Sciencemadness Discussion Board - I2 and Toluene frustrations

I2 and Toluene frustrations

vulture - 10-5-2004 at 11:42

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.

vulture - 10-5-2004 at 11:45

Another picture of the I2 and toluene condensing in the liebig.

I2_toluene2.jpg - 89kB

vulture - 10-5-2004 at 11:49

Breaking the emulsion over anhydrous MgSO4.

I2_toluene3.jpg - 88kB

Organikum - 10-5-2004 at 12:16

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]

axehandle - 10-5-2004 at 13:16

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)

I wish there was a similar method for Al....

/A

vulture - 10-5-2004 at 13:24

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?

Organikum - 10-5-2004 at 13:38

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.....

vulture - 10-5-2004 at 13:56

The water is from the iodine, I made it from H2O2 and H3PO4, producing quite a bit of water.

Organikum - 10-5-2004 at 14:10

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....

vulture - 10-5-2004 at 14:15

Quote:

btw. I like your experimental style. Reminds me on my own. In special the "crying eyes out" part is well known to me.

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.

Organikum - 10-5-2004 at 14:27

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?

Is this like entering a room full with chlorine again because you can count the seconds until the overpressurized chlorine generator will explode?

vulture - 10-5-2004 at 15:03

ABSOLUTELY.

Yeah.

Sjeez are we going off-topic.

acx01b - 10-5-2004 at 16:10

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]

vulture - 11-5-2004 at 09:55

The benzyliodide yields are extremely small, so no use doing that.

frogfot - 11-5-2004 at 14:26

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?

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

)

vulture - 11-5-2004 at 14:37

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.

acx01b - 11-5-2004 at 19:05

what is the role of formaldehyde ???

wow ok its double addition ???

1st benzyl alcohol formed ?

[Edited on 12-5-2004 by acx01b]

Organikum - 12-5-2004 at 01:28

Quote:

the tricky part is getting a reliable stream of chlorine into the reaction mix for several hours.

I am working on it.

Organikum - 12-5-2004 at 02:03

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!

vulture - 12-5-2004 at 10:24

Quote:

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.

This sounds like steamheating to me.

That is, have a source of steam which you can cut off or bypass immediatly.

Organikum - 12-5-2004 at 14:16

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.

vulture - 12-5-2004 at 14:24

I'm a bit wary though how my glass will respond to flash heating/cooling by the hot air bath method.

DDTea - 12-5-2004 at 14:58

Quote:

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.

vulture - 12-5-2004 at 15:04

Quote:

I also remember someone reporting of a lachrymator being made by reacting I2 with Isopropyl Alcohol...maybe this could be used too.

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.

madscientist - 12-5-2004 at 19:42

I thought iodine just wasn't reactive enough to react with toluene...

thunderfvck - 12-5-2004 at 21:12

^

Yeah?

Forgive me as I haven't read the entire post with my full attention, but wouldn't you need a catalyst? It's cramming time for my oragnic II test this Friday, and to halogenate benzene you need a catalyst, FeCl3 or whichever (in the limited perspective of my course on the varities of catalysts). Toluene with its methyl group only slightly activates the ring to ortho/para substitution....Anyways, maybe I'm missing something that you've already mentioned...

madscientist - 13-5-2004 at 02:35

The UV light catalyzes the reaction of halogens with toluene we're discussing. It breaks the halogen-halogen bond, creating very reactive free radicals. Heat can sometimes do the trick. Alternative catalysts for this reaction are organic peroxides.

Organikum - 13-5-2004 at 02:46

Thunderfuck:
vulture wanted a sidechainhalogenation no ringhalogenation

Madscientist:
Maybe youre basically right, dont know, but some iodination takes place for sure.

vulture:
You shall not direct your hot air gun at maximum heat directly onto the flask but you may use a lower power setting and tangential input of the hot air of course. So the air goes round and round between Al-foil and flask, let a small slit between foil and flask for it to escape there and you will be fine.
You can even heat a mason jar this way.

frogfot - 13-5-2004 at 06:42

Quote:

Originally posted by acx01b
what is the role of formaldehyde ???
wow ok its double addition ???
1st benzyl alcohol formed ?

ZnCl2 suppose to make nucleophile from formaldehyde, which will in turn attack benzene.. so, yeah alcohol is formed. I guess HCl substitutes hydroxyl (this is probably catalysed by Zn2+ or H+)

Samosa, that synth seemed to be easy to perform with regard to reagents, but yeah, now it seems a bit to dangerous..
Maby by changing the acid and salt catalyst one would avoid formation of chloromethyl.

[Edited on 13-5-2004 by frogfot]

vulture - 13-5-2004 at 06:54

I already pointed out that it isn't possible to make benzyliodide from I2 + toluene and Organikum already pointed out why.

Is it too hard to read a page of replies? Let's not go around in circles please.

I'll have to look into this hotair bath, thanks organikum.

Ofcourse, if a catalyst would allow direct reaction between I2 and toluene, I'm all ears.

Furthermore, bombarding the reaction mixture with UV isn't as easy as it seems. Borosilicate glass stops most UV radiation, except the wavelength that is capable of splitting chlorine, but not bromine.

A NS fittable mercury vapor lamp is, well, just bloody expensive! It'll cost me three arms and two legs, which I don't have unfortunately.

