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darel
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[*] posted on 12-7-2008 at 13:18
dioxane


Are there any websites or chemical suppliers that carry this? Is there a synthesis that could be carried out?
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DJF90
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[*] posted on 12-7-2008 at 15:20


Dioxane is a cyclic ether. IIRC, it can be made in a similar fashion to diethyl ether, but using ethylene glycol (ethane-1,2-diol) as the reactant. The conc. sulphuric acid will have to be in more excess than usual as there is more water produced in the reaction.

Dioxane comes in 3 isomers, [1,2], [1,3] and [1,4], the latter of which I believe is the one you are interested in. Needless to say it forms explosive peroxides upon storage, these are explosive and are said to form more easily than ones from diethyl ether or THF :O Also, dioxane is irritating to they eyes and is either a suspected or proven carcinogen (I can't remember). I'm sure there are other warnings you should be aware of but you should search for them yourself.
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stoichiometric_steve
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[*] posted on 12-7-2008 at 23:16


Quote:
Originally posted by DJF90Also, dioxane is irritating to they eyes and is either a suspected or proven carcinogen (I can't remember)


i think is is due to the residual 1,2-dibromoethane which is a precursor. i'm not sure if dioxane itself is a carcinogen.




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len1
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[*] posted on 13-7-2008 at 00:34


Frogfot has a procedure to make dioxane.

Surprisingly in light of what DFJ90 wrote it actually requires much less H2SO4 to dehydrate than the equivalent ether reaction, despite each mole of product releasing two - not one - moleof water.

Why? My explanation is it can be run at a higher T due to the high bp of the alcohol, and lack of competition from elimination, so the H2SO4 dehydrates much better and the water comes over with the product (in which unlike ether its soluble). The H2SO4 thus acts as catalyst.

To the best of knowledge its carcinogenic. Chech all the MSDS. Why? Another mystery of this compound. It very unreactive - as most ethers, so I dont know why.
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DJF90
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[*] posted on 13-7-2008 at 04:11


Maybe I shouldn't speculate so much in future... You're right len1, Frogfot does have a procedure but I'm not sure if the website is working; I tried the link on Bromic's page but it didn't work. You're explanation is perfectly feasable though, something I obviously overlooked.
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len1
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[*] posted on 14-7-2008 at 00:58


I think you should speculate - who cares whoe is right or wrong in the end, I dont know if the solution I posed is right (I think only exp can test that), but if you hadnt speculated I wouldnt have thought on the matter and would have been the poorer.

I think I have the synth somwhere, if the guy who posted cant find Frogfoot Ill repost it

Len
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Panache
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[*] posted on 14-7-2008 at 03:03


If i recall correctly 'dioxane' was once known as the world's 'most toxic' substance, and quoted in one edition of McMurray as such. The next edition omitted this piece of information. The reason being i thought was that the initial lethality testing was performed on some hampsters and basically when you walked into the room with the bottle of dioxane all the hampsters would roll over and die. This led to the quote in the edition of McMurray.
Turns out it was only ever viscously toxic to that particular hamster, other mammals didn't mind the stuff.
Funny if it is true.




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[*] posted on 14-7-2008 at 04:07


1,4-Dioxane is anything but the world's 'most toxic' substance or else you would not find it in practically every lab on the shelve. I never heard about that story about hamsters and I must say I find it very hard to believe. It is a pretty common solvent in organic and analytical labs. It used to be very common as HPLC mobile phase before all this about it being carcinogenic almost phased it out, so that nowadays acetonitrile and methanol become much more common HPLC solvents. Even in inorganic synthesis it finds uses as solvent. I rarely use it as solvent since THF is just as good for most uses where dioxane would be a good choice. However, when you need a reflux at 100°C you can't use THF. It is also much more stable toward electrophiles and acids when compared to the labile THF.

Dioxane is mass produced industrially from ethylene oxide and I suspect it is traces of this precursor that made it appear carcinogenic in the biological tests rather the compound itself.

The reason why etherification of ethylene glycol is simpler than for ethanol could be in that glycols are more basic than ethanol and thus H2SO4 generates more electrophilic species (HO-CH2CH2-O<sup>+</sup>H<sub>2</sub>;) at the same conditions while glycol also being more nucleophylic than ethanol thus both factors working in favor of increasing the reaction rate. Also just speculating out of boredom...

It is in my opinion a waste of time and chemicals to prepare dioxane just because needed as solvent. Prepare it if you want to practice or prove that it can be done, but if you need it as solvent you will probably need lot's of it so either buy it (it's cheap and every supplier sells it) or use another appropriate solvent (plenty alternatives to chose, but depending on the specific use).




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[*] posted on 14-7-2008 at 06:35


Quote:
Originally posted by Panache
If i recall correctly 'dioxane' was once known as the world's 'most toxic' substance, and quoted in one edition of McMurray as such. The next edition omitted this piece of information. The reason being i thought was that the initial lethality testing was performed on some hampsters and basically when you walked into the room with the bottle of dioxane all the hampsters would roll over and die. This led to the quote in the edition of McMurray.


There's a lot of confusion between "dioxane" and "dioxin". The latter term is misused as a generic name for various polychlorinated dioxins, which earned a bad reputation back in the 70's in the wake of a couple of environmental disasters.
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