer, D. E.; Mocek, M. M. J. Chem. Educ. 1963, 40, 358.
3. As other strong oxidizing agents, TCICA should be added to the solvent, not the solvent to the TCICA. Solutions of
TCICA in acetonitrile are stable for years when stored in a brown bottle. TCICA is used as a swimming pool disinfectant and is widely available.
4. The reaction will proceed without the HCl, but the reaction times are more reliable when it is used.
5. The precipitate is cyanuric acid, a solid used to inhibit light-induced destruction of chlorine in swimming pools.
6. We have used this test in organic lab classes for several years, and it gives reliable results in the hands of students. Students are not provided
with comparison reactions times; therefore, each student runs the ethanol and 2-propanol tests to get this information. Primary alcohols take about
7-30 min to give a precipitate and secondary alcohols take about 0.1-1.2 min. Tertiary alcohols, which cannot be oxidized directly, take 3 or more
hours before a precipitate begins to form; presumably this occurs after dehydration to an alkene.
7. Iodide-starch test paper wetted with water can be used to test for the presence of oxidizing power before the solution is placed in the waste
container
Attachment: The TCICA test for distinguishing primary and secondary alcohols.pdf (86kB)
This file has been downloaded 6691 times
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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Chris The Great
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I tried adding TCCA to NaOH, or NaHCO3, and just got lots of clear, irritating and stinky gas. No clue as to what the reaction was. Anyone else have
a clue? I was just expecting the same as woelen.
Interesting test there solo, easy except for needing acetonitrile.
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praseodym
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TCCA releases hypochlorous acid on contact with water. TCCA froms an explosive product with cyanuric acid + sodium hydroxide. Nitrogen trichloride, a
highly explosive compound, may from if TCCA contacts ammonia, ammonia salts, urea, or similar nitrogen - containing compounds. This material is a
powerful oxidizer and therefore, a potentially violent reaction with combustible materials may occur. Furthermore, an interesting property of TCCA is
the chemiluminescence produced during their reaction with luminol in alkaline medium. 
Alles sollte so einfach wie möglich gemacht werden aber nicht einfacher.
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woelen
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| Quote: | Originally posted by Chris The Great
I tried adding TCCA to NaOH, or NaHCO3, and just got lots of clear, irritating and stinky gas. No clue as to what the reaction was. Anyone else have
a clue? I was just expecting the same as woelen. |
Is your TCCA pure? I did the test another time and checked the presence of gas.
I only get a white slurry, no gas at all. The liquid alsmost remains odourless, just a faint smell of TCCA (typical swimming pool odour).
What happens if you add dilute sulphuric acid to your TCCA? No gas should be formed and the solid should not dissolve. If a colorless gas is formed,
then the TCCA is not pure and contains "enhancers".
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woelen
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I did another set of experiments and did much more careful observations:
1) Add solid TCCA to a concentrated solution of NaOH: The solid breaks down fairly quickly. The liquid becomes turbid and light green. A very small
amount of gas is formed, but not very much. Enough, however, to be observed easily. To my opinion, the gas is odourless. I could smell some typical
swimmingpool odour, albeit weak, but this odour also is produced by the liquid, when there are no bubbles.
2) Add solid Na-DCCA to a concentrated solution of NaOH: Almost the same kind of observation as with solid TCCA.
3) Add a solution of Na-DCCA in water to a warm concentrated solution of NaOH: When the two liquids are mixed, then the liquid becomes very light
green instead of colorless, also tiny bubbles are formed, but this is very minor.
I explain the observations as follows. This is not established chemistry, it is my own theory.
Both TCCA and Na-DCCA react with NaOH to form hypochlorite and sodium cyanurate. The latter is soluble in water, but in very concentrated NaOH it is
less soluble. The green color is due to the formation of the hypochlorite. Hypochlorite ion is very pale green/yellow in solution, due to an
equilibrium with the very weak acid HOCl, which is light yellow/green.
with TCCA: 6OH(-) + C3N3O3Cl3 ---> C3N3O3(3-) + 3ClO(-) + 3H2O
with Na-DCCA: 4OH(-) + C3N3O3Cl2(-) --> C3N3O3(3-) + 2ClO(-) + 2H2O
The Na(+) ions are just spectator ions.
At high Na(+) concentration, however, the C3N3O3(3-) ion (cyanurate) gives a precipitate of Na3C3N3O3.
The very weak evolution of gas probably is due to decomposition of ClO(-)/HOCl. At very high concentrated (e.g. near the solid TCCA or Na-DCCA in
conc. NaOH-solution) a small part decomposes. Also, when the liquid is warm, some of the hypochlorite may decompose. Hypochlorite in solution is quite
unstable, when its concentration goes beyond 15 ... 20 % active chlorine.
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Polverone
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| Quote: | | Originally posted by praseodymFurthermore, an interesting property of TCCA is the chemiluminescence produced during their reaction with
luminol in alkaline medium. |
Another nice chemiluminescent reaction is the one between TCCA and hydrogen peroxide. It gives the red glow of singlet oxygen like the interaction
between metal hypochlorites and peroxide, but TCCA offers more concentrated available chlorine (and thus more visible light) than commonly available
hypochlorites.
Cyanuric acid has been very useful to me in preparing cynates/cyanurates and subsequently cyanides by high-temperature reduction, but that is less
useful if you have a ready commercial supply of cyanides.
I believe that cynauric acid can be used as an in-situ source of cyanic acid for ester formation in high-BP alcohols. It will certainly disappear
after boiling in glycerol, presumably due to ester formation.
TCCA forms a lovely purple copper salt. I've never seen any other purple copper compound.
TCCA will rapidly vanish, bubbling and emitting visible vapors, in a solution of aqueous ammonia. If it weren't for the lachrymatory vapor or gas
emitted it would be a neat stage trick, almost like dry ice but shorter-lasting.
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Organikum
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TCCA may be named as you wish "green" or watever. It will make you cry.
Trust me on this.
/ORG
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woelen
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| Quote: | Originally posted by Polverone
Another nice chemiluminescent reaction is the one between TCCA and hydrogen peroxide. It gives the red glow of singlet oxygen like the interaction
between metal hypochlorites and peroxide, but TCCA offers more concentrated available chlorine (and thus more visible light) than commonly available
hypochlorites. |
This indeed is a very nice experiment. With TCCA, however, the result is disappointing. I can hardly see any red glow. With Na-DCCA, the result,
however, is lovely. That is the best chemiluminiscence experiment I've ever seen, besides the well-known luminol experiment. Probably Na-DCCA works
better, because it dissolves easily in water, while TCCA is almost insoluble. Na-DCCA also still has over 60% available chlorine.
I also did this experiment by adding solid Ca(ClO)2 to 30% H2O2. This also gives a nice result, but with Na-DCCA the reaction is longer lasting. You
have a nice glow for a longer time, while with Ca(ClO)2 there is a red glow for a fraction of a second, accompanied with a very violent reaction.
| Quote: | Cyanuric acid has been very useful to me in preparing cynates/cyanurates and subsequently cyanides by high-temperature reduction, but that is less
useful if you have a ready commercial supply of cyanides.
I believe that cynauric acid can be used as an in-situ source of cyanic acid for ester formation in high-BP alcohols. It will certainly disappear
after boiling in glycerol, presumably due to ester formation.
TCCA forms a lovely purple copper salt. I've never seen any other purple copper compound.
TCCA will rapidly vanish, bubbling and emitting visible vapors, in a solution of aqueous ammonia. If it weren't for the lachrymatory vapor or gas
emitted it would be a neat stage trick, almost like dry ice but shorter-lasting. |
A lot of interesting suggestions. Like the chemiluminiscence experiment, they sound interesting. I'll try them. Especially the purple copper salt
sounds interesting. Is this simply prepared by adding a solution of copper sulfate to TCCA? Is it possible to isolate this salt? If you have a
"recipe" for this, that would be nice.
In the meantime I also found a source for pure cyanuric acid (outdoor swimming pool stabilizer for hypochlorite based chlorine) for EUR 15 or so per
kilo. Can this easily be depolymerized, making cyanic acid and cyanates? I also was thinking of making cyanogen chloride. Could a reaction of HCl
(dry, made by adding NaCl to H2SO4) and cyanuric acid give cyanuric chloride (not to be confused with TCCA, it lacks the O's), which in turn can be
converted to cyanogen chloride. This would open up a source of cyanide, without the need to use red heat on a mix of carbon and cyanates or
cyanurates.
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Polverone
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| Quote: | | A lot of interesting suggestions. Like the chemiluminiscence experiment, they sound interesting. I'll try them. Especially the purple copper salt
sounds interesting. Is this simply prepared by adding a solution of copper sulfate to TCCA? Is it possible to isolate this salt? If you have a
"recipe" for this, that would be nice. |
It actually seems to work better with the sodium salt rather than the pure acid. This may be due to pH effects or to poor aqueous solubility of TCCA.
When I observed it before it was incidental to what I was doing so I didn't observe too closely. Just now I have tried again and I think I can say
how: grind together TCCA and CuSO4 in a mortar, add a bit of water, and grind in sodium carbonate. The mixture will turn purple. This isn't how I
originally observed it, and I think the color was stronger when I saw it before, but as I said I was not focusing on the purple compound at the time.
Perhaps I should have paid more attention to it because whatever I was doing at the time did not pan out, while the memory of the purple compound
stuck with me.
While trying to remember how to get the color just now, I found another interesting reaction. Grind together NaOH and CuSO4 with a bit of water so you
have a strongly alkaline solution containing freshly precipitated CuO. Grind in TCCA and the black color changes to a rich reddish brown. Dilute with
water and the mixture bubbles, reverting to black. I don't know if the decomposition on dilution was strictly from dilution; it could also be from the
heat of NaOH dilution.
| Quote: | | In the meantime I also found a source for pure cyanuric acid (outdoor swimming pool stabilizer for hypochlorite based chlorine) for EUR 15 or so per
kilo. Can this easily be depolymerized, making cyanic acid and cyanates? I also was thinking of making cyanogen chloride. Could a reaction of HCl
(dry, made by adding NaCl to H2SO4) and cyanuric acid give cyanuric chloride (not to be confused with TCCA, it lacks the O's), which in turn can be
converted to cyanogen chloride. This would open up a source of cyanide, without the need to use red heat on a mix of carbon and cyanates or
cyanurates. |
Metal cyanates (or at least sodium cyanate) can be made by heating an intimately powdered mixture of metal carbonate with cynauric acid, or so an old
British patent told me. I never stopped heating early enough to try to isolate cyanates, as I was always interested in cyanides.
You can have some real fun with copper carbonate and cyanuric acid. Cyanic or cyanuric acid appears to form a bit more reddish purple compound with
copper (oops, I guess I've actually seen maybe two sources of purple copper compounds, though quite similar if not indeed identical). You can see it
if you trickle a bit of copper carbonate down the side of a test tube, then drop some cyanuric acid to the bottom and heat it over a flame. As the
vapors come off they will react with copper carbonate clinging to the tube wall to form a purple compound like that near near the middle of the tube
in the photograph.
In the case of the above photograph, I actually had excess copper carbonate powder sitting atop my initial load of cyanuric acid. I had thought it
would be a good way to react more cyanic/cyanuric acid with copper carbonate before the vapors condensed again. But as I heated it, I saw no purple
compounds in the bulk at the bottom of the tube, though there was evidently a reaction. Some acid vapors still escaped to react further up the tube as
can be seen in the photograph. While I was continuing the strong heating, there was suddenly a little sizzling noise and a brief orange glow from the
bottom of the tube in an area about the size of one of the original cyanuric acid grains. As I continued heating and rotating the tube there were a
few more of these surprisingly vigorous reactions. Each one left behind metallic copper. I was only using the flame of an alcohol burner, and never
expected copper carbonate/oxide to act in an almost pyrotechnic manner with cyanuric acid.
Nearer to the end of the tube there is a small dark blue patch, though the color may be difficult to see in the picture. It looks like ammonia-copper
complex, and it's quite possible that cyanuric acid side reactions gave off ammonia.
Cyanuric acid goes to vapor easily but recondenses to solid easily as well. I don't know what would be necessary if you wanted to try to isolate
liquid cyanic acid from it, even briefly.
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garage chemist
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The observation that TCCA dissolves in dilute NaOH solution made me repeat my experiment for the synthesis of chloroform from TCCA which didn't work
when I last did it.
1,3g NaOH (0,03 mol + 0,1g excess) were dissolved in 30ml water and the solution cooled down with a cold water bath.
2,5g 92% TCCA (0,01 mol) were finely powdered with mortar and pestle (important!) and added to the NaOH solution under stirring.
Nearly everything dissolved, to yield a slightly green/yellow solution. It was decanted from undissolved material, cooled down again, poured into a
50ml ground- glass flask, a stirbar was added and it was stirred at medium speed.
A half pipette (ca. 1ml) of acetone was added and immediately a small vigreux column put on the flask, to serve as a reflux condenser so that no
evaporation losses occured.
After about 30 seconds, the reaction suddenly kicked in, evident by it becoming suddenly cloudy and very warm.
The stirrer was switched off and slowly a blob of chloroform deposited at the bottom. 
It works! One can make chloroform directly from TCCA, without using huge amounts of bleach!
I'm gonna run this reaction with twenty times those amounts, isolate the chloroform by distillation directly from the reaction mix and write an
article in prepublication about it.
EDIT: I realize that I used only half of the necessary amount of NaOH. That may explain the low yield: it was far less than half a milliliter of
chloroform.
[Edited on 26-4-2006 by garage chemist]
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woelen
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@polverone: I tried to make the purple compound and it works like a charm. What I did is dissolving the sodium salt Na-DCCA and add an excess amount
of a solution of copper sulfate. When this is done, then a heavy precipitate with a very bright purple color is produced, which can easily be
isolated. I rinsed the precipitate with water and now it is drying. The color really is very neat.
I also did the experiment of mixing basic copper carbonate with cyanuric acid. The cyanuric acid was made from Na-DCCA, to which excess dilute HCl was
added and from which all chlorine was driven away by heating. On cooling down feather-like crystals were formed and the dried crystals I mixed with
the copper carbonate. I, however, could not reproduce your nice results. I obtained a black powder on heating and at the colder parts of the test tube
I obtained a white solid (evaporated cyanuric acid and resublimed again I suppose). I did not obtain all the reds, browns, purples and blues. Just
black  . The black stuff probably just is plain CuO. I also did not observe any of
the 'pyrotechnic' reactions, although at a certain point I even heated the stuff with a propane torch.
I certainly will continue experimenting with copper / cyanuric acid / Na-DCCA or TCCA. If I obtain interesting results, then I'll certainly publish
them on my website. A picture of the nice purple compound will be posted anyway, when it is dry.
----------------------------------------------------------------------------------------------------
@garage chemist: That is a great job you did. I read the recent thread about TCCA and CHCl3 on versuchschemie.de and also the thread on sciencemadness
with great interest, but it is even better that you actually succeeded in making CHCl3 as a separate liquid now from this compound. If you have
optimized your preparation, then I certainly would like to see your article about that.
The TCCA you have, is it 92% TCCA or 92% active chlorine? I am inclined to think the latter, the number is too much of a coincidence: 100% TCCA has an
active chlorine content of almost 92%.
My bottle tells that it has a minimum active chlorine content of 90%, so my TCCA probably is pure or almost pure. I did tests with H2SO4 and then I do
not get any bubbles, and that is a good sign, so there are no carbonate fillers and the like.
My bottle of Na-DCCA tells me that it contains 100% sodium dichloroisocyanuric acid, and that on practical application at least 60% active chlorine is
available in this compound. The theoretical active chlorine of Na-DCCA is 64%.
[Edited on 26-4-06 by woelen]
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garage chemist
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The bottle says that it is 92% pure TCCA, this number is not the active chlorine content. However, it doesn't contain any carbonate fillers: no
reaction with dilute H2SO4.
First I bought the wrong tablets, and they contained about 20% sodium carbonate (I downloaded their safety data sheet).
The tablets with carbonate fillers are sold as "fast- dissolving", while the ones made of nearly pure TCCA are sold as "slow- dissolving".
I am not sure if the reaction of TCCA with NaOH solution goes to completion, due to one reason: TCCA is industrially manufactured by adding chlorine
to an aqueous solution of cyanuric acid in NaOH solution.
This means that the opposite reaction hypochlorite + cyanuric acid ---> TCCA also occurs readily.
There seems to be an equilibrium. However, the fact that some chloroform was produced in my experiment shows that some hypochlorite is present.
However, the yield was low.
I have the suspicion that yields won't improve much by using the correct amount of NaOH (2,4g NaOH + 2,5g 92% TCCA).
Maybe only one chlorine atom of ther TCCA reacts, giving one mol of hypochlorite per mol of TCCA and Na-DCCA as byproduct.
I don't have Na-DCCA. It would be nice if you could try that out for me: 1 mol Na-DCCA, 4 mol NaOH, lots of water, some acetone, and see if there is
chloroform being produced.
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woelen
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Garage chemist, right now, woelen is going in horizontal position  (it is over
23:00 over here), but tomorrow evening I will try the experiment with Na-DCCA, NaOH and acetone and see what happens. I'll keep you updated with the
result.
[Edited on 26-4-06 by woelen]
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woelen
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Well, now it is time to do the experiment. I wonder, however, how you come to the ratio of 1 mole of Na-DCCA and 4 moles of NaOH. I find the following
equation for the net reaction:
2CH3COCH3 + 3NaC3N3O3Cl2 + 8NaOH --> 2CH3COONa + 2CHCl3 + 3Na3C3N3O3 + 6H2O
For 1 gram of Na-DCCA, 0.4849 grams of NaOH and 0.176 grams of acetone are needed. If there is 100% yield, then I expect 0.3618 grams of CHCl3.
I'll perform the experiment in a long thin tube, if any CHCl3 settles, then I can see how many uL are formed.
Nevertheless, I'll also do the experiment with a 1 : 4 molar ratio of Na-DCCA and NaOH and see which works best. That means 0.72 grams of NaOH.
EDIT: results of experiments
First, I want to mention that all weights are +/- 0.01 gram.
I prepared three liquids:
A: 1 gram of Na-DCCA and 0.5 gram of NaOH, dissolved such that the total volume of the liquid is just below 20 ml.
B: 1 gram of Na-DCCA and 0.75 gram of NaOH, dissolved such that the total volume of the liquid is just below 20 ml.
C: 0.6 gram of aceton, mixed with 2.5 grams of water.
Liquids A and B both are clear and light green liquids. This is the maximum concentration I could achieve without the liquids being cloudy. I prepared
them as follows:
Dissolve 1 gram of Na-DCCA in just over 10 ml of water. This results in an almost colorless and clear liquid. Do this two times, once for liquid A and
once for liquid B.
Dissolve 0.5 gram of NaOH in a small volume of water and add all to one of the solutions of Na-DCCA. This results in formation of a white cloud in the
liquid. Next, add water slowly, until the cloudiness just disappears. That works very well. The volume then is almost 20 ml. A similar result is
obtained for liquid B, that also must be diluted to almost 20 ml before it becomes clear again.
Next, I did the experiments:
Add 1/3 of liquid C to liquid A and quickly stopper. The clear liquid becomes cloudy very quickly and considerable heat is produced.
Add another 1/3 of liquid C to liquid B. This has the same result as with liquid A.
Leave both cloudy liquids alone for 1 hour, while they are in a cool waterbath. After 1 hour, both liquids are still somewhat cloudy, but not as much
as when the experiment started. There is a blob of chloroform at the bottom of the tube. There is no noticeably difference in yield for both
experiments. My tube only allows measuring at 0.05 ml resolution and I could not read off easily. I estimate the volume of the blob to be appr. 0.05
ml. The yield is not very good. I expected around 0.2 ml of chloroform, so I only obtained 1/4 of what I expected.