Organikum - 13-5-2004 at 08:52

The catalyst of choice for sidechainhalogenations would be red phosphorus. This forms PX3 or PX5 (X=Cl or Br) in situ with the halogen (reaction conditions should be somehow anhydrous here) and halogenates the sidechain fast and selective. Nice here: One PX3 molecule halogenates three toluene molecules at once. Light pushes the reaction foreward but is not essential. Light and phosphorus allow the halogenation to proceed at lower temperatures whats nice regarding the exothermic character of it. But dont get too low as this would cause ringchlorination.

vulture:
A usual 500W halogen lamp - the cheap ones yes, provides enough light for a bromination in borosilcate glassware - no problem.

But a catalytic amount of red phosphorus makes things really easy.

For those who say now:
No phosphorus!
Dont they sell they matchboxes at yours? A catalytic amount is not much. More phosphorus makes the reaction faster but for to get it going tiny amounts suffice.

[Edited on 13-5-2004 by Organikum]

vulture - 13-5-2004 at 10:44

Hmm, so in fact, using PX3 or POX3 as halogenating agents should even be superior to using the halogen itself?

I think I'm going to have to have a chat with a chem supplier...

Organikum - 13-5-2004 at 10:54

Superior? Dont know. The amounts needed would be insane.

This a CATALYST.

vulture - 13-5-2004 at 10:58

What I'm trying to say is that I want to use PX3 as the halogenating agent, instead of using elemental halogens, would that work?

Don't worry about the amounts needed.

Organikum - 13-5-2004 at 11:40

I guess it should.

PCl5 is a wellknown chlorination agent similar or better as thionylchloride as I remember. But its a waste for such a simple task as the halogenation of toluene.
Buy benzylchloride directly and save the PCl5 for somthing serious.

FritzHaber - 14-5-2004 at 04:06

okay, let me extract the essential

1) the reaction PhCH3 + X2 ---> PhCH2-X + HX
is a radical substitution rxn; it isn't an electrophile aromatic substitution or something similar.
as quoted, this reaction needs to be initialised by breaking the X-X (X = halogene) bond to form free radicals, beeing carried out by strong heating, UV-irradiation or by an radical initiator like organic peroxides or diazo-compounds
2) Iodination is, as posted not really possible to do via simple halogenation -- given the poor stability of the C-I bond and the ease, which HI reacts with the aralkyliodide (in fact, this reaction grounds the P/I2 reduction of ephedrine to methamphetamine).
3) the benzyl iodide can be prepared either via nucleophile substitution of BzCl or BzBr with NaI in acetone or DMF ,
or, by a nice reaction:
Ph-CH3 + I-Cl --(hv)--> Bz-I + HCl
iodine monochloride, ICl is prepared by simple reaction between I2 and Cl2 and then purified by fraction-distillation.

[Edited on 14-5-2004 by FritzHaber]

Organikum - 14-5-2004 at 04:45

Quote:

iodine monochloride, ICl is prepared by simple reaction between I2 and Cl2 and then purified by fraction-distillation

Iodine monochloride:
- mp: 27,2°C
- bp: 97°C (decomposition)
Says the Merck Index.

How do you want to fractional distill it when it decomposes? Ok. High vacuum perhaps. But dont forget: ICl forms I2O5 in the presence of air. So vacuum distillation under inert atmosphere? This seems not very practical to me.
At least for those who donr have a complete lab by hand.

The Finkelstein swap - BzCl or BzBr to BzI by NaI in acetone seems much more conveniant.

But vulture seems to be satisfied with any benzylhalogen - no need for exotic tricks.
The most easy one is as I believe the BzBr with red phosphorus as catalyst and some light to speed the reaction up.

FritzHaber - 14-5-2004 at 10:42

okay, reading back, the iodine monochloride isn't really an ideal tool to prepare and work with in a kitchen lab..
also, I realised that it would, unless extreme conditions, as reaction in gaseous phase in presence of radical initiators, far more likely attack the arene ring, so let us forget about ICl

you can made benzyl chloride f.e. from benzyl alcohol, ZnCl2 and HCl(g),
benzyl bromide could be obtained by bubbling chlorine gas through sodium bromide suspension in toluene...using the UV irradiation...but isn't it particulary for benzyl chloride much more easy to obtain it from chem supplier??
I bought some BzCl (100g) from Merck few years ago, no curious questions about purpose or similar..

vulture - 14-5-2004 at 11:13

Where's the satisfaction in buying? I have the precursors, I have enough glass, I have a vacuum pump, etc...

A total workup from OTC compounds is the biggest satisfaction you can get IMHO.

I'm just doing it for the fun of it, no particular goal.

Organikum - 14-5-2004 at 11:35

Quote:

you can made benzyl chloride f.e. from benzyl alcohol, ZnCl2 and HCl(g),

You dont need any ZnCl2 here. Just boiling benzylalcohol with HCl will produce already BzCl.
But we talk toluene here.

Come on vulture! Buildt a chlorine generator and Samosa and I will wellcome you in the famous "chlorine huffer club".

t_Pyro - 15-5-2004 at 09:22

I've got a weird idea! How about oxidizing toluene to benzoic acid, and then reacting it with PBr3? That would produce an acyl bromide. Reducing the carbonyl carbon could be a problem. Would Zn-Hg + conc.HCl work here? If it does, you'd end up with benzyl bromide.

vulture - 15-5-2004 at 10:04

Seems like a sure way to waste PBr3 to me...

Bromination of toluene should be relatively easy compared to chlorination.

I might try this in a few months.

FritzHaber - 15-5-2004 at 10:44

Quote:

Originally posted by t_Pyro
I've got a weird idea! How about oxidizing toluene to benzoic acