Sciencemadness Discussion Board - Thermal decomposition products of TCCA in water at extraction from chlorinating tablets

Thermal decomposition products of TCCA in water at extraction from chlorinating tablets

bahamuth - 24-2-2012 at 05:06

Starting a new thread as I the info on this subject that I found on the forum was either scattered or just mentioned in passing.

The pool tablets I aquired have a sodium carbonate content of around 45% extrapolated from the MSDS which states >50% TCCA and the only other constituent being Na2CO3 in 25-50%.

First attempt was to dissolve these directly in warm water to try to dissolve the Na2CO3 leaving a residue of fairly pure TCCA, but this failed sort of as a vigerous reaction ensued the addition of the powdered pool chlorinating tablets to the hot water with stirring. The reaction was followed by total dissolution and a noxious gas formation in addition to giving the solutiuon a green tinge. The solution was abandoned as this was not the correct way.

Second attempt was to disolve the powdered tablets in acetone, which left atleast a majority of the Na2CO3 undissolved followed by filtering to remove said carbonate. The acetone/TCCA mixture was evaporated over a steam bath with removal from heat before totally dry to avoid any thermal decomposition, leaving a white solid with a green/yellow tinge.
This solid was attempted purified by dissolving in boiling water and recrystallize (wishful thinking I know but as 2 gram of TCCA dissolves in 1000 ml ambient water I expected a slightly higher amount to dissolve in boiling water facilitating a recrystallization). The TCCA/water solution was left to boil in a beaker covered with a watchglass to complete solvation and hinder excessive evaporation of the water.

This is where the "incident" occured. After some minutes of boiling the TCCA/water mix quite alot more of the TCCA seemed to go into solution so I decided I'll let it boil some more and finally filter it and recrystallize it. But, then a fairly loud "pop/boom" was heard and the ratteling of the watchglass as something must have detonated in the vapor phase of the mix. I immediatly removed the mix from the heat source and lifted off the watchglass to aid the escape of any explosive gases. A extremly noxious/lachrymatory gas was detected while I was colling the mixture by adding cold water from the tap (I just wanted to kill any thermal runaway if any).

So this begs the question, what formed that could decompose violently? I have some suggestions but I'll ask if anyone here has has a similar experience and/or suggestions first?

Could it be nitrogen trichloride...?

Also, if anyone have a working suggestion as to extract and purify TCCA from a Na2CO3 mix I would like you to share it.

weiming1998 - 24-2-2012 at 06:50

For the recrystallizing, maybe instead of heating, you can just leave the solution in a container under the sun until crystals form. That wouldn't make it explode. Maybe water catalyses the thermal decomposition of TCCA, like hot water(not even boiling), will make calcium hypochlorite decompose into oxygen and CaCl2, but all sources say that it decomposes at above 100 degrees celsius (Wikipedia says 175oC).

If it still doesn't work, then use something like dichloromethane or any highly chlorinated solvents to dissolve the TCCA. Then dissolve in water and evaporate in a wide container.

[Edited on 24-2-2012 by weiming1998]

AndersHoveland - 24-2-2012 at 07:07

Acetone should not be used, because it is vulnerable to oxidation/chlorination through its enol tautomer. Alcohols can also react with chlorinating agents, typically through the haloform reaction, and in some conditions forming dangerously sensitive hypochlorite esters.

That "extremly noxious/lachrymatory gas" was likely chloroacetone.

TCCA partially hydrolyses in water forming hypochlorous acid, HOCl, and cyanuric acid. Acidic conditions shift the equilibrium towards the formation of hypochlorous acid.

[Edited on 24-2-2012 by AndersHoveland]

Endimion17 - 24-2-2012 at 07:09

Trichloroisocyanuric acid is unstable. That's why it smells of chlorine and it's the very same reason why it is used for known purposes.

I don't think it was nitrogen trichloride. I know the lachrymatory gas you're speaking of, but don't know what that is. It's invisible and VERY irritating, gets a lot worse if you rub your eyes. Literally scares the tears out of your poor eyes. It is evolved upon heating salts of this acid, too. I don't recall it being flammable.
Who knows, maybe a crystal precipitated at the bottom of the beaker where it was encased in water vapor bubble and managed to heat itself above the boiling point of the solution. That's a common problem in organics labs, and that's why direct evaporation on the heating plate is rarely used.

Solutions of this acid aren't meant to be boiled. This acid's anion is unstable. You went through all the fuss just to essentially lower the final yield and get a mixture of who knows what.
A different solvent should be used, and at it should be done at low temperature.

Bot0nist - 24-2-2012 at 07:11

I have read many incidents and warnings involving using TCCA on this site. Mostly during halogenation that are vigorous to begin with. Often the problem occurs when the reagent is added to quickly, or if the temperature increases are not controlled. I am not really sure about what decomposition products came into play, but it sounds scary.

While the solution was boiling away did you have any stirring going on? Magnetic stirring often helps reduce any hot spots in the lowest layers of the solution, nearest the heat source. This is compounded greatly when a solid sediment is present, because it insulates the small amount of liquid under and around it allowing it to heat up very hot, and quickly.