As a final test, I checked whether all Na-DCCA is used up with 1/3 of liquid C. So, to one of the liquids I added the last 1/3 of liquid C. This does
not result in heating up any more, so with 1/3 of liquid C I already had (slight) excess of acetone.
The blob definitely is chloroform, it had a nice sweet smell. Now, if we take into account the solubility of chloroform in water, then the yield is
much better. Solubility of chloroform is 0.8 grams per 100 ml of water. I had a volume of appr. 20 ml, this means that 0.16 grams can be dissolved in
that amount of water. If the blob indeed is around 0.05 ml, then there is another 0.075 grams of chloroform and the total yield then is 2.3 .. 2.4
grams. This is a yield of 2/3 of the theoretical amount, which seems fairly good.
Altogether, using Na-DCCA, chloroform can be obtained, but one has to put some effort in it to isolate it. Just collecting the liquid from the bottom
results in too many losses. The chloroform, dissolved in the water, also must be distilled in order to have acceptable yield. The limiting factor is
the fairly low solubility of the Na-DCCA/NaOH mix. Only 1 gram of Na-DCCA can be dissolved in almost 20 ml of water, to which quite some NaOH is
added.
===============================================================
I also did some other experiments with Na-DCCA (polverone's copper experiments and making cyanuric acid). Some pictures are added here of results. The
copper-salt looks really neat.
http://woelen.homescience.net/science/chem/exps/TCCA/index.h...
The color of the copper salt is really hard to capture. My digital camera has difficulties in reproducing the color precisely. What these pictures
show is a good approximation, but you really have to see the precipitate yourself in order to appreciate its remarkable color. For copper this color
is remarkable, because its normal color is in the greens, cyans and blues.
EDIT: fixed hyperlink, such that it works again.
[Edited on 12-8-12 by woelen]
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garage chemist
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Very good, woelen! Great results!
We have now reason to believe that all three chlorine atoms on TCCA can react with NaOH to produce hypochlorite and that this can undergo the haloform
reaction.
The reaction mix must be distilled in order to obtain the chloroform, that's understood.
One should distill until only water comes over.
The chloroform must also be washed with some more water in order to remove the acetone, which should be present in a slight excess.
I also re-did my experiment with 2,5g TCCA and 2,4g NaOH, total volume of liquid 35ml (this becomes clear, no insoluble matter).
An excess of acetone was added under stirring, it became so hot that the produced chloroform started to boil, but I had my reflux condenser on it so
no vapors escaped.
The blob of chloroform was distinctly larger this time.
I haven't measured yield, but it seems better than last time.
I don't have a means of mesauring small volumes, so the only real way to find out the yield is to run a large batch and distill the chloroform out of
the mix.
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garage chemist
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I have run the reaction with 24g NaOH (0,6 mol) and 25g 92% TCCA (0,1 mol) in 250ml water, and 7,2g acetone (0,124 mol).
I figured that the reaction would go as follows:
6 NaOH + C3N3O3Cl3 ----> 3 NaOCl + Na3C3N3O3 + 3 H2O
Then the haloform reaction:
3 NaOCl + CH3COCH3 -----> CH3COONa + CHCl3 + 2 NaOH
Maybe I should have used somewhat less NaOH, as I now see that the reaction produces NaOH itself. Also NaOH can hydrolyse chloroform when the two come
into prolonged contact, especially at elevated temperature.
Here the synthesis report:
The TCCA dissolved in the NaOH solution, however, it needed a few minutes of stirring. A small amount of foam was produced.
The acetone was diluted with two times its volume of water and put into a dropping funnel
The reaction was run in a three- neck 500ml round bottom flask with efficient reflux condenser.
The acetone solution was dropped in under violent stirring at a rate of about 3 drops per second.
