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vulture
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I2 and Toluene frustrations
Okay, here's one of my personal lab frustrations.
I wanted to make benzylbromide and visited my favourite shop to get some KBr. Unfortunately it was out of stock, so I bought some KI to make
benzyliodide.
I proceeded to make elemental I2 with H2O2 and H3PO4 and mixed the unpurified product with toluene.
The mixture was placed in a flask and refluxed under the influence of UV light for several hours. There was no noticable reaction.
Here's where the trouble started. As I started heating the I2/toluene mixture, I noticed that the I2 sublimed as fast from the mixture as the
toluene evaporated, that is, the I2 was as high up in the cooler as the toluene. I proceeded to distill some of the mixture over to see if any product
formed.
As I suspected, the destillate consisted of an emulsion which I separated by filtration over MgSO4. The milky water layer was a very strong irritant,
30 seconds of exposure would have me crying my eyes out and being unable to open them.
As I still had alot of unreacted toluene/I2 mixture I started distilling that over a 30cm vigreux column to recover the toluene. Atleast, that's
what I wished. The vigreux column stopped alot of I2, but the toluene at the top still had a faint pink color. After some time of distilling the
iodine would even dominate the toluene vapor.
Anybody got any good ideas how to separate them?
Picture of I2/toluene in liebigcooler attached.
Yes, yes I know a liebig aint good for refluxing. I've got two intensive and 1 dimroth cooler now. 
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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vulture
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Another picture of the I2 and toluene condensing in the liebig.
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vulture
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Breaking the emulsion over anhydrous MgSO4.
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Organikum
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First.
You cannot make benzyliodide this way. For making benzyliodide you have to make benzylchloride or benzylbromide and to perform an Finkelstein swap
onto this.
Why?
Because the formed HI reduces the benzyliodide instantly back to the hydrocarbon.
(maybe there is a way by adding a compound which instantly eats up the formed HI, an carbonate or a pseudobase, but I am not sure on this)
Recovery:
Add copper filings or powder to the toluene - this will form copperiodide from which you can recover your iodine by means of H2SO4 followed by
sublimation/distillation of the iodine. Sublimation is advised and no big deal.
There are other ways, but thats the most simple one I know.
(Copper in a finely divided state is most conveniantly gained by adding iron (wool) and a dash of NaCl to a strong aqueous solution of CuSO4)
If you want to do an iodination on a compound where this is possible you dont have to make I from KI btw. Just use H3PO4 and KI - anhydrous and you
will iodinate alcohols and stuff.
[Edited on 10-5-2004 by Organikum]
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axehandle
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| Quote: |
(Copper in a finely divided state is most conveniantly gained by adding iron (wool) and a dash of NaCl to a strong aqueous solution of CuSO4)
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I wish there was a similar method for Al....
/A
My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35
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vulture
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| Quote: | First.
You cannot make benzyliodide this way. For making benzyliodide you have to make benzylchloride or benzylbromide and to perform an Finkelstein swap
onto this.
Why?
Because the formed HI reduces the benzyliodide instantly back to the hydrocarbon. |
I'm aware of this now, unfortunately I was not at the time of the experiment.
However, something ackward and very irritating was formed in there. Any idea?
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Organikum
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And vulture, of course you have some benzyliodide in the mixture now - equilibrium and such - but you shouldnt hang your bill to deep into this.
Benzylhalogens are not only strong lachrymators, but they cause nausea, dizziness and more.
This probably causes some of the inconsistencies in your post, like where did the water come from and breaking aqueous emulsions with MgSO4???
I used the opportunity to get me back my base in antartica you stole from me lately - I hope you dont mind.
And I took one of yours in africa as I was at it.....
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vulture
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The water is from the iodine, I made it from H2O2 and H3PO4, producing quite a bit of water.
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Organikum
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uups. I overread this, sorry.
Go for the copperiodide.
btw. I like your experimental style. Reminds me on my own. In special the "crying eyes out" part is well known to me.
Also the "first try, read the textbook later" method is mine.... 
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vulture
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| Quote: |
btw. I like your experimental style. Reminds me on my own. In special the "crying eyes out" part is well known to me.
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Hehe. Does crying your eyes out yet going back 10 times and flushing your eyes ten times again because you NEED to finish something sound familiar
too?
Usually I first read lots, but I noticed that this is something that is preventing me from experimenting! So, I revived the crash & burn method
for once.
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Organikum
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| Quote: |
Hehe. Does crying your eyes out yet going back 10 times and flushing your eyes ten times again because you NEED to finish something sound familiar
too?
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Is this like entering a room full with chlorine again because you can count the seconds until the overpressurized chlorine generator will explode?
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vulture
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ABSOLUTELY.
Yeah.
Sjeez are we going off-topic.
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acx01b
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if you add some NaOH you'll get NaIO NaI and C6H5-CH2-OH
extract it and then put the iodine back with concentrated HI !
but copper looks cool too.
[Edited on 11-5-2004 by acx01b]
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vulture
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The benzyliodide yields are extremely small, so no use doing that.
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frogfot
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| Quote: | Originally posted by Organikum
Is this like entering a room full with chlorine again because you can count the seconds until the overpressurized chlorine generator will explode?
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Yay, a dejavu... and cry from benzyl bromide is something familiar too 
Anyway, benzyl chloride synth seems to be simple to carry out:
C6H6 + HCHO + HCl -ZnCl2-> C6H5CH2Cl + HCl
Aqueous formaldehyde and dry HCl is simple to prepare, benzene should be available in some countries (me not being lucky to live in such country  )
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vulture
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Photochlorination of toluene should be easier, the tricky part is getting a reliable stream of chlorine into the reaction mix for several hours.
That's why benzylbromide was my first goal.
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acx01b
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what is the role of formaldehyde ???
wow ok its double addition ???
1st benzyl alcohol formed ?
[Edited on 12-5-2004 by acx01b]
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Organikum
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| Quote: |
the tricky part is getting a reliable stream of chlorine into the reaction mix for several hours.
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I am working on it.
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Organikum
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You can also use the method of Loomis:
hypochlorite + toluene
This cannot be done using an oilbath as heating has to be stopped immediately when the reaction kicks in or youll get a nice runaway.
Be careful!
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vulture
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This cannot be done using an oilbath as heating has to be stopped immediately when the reaction kicks in or youll get a nice runaway.
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This sounds like steamheating to me.
That is, have a source of steam which you can cut off or bypass immediatly.
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Organikum
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Either this or a heating mantle which can be removed very fast, or thy famous "airbath" easy to improvise with a hot-air pistol and some
Al-foil.
The patent is:
US1280612
It works as described but,
- no ironpot or other metal for this catalyzes ringchlorination and hypochlorite instead of bleaching powder.
and,
- The Hypochlorite has to be bonedry! Fresh from the box is ok, but not some stuff which stood a few days open to air.
Its actually not hard. BzCl can be steamdistilled and it forms an azeotrope with toluene btw.
The hot-air pistol driven airbath is useful for many other reactions too of course.
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vulture
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I'm a bit wary though how my glass will respond to flash heating/cooling by the hot air bath method.
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DDTea
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| Quote: | Anyway, benzyl chloride synth seems to be simple to carry out:
C6H6 + HCHO + HCl -ZnCl2-> C6H5CH2Cl + HCl
Aqueous formaldehyde and dry HCl is simple to prepare, benzene should be available in some countries (me not being lucky to live in such country )
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Sounds like Cancer soup! Formaldehyde and Benzene can be bad enough, but the
addition of HCl will form bis(Chloromethyl) ether. This is extremely toxic and irritating, and is an OSHA-regulated Carcinogen. However, I've
heard of people working with it without much fear...it's all about respect for the chemicals. Nevertheless, this would be a reaction to be
careful with.
On the other hand, bis(bromomethyl) Ether can be prepared by the reaction between Paraformaldehyde, Sodium Bromide, and Sulfuric Acid. If
bis(chloromethyl) ether can be used to chlorinate Benzene, perhaps the bromo variant could be used for the same thing.
Alternately, though I have not heard much about it, there is bis(iodomethyl) ether.
But this gives me another idea. Many classical chemical weapons are good for halogenations (Phosgene, for example), and are also very easy to
prepare. So, perhaps by preparing a Iodo-derivative of them (Iodoacetone, maybe?), it could be reacted with Toluene to produce Benzyl Iodide:
CH3COCH2I + C6H5-CH3 --> CH3COCH3 + C6H5-CH2I
I also remember someone reporting of a lachrymator being made by reacting I2 with Isopropyl Alcohol...maybe this could be used too.
However, this would be a very complicated way to produce a simple substance--and I'm just speculating here.
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vulture
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I also remember someone reporting of a lachrymator being made by reacting I2 with Isopropyl Alcohol...maybe this could be used too.
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It was the infamous Ph Z.
However, I've added some iodine myself to isopropyl alcohol and observed no reaction, even after several days. I can still safely take a whiff of
the mixture.
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madscientist
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I thought iodine just wasn't reactive enough to react with toluene...
I weep at the sight of flaming acetic anhydride.
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