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Author: Subject: Organic chlorinations
madscientist
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[*] posted on 14-6-2002 at 17:09
Organic chlorinations


Has anyone successfully carried out an organic chlorination? I recently attempted to chlorinate acetic acid with chlorine gas in the presence of ultraviolet light and a tiny amount of sulfur - after 15 minutes of exposure to chlorine gas, there was no noticeble change in mass.

Chlorinations with SCl2 or S2Cl2 probably will work much better, but will be more dangerous for me to carry out (my gas mask doesn't scrub sulfur chlorides or hydrogen sulfide).




I weep at the sight of flaming acetic anhydride.
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[*] posted on 20-6-2002 at 11:19


Have you tried chlorine in statu nascendi, that is forming it in the reaction vessel, for example by adding KMnO4 and HCl to it. Maybe add some NaCl to the solution and electrolyse, also produces reactive chlorine.

You should collect the chlorine gas and pass it throug a warm NaOH/NaHCO3 solution, this will convert it to sodiumchlorate.
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[*] posted on 20-6-2002 at 12:38


I've been interested in chlorinating acetic acid recently. One in situ method I thought of was to mix solid lithium or calcium hypochlorite with the acid and then distill. I tried with calcium hypochlorite. Unfortunately, the acid was unchanged. Some sort of catalyst is definitely needed.

I've seen a few different catalysts mentioned (in ACS articles I was searching, sorry I don't have the references handy). Sulfuryl chloride plus heat and chlorine will chlorinate acetic acid.

Unfortunately, sulfuryl chloride is really nasty stuff, I don't know how to make it, and the yields (in any case) weren't spectacular, something like 30%-50%.

Another method - apparently the "standard" - is to use PCl3 as the catalyst. Gosh, if only I could pick *that* up at Sears.

Yet another method is to add red phosphorus to the acid, heat, and bubble chlorine (I'm guessing this forms the chloride in situ). This one is just at the edge of possibility for me. But - ugh - I'd have to collect the phosphorus from match books. Won't that be tedious. Plus the phosphorus thus obtained is of dubious purity. It's becoming apparent that what I really need is my own furnace for producing phosphorus, or some clever low-temperature method that I haven't yet seen.
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vulture
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[*] posted on 21-6-2002 at 05:42


I wonder why you use, hypochlorite, that doesn't yield chlorine at all, only oxygen.
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[*] posted on 21-6-2002 at 08:22


Quote:
I wonder why you use, hypochlorite, that doesn't yield chlorine at all, only oxygen.


Really? The dry granules stink of chlorine and when I added them to the acetic acid there was a considerable chlorine scent also. It was sold as a chlorine-adding agent for swimming pools. The JT Baker MSDS says "Reacts with water and acids giving off chlorine gas."

[Edited on 21-6-2002 by Polverone]
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[*] posted on 21-6-2002 at 14:46


Quote:
Originally posted by vulture
You should collect the chlorine gas and pass it throug a warm NaOH/NaHCO3 solution, this will convert it to sodiumchlorate.


vulture? have you had any success with this? i am thinking about trying this myself (with NaOH)
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[*] posted on 23-6-2002 at 23:51


Haven't tried it myself, but the procedure is used in the industry to produce chlorate.

The idea is that the Cl2 reacts directly with the NaOH to form NaClO3 while the NaHCO3 will neutralize any chlorine acids present in the solution. Depending on the temperature you get hypochlorite or chlorate.

The intention was to provide a way of safely disposing the chlorine gas.

Polverone, I always found that hypochlorite very odd stuff.
Think about it, what should happen when it yields chlorine gas?:

2NaOCl -> Cl2 + ?

As when it yields singular oxygen:

NaOCl -> [O] + NaCl

[Edited on 24-6-2002 by vulture]
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smile.gif posted on 24-6-2002 at 05:53


This is what happens when NaOCl reacts with HCl :
4NaOCl + 4HCl --> 4Na(+) + 4Cl(-) + 4OCl(-) + 4H(+) -->
4NaCl + 4HClO-> 4NaCl + 2H20 + O2 + 2Cl2

The same happens with other acids also.
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[*] posted on 25-6-2002 at 12:22


I agree that hypochlorites are odd. They can yield chlorine, oxygen, and chlorine monoxide. Don't ask me exactly how they do it.

Thinking of hypochlorites made me start thinking of other over the counter chlorinating agents. What about trichlorisocyanuric acid, commonly used in tablets for chlorinating pools? I started doing some research and came up with some interesting stuff. I found an article in Organic Process Research and Development "Trichlorisocyanuric Acid: A Safe and Efficient Oxidant." The authors report on a number of different chlorinations and oxidations. I cannot post the full article, obviously, but I could summarize it or the more interesting parts of it if there were interest.