It heated up rapidly, and soon started to boil. The rate of acetone addition was not decreased, but rather increased to bring the reaction to a finish
as soon as possible (in less than 5 minutes), since heat causes hypochlorites to decompose.
As the acetone was added completely, the mix was left to cool down. Some chloroform was seen settling down.
The flask was rigged up for distillation, and slowly distilled under magnetic stirring. A chloroform/water- azeotrope came over at about 55°C, and as
it stopped coming over the steam temperature actually went down until the residual solution started boiling. Then it quickly went to over 90°C, and
only water came over. I stopped the distillation at this point.
To the raw chloroform in the receiver was added an equal amount of water and it was swirled to remove residual acetone.
The crude chloroform was extracted with a pipette and weighed.
It weighed 6g, which is exactly 50% of theory. Strange.
The distillation residue in the flask had absolutely no smell of chloroform, so nothing remained in there.
The chloroform was washed with conc. H2SO4 to remove the rest of acetone (the H2SO4 becomes dark red/brown when acetone is present), it was only
discolored a slight bit.
I didn't post this in prepublication, because the yield is too low for this. The reaction will have to be optimised at first.
I can think of two explanations for the low yield:
first the high temperature in the synthesis could have caused half of the hypochlorite to decompose. Next time most of the reaction water will be
added as ice, to provide internal cooling because with external cooling the reaction would take too much time to finish.
Second, I used too much NaOH. Next time I will use only 4 mol per mol of TCCA, to take into account the 2 moles being produced in the haloform
reaction. This means that not all TCCA will dissolve when it is added to the NaOH solution.
A strange thing is that a white powder precipitated from the distillation residue, and it did so already while still boiling hot!
Cooling did NOT increase the amount of precipitate.
The liquid above it is also strongly alkaline, so it can't be cyanuric acid.
The residue was not present before distillation, when there was the chloroform.
[Edited on 1-5-2006 by garage chemist]
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woelen
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Did you isolate some of the white stuff, which was formed during distillation? This may me the key to explaining the low yield.
I'll see if I can reproduce that observation on a small scale. If that precipitate contains chlorine, then I can perfectly understand why the yield of
CHCl3 is so low.
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garage chemist
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I still have the distillation residue in the flask, unaltered.
The precipitate only formed as the solution was being heated to boiling after the chloroform had been distilled off (although some of it may have
formed during distillation of the chloroform, the mix was cluody the whole time).
I'll test the supernatant solution for chloride, with AgNO3 solution.
If there is really a lot of chloride in there, then it is clear that the chloroform has been hydrolysed by the excess of NaOH.
The reaction of chloroform with hot NaOH solution produces dichlorocarbene, an extremely reactive species which undergoes a large number of reactions.
It may have reacted with the sodium cyanurate, forming some strange new
compound.
That makes good sense: the fact that the precipitate occured during distillation, and that the precipitate does not change solubility with
temperature, e.g. is most likely insoluble, supports the theory that dichlorocarbene was produced from the excess NaOH and chloroform and reacted with
the cyanurate.
I'll filter the precipitate and see what properties this material has. An unknown compound!
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garage chemist
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I tested the liquid above the white stuff for chloride (added a few drops of it to some HNO3- acidified AgNO3 solution) and it was strongly positive
(thick white clouds of precipitate).
So either half of the hypochlorite disproportionated to chloride and chlorate (likely, as the solution was very hot during reaction) or half of the
chloroform was hydrolyzed by the excess NaOH.
Whatever it was, it is clear that I have to both
a) keep the solution cold during haloform reaction, and add the acetone very slowly so that this is possible, and
b) use the correct amount of NaOH: 4 mol per mol of TCCA.
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woelen
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| Quote: | | use the correct amount of NaOH: 4 mol per mol of TCCA |
That is an interesting conclusion. I already found in my equation for Na-DCCA that I did not need 4 mol of NaOH per mol of Na-DCCA, but only 8 mol of
NaOH per 3 mol of Na-DCCA. I derived the reaction equation at once, without the intermediate step of the hypochlorite. But, now we have explicit, what
it the problem. The haloform reaction produces NaOH again, as you already mentioned.