EDIT: Thanks for chiming in Anders. I expect you and AJOKER to post pages.

[Edited on 24-2-2012 by Bot0nist]

bahamuth - 24-2-2012 at 10:05

Quote: Originally posted by weiming1998

If it still doesn't work, then use something like dichloromethane or any highly chlorinated solvents to dissolve the TCCA. Then dissolve in water and evaporate in a wide container.

My initial plan was to use dichloromethane and rotavap the product to dryness, but the DCM and my normal size Rotavapor is located in a storage 200km away atm.

Quote: Originally posted by AndersHoveland

That "extremly noxious/lachrymatory gas" was likely chloroacetone

There was no evolution of smell when the acetone/TCCA solution was steam bath dried, so not likely. And if it smells/feels anything like the iodo derivative this was not. The feeling was more "chlorine gas" like if I should describe it..

Quote: Originally posted by Endimion17

Who knows, maybe a crystal precipitated at the bottom of the beaker where it was encased in water vapor bubble and managed to heat itself above the boiling point of the solution. That's a common problem in organics labs, and that's why direct evaporation on the heating plate is rarely used.

The TCCA floated, but as you said it could have been a crystal formation which decomposed. I was 1 m away and could not really see the solution "jumping" or anything like that so definitivly the "pop" happened in the vapor phase. May add that this was a "infrared" heat source at maximun juice, a hotplate like the ceramic tabletops.

Quote: Originally posted by Bot0nist

While the solution was boiling away did you have any stirring going on? Magnetic stirring often helps reduce any hot spots in the lowest layers of the solution, nearest the heat source.

No stirring, but 4 large effective glass bead boiling stones. I usually look for this things and there was a vigorous turnover of the solvent and I deemed it sufficient.

May note that this was a pilot run, had no real expectations of any product. Additionally I was kinda expecting it to decompose but not like it did..

Thanks for the input but I am still left with the question, what decomposed violently as to give a boom/pop.

PS. Please do not turn this thread into a battlefield of unscientific crap... There is enough of other forums to do that on.

Edit: Apparently hypochlorous acid may indeed detonate at elevated temperatures and it may very well be that phenomenon I observed.

Of gaseous hypochlorous acid

And it may have been traces of sodium carbonate forming sodium hypochlorite further reacting with hypochlorous acid causing the "detonation" as mentioned in several MSDS on both compounds.

[Edited on 24-2-2012 by bahamuth]

weiming1998 - 25-2-2012 at 00:34

Quote: Originally posted by bahamuth

Quote: Originally posted by weiming1998

If it still doesn't work, then use something like dichloromethane or any highly chlorinated solvents to dissolve the TCCA. Then dissolve in water and evaporate in a wide container.

My initial plan was to use dichloromethane and rotavap the product to dryness, but the DCM and my normal size Rotavapor is located in a storage 200km away atm.

[Edited on 24-2-2012 by bahamuth]

Then, instead of dichloromethane, use your original acetone and some hypochlorites(calcium hypochlorite seems to be better than sodium for this purpose, because the reacted and unreacted substances can be filtered out, and is not contaminated with water) to make chloroform (excess hypochlorite, or acetone will remain!), then dissolve the TCCA in it. Pour the solution onto a wide plate under the sun OUTSIDE, because small amounts of phosgene will form.
That should evaporate quite quickly, and then you are left with some TCCA at a reasonable purity. No rotary evaporators or fancy apparatuses needed.

bahamuth - 25-2-2012 at 04:21

Are you telling me how to make chloroform, and the safety precations!?

If you read my profile you might see that I list that I am educated to handle chemicals, offcourse the more exotic ones I have little experience with but chloroform.... Also, we don't have much sun in Norway ATM, just lots of wind and snow

The reason I used acetone is that I had data on that TCCA would be soluble in it and it won't give me cancer. Plus I hate the smell, got sensitized while working with it for prolonged periodes at work and by distilling huge amounts of Bligh & Dyer lipid extraction waste at home.

And if you wanted to help you should have linked to a thread about the haloform reaction so one might read of the proper ways to do it. The way you wrote it (sorry if I step on any toes) looks like a meth cook recipe...

weiming1998 - 25-2-2012 at 04:52

Quote: Originally posted by bahamuth

Are you telling me how to make chloroform, and the safety precations!?

If you read my profile you might see that I list that I am educated to handle chemicals, offcourse the more exotic ones I have little experience with but chloroform.... Also, we don't have much sun in Norway ATM, just lots of wind and snow

I have not seen your profile, and you do not need to be smug about it. Obviously it reacts with acetone to form some strange solid, and DCM is very far away from you, so that is your only choice. Probably work outside with the wind blowing the vapours away to avoid breathing it in.

Also, you want a verified link? Here it is http://en.wikipedia.org/wiki/Haloform_reaction

[Edited on 25-2-2012 by weiming1998]

entropy51 - 25-2-2012 at 10:29

Quote: Originally posted by bahamuth

If you read my profile you might see that I list that I am educated to handle chemicals, ...

Apparently TCCA is not a chemical.

bahamuth - 25-2-2012 at 10:36

Quote: Originally posted by entropy51

Quote: Originally posted by bahamuth

If you read my profile you might see that I list that I am educated to handle chemicals, ...

Apparently TCCA is not a chemical.

Hehe, in this day and age I often find myself having such discussions of what is and isn't chemicals with quite a few people, though not on this particular substance of matter.

Anyhow entropy51, you seems like a knowledgable person, do you have an academic suggestion of what decomposed violently?

entropy51 - 25-2-2012 at 10:47

Quote: Originally posted by bahamuth

Anyhow entropy51, you seems like a knowledgable person, do you have an academic suggestion of what decomposed violently?

Not offhand, but there is quite a bit in the safety literature regarding TCCA mishaps. Based on what I have read I'm a little surprised that members of the forum have not reported more problems. There was a post some time ago about an explosion I believe. I have a few papers somewhere that I will try to find.

I do know that it will chlorinate ketones, as you discovered. There is at least one thread on that method for chloroacetone and I think there was a runaway.

Satan - 25-2-2012 at 14:26

Acetone can be used if there is no acid present. As a matter of fact I did run a oxidation reaction in acetone with pyridine as HCl scavenger, adding TCCA solution in acetone dropwise. Uneventful.

Ethyl acetate is also a good solvent for TCCA. Sulfuric acid is also used for purification of TCCA.

Vigorous water reaction in first post was a hydrolysis. Sodium carbonate in water is a base. Your result was solution of cyanuric/chlorocyanuric, chloride, chlorate(I) and sodium ions.

Again, ACETONE is quite inert to TCCA if there is no acid.

Quote: Originally posted by entropy51

I do know that it will chlorinate ketones, as you discovered. There is at least one thread on that method for chloroacetone and I think there was a runaway.

Need catalyst.

There is recently added article in references about it, if I remeber correctly.

[Edited on 25-2-2012 by Satan]

AndersHoveland - 25-2-2012 at 14:41

Quote: Originally posted by Satan

Acetone can be used if there is no acid present. As a matter of fact I did run a oxidation reaction in acetone with pyridine as HCl scavenger, adding TCCA solution in acetone dropwise. Uneventful.

That may be because the chloroacetone immediately reacted with the pyridine. (I know that methylene chloride can read with pyridine) It would form something like:
C5H5N[+]-CH2COCH3 Cl[-]

Polverone - 25-2-2012 at 15:00

I think that the acetone may be a red herring. TCCA in acetone is stable, at least in the short term. The reaction to form chloroacetone is manageable if you add a small amount of sulfuric or phosphoric acid, or it can catch you by surprise when the slow reaction without external acid reaches a critical point of thermal runaway or autocatalysis. But the trouble occurred after solid TCCA had already been recovered and was dissolved in water.

According to Bretherick's Handbook of Reactive Chemical Hazards on TCCA,

"If mixed with a small amount of water, the conc. solution (with pH around 2) may explode, owing to evolution of nitrogen trichloride. It is believed that hydrolysis leads to formation of hypochlorous acid and dichloro-s-triazinetrione, and the protonated acid then attacks the C=N bonds in the triazine ring leading to formation of chloramines and nitrogen trichloride. The dichloro compound is stable to acid in absence of hypochlorous acid."

In your case it makes sense that the explosion could take place in the vapor phase, since the boiling solution would not retain nitrogen trichloride as a liquid.

According to US patent 2,828,308, TCCA may be purified by dissolving in concentrated sulfuric acid and then diluting into ice water.

bahamuth - 25-2-2012 at 16:15

Quote: Originally posted by Polverone

According to US patent 2,828,308, TCCA may be purified by dissolving in concentrated sulfuric acid and then diluting into ice water.

I'll try this when I get the time.

I don't really need it right now but wanted to get a pure compound as to open doors to several syntheses I've read about on this forum, also it helps the motivation to have a reagent at hand, or atleast the know-how and experience to purify it from readily available sources.

Nicodem - 26-2-2012 at 03:37

I just like to quote myself:

Quote: Originally posted by Nicodem

I issued warnings about TCCA many times and still accidents like this happen. I really do not understand why people underestimate the dangers of such powerful oxidants. For example, the accident that happened to Hinz was the consequence of his own carelessness and his unthoughtful "modification" of the acetone chlorination otherwise nicely described in the patent. Things like this are common. I saw other examples of members posting their use of TCCA in irresponsible way (and doing their first experiments on a huge scale!). In the particular case described in this thread it is quite obvious what happened. The guy forgot to quench the reaction with sulfite and distilled the whole reaction mix still containing the oxidant and the acid thus causing Cl2O formation and disproportionation to chlorine dioxide which together with organic vapors form a terribly light sensitive explosive gas phase. While working in the lab only thinking about what you are doing can save you from injuries or even death. I'm glad he described his accident as this might give some thought to all those who start their first reactions on a huge scale without thinking much what they are doing. And of course it is nice to hear he got trough it without glass shrapnels in his face.

So, here we have TCCA, water, heat and traces of acetone. Looks like another chlorine oxides explosion to me.