The authors' review of the literature found that this chemical hasn't much been used in the lab even though it has been produced for industrial purposes for decades. This suggests to me that there is possibly room for novel and interesting amateur experimentation. And it is certainly a readily available and inexpensive substance.
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[*] posted on 8-7-2002 at 01:09


I've seen that stuff, those bottles always carry warnings about poisonous gas release with acids. I wonder if they mean Cl2 or (CN)2?
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[*] posted on 1-11-2002 at 13:10


Here's an idea that just occurred to me.

Why not add a stoichemitric quantity of a dry ammonium salt (preferrably ammonium chloride) to the organic substance to be chlorinated, and pass dry chlorine gas through the mix? Ammonium salts easily form nitrogen trichloride when chlorine gas comes in contact with them, and nitrogen trichloride should be a great chlorinating agent. Basically, the ammonium chloride would be a "catalyst" that got used up in the reaction.




I weep at the sight of flaming acetic anhydride.
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[*] posted on 6-12-2002 at 20:35


Seems that calcium hypochlorite can be used for organic chlorinations after all: http://www.rhodium.ws/chemistry/benzylchloride.html

I suppose this is how the reaction proceeds:

2PhCH3 + Ca(OCl)2 ----> 2PhCH2Cl + Ca(OH)2




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[*] posted on 6-12-2002 at 21:01


Yes... that's one of the things that inspired me to try using it on acetic acid. Not all chlorinations are equally easy, of course. On the Hive itself I have seen it suggested that pure lithium hypochlorite is superior to calcium hypochlorite for that particular reaction (toluene chlorination).

Hypochlorites have the somewhat undesirable ability to give up oxygen as well as chlorine, and reactions using them can easily get out of hand. The brief writeup on Rhodium's site doesn't mention it, but if the temperature rises too high then the reaction can easily lead to fire/explosion instead of chlorination.
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[*] posted on 10-6-2003 at 18:27


I hope this is recognized as a delta: <strike>^</strike>

2NaOCl -<strike>^</strike>-> 2NaCl + O<sub>2</sub>

2NaOCl -<strike>^</strike>-> Na<sub>2</sub>O + Cl<sub>2</sub>

Who knows, this may actually happen:
12NaOCl -<strike>^</strike>-> 4ClO + 8NaCl + 2Na<sub>2</sub>O + 3O<sub>2</sub>

[Edited on 11-6-2003 by blip]
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[*] posted on 12-6-2003 at 16:46


vulture: Chlorates are not made by reacting chlorine gas with caustic soda. They do use caustic scrubbing to remove chlorine from the hydrogen stream coming off the electrolysis cells.

Hypochlorite is made in these scrubbing towers and is recycled back into the cell liquor.

I've never heard of hypochlorites giving off oxygen, only chlorine.
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[*] posted on 12-6-2003 at 17:30


NaOH + Cl<sub>2</sub> <sup><u>__</u></sup>> NaOCl + HCl

HCl + NaHCO<sub>3</sub> <sup><u>__</u></sup>> NaCl + CO<sub>2</sub> + H<sub>2</sub>O

3NaOCl <sup><u>_warm_solution_</u></sup>> 2NaCl + NaClO<sub>3</sub>

KCl(aq) + NaClO<sub>3</sub>(aq) <sup><u>_cold_solution_</u></sup>> KClO<sub>3</sub>(s) + NaCl(aq)




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[*] posted on 12-6-2003 at 19:44


Yes hypochlorates give off singlet oxygen, a redish glow.

CTR




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[*] posted on 12-6-2003 at 21:51
Try using FE as a promotor


When performing chlorination in the presence of UV use FE as a promoter...Iron powder or even iron tacks will work...Also be sure the chlorine is dry.;)
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[*] posted on 12-6-2003 at 21:57
Polverone use thionyl chloride


You can use either thionyl chloride or better yet PCl5...Thionyl chloride can be made without to much trouble.
:o
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[*] posted on 13-6-2003 at 04:20


You're guys are mixing things up!

Hypochlorites will yield chlorine with HCl because it oxidizes the Cl- of the HCl to Cl2!

2HCl + NaOCl --> Cl2 + NaCl + H2O

When simply heating hypochlorites they will only lose oxygen.

Very strong acids will yield chlorinemonoxide I suspect.

[Edited on 13-6-2003 by vulture]




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[*] posted on 13-6-2003 at 06:14


Thanks vulture for this explanaition. I want to add that there is at least with aromatic molecules a big difference to make in reaction conditions and catalyst/no catalyst if you want to halogenate the ring or the chain.

And yes madscientist I tried several chlorinations (w/w success), mostly aromatics on the chain.

Florida_Alchemist: might you disclose how you make thionylchloride? Ways to this versatile compound are always welcome!
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