Maybe you should even use a little bit less NaOH, than the computed amount. Just a little bit, to be sure that the liquid does not become alkaline.
Also, having an excess of acetone may be a bad idea. I noticed that acetone and TCCA react with each other, giving a refreshing and cooling smell
(quite pleasant). I suspect that smell is due to formation of chlorobutanol. Chloroform and acetone also react with each other in the presence of an
alkali (which acts as catalyst) as follows:
CHCl3 + OH(-) --> H2O + CCl3(-)
CH3COCH3 + CCl3(-) --> CH3C(O-)(CCl3)CH3
The latter ion reacts with water, giving CH3C(OH)(CCl3)CH3 and OH(-). This is isobutanol, with all three H-atoms of one of the methyl groups replaced
by chlorine. A lovely very nice smelling compound, which makes you feel drowsy, but it is not what you want.
Next weekend, I am going to do some tests also with the correctly computed amounts of TCCA and NaOH. I already found out that TCCA does dissolve in
NaOH quite well, but it does so very slowly. However, with patience and grinding it does dissolve. The only problem I observe is that part of it
already decomposes while dissolving: formation of odourless and colorless gas, when the solid TCCA dissolves in NaOH-solution. Probably that gas is
oxygen, due to decomposition of the ClO(-) at that high concentration.
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garage chemist
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Formation of chlorobutanol is very possible, in the alkaline liquid, and with excess of acetone. But my solution doesn't smell like it (I know the
smell) and distillation would also get rid of it (it has a high boiling point).
With the stochiometry:
6 NaOH + C3N3O3Cl3 ----> 3 NaOCl + Na3C3N3O3 + 3 H2O
3 NaOCl + CH3COCH3 -----> CH3COONa + CHCl3 + 2 NaOH
We see that we can reduce the 6 mol NaOH to 4 mol, because 2 mol get produced later by the haloform reaction.
However, this means that the TCCA will not dissolve completely in the NaOH. I hope that this won't interfere with the reaction.
The chloroform will have to be fractionally distilled through a column after washing with conc. H2SO4, washing with water and drying with CaCl2 (this
is what the Organikum recommends for purification of chloroform).
The whole thing would be quite labor- intensive, and only be worthwhile if done on a large scale (at least 50g TCCA).
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Organikum
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TCCA chlorinates acetone nicely, if I am not mistaken this proceeds up to tri-chlorination provided that enough TCCA is present.
The reaction is highly exothermic and the mono, di and trichlorinated acetone derivates are lachrymators (monochloro and dichloro are for sure).
So if I am not mistaken a way to do this might be to add acetone slowly to an excess of TCCA and after this has reacted to completeness to add NaOH to
produce chloroform. One might even remove the precipitated cyanuric acid by letting it settle and decant the liquid - filtration is pretty futile -
thus minimizing the amount NaOH needed.
I hope my memory didn´t fool me with the way the haloform works....
/ORG
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woelen
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I did an experiment by adding some TCCA to acetone. It quickly dissolves and a clear and colorless liquid is obtained. There was, however, not a sign
of any reaction. I let the acetone evaporate and a white solid was obtained again. This solid had a smell like mint/refreshing, the typical smell of
chlorobutanol, but it was only very weak. Knowing that its smell is very strong, one can conclude that only a very small amount is converted. The
solid also unmistakenly had the standard smell of TCCA (swimmingpool odour), so most of it is not converted at all. As a final test, I added dilute
HCl to the white solid and it gives bubbles of chlorine and the turbid green/white liquid, typical of adding HCl to TCCA.
So, does the reaction between acetone and TCCA need a special initiation, or does it requitre heating to set off?
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Organikum
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The reaction of acetone with TCCA produces chloroacetones mono/di/ti depending on the amount of TCCA present. I posted a thread times ago about this
method for the production of monochlorocatone.
The reaction is strongly exothermic.
Be careful!
A small amount of HCl helps initiating the reaction without having to apply heat whats a bad idea as it will end in a runaway. You have to cool it.
Is your TCCA scented?
/ORG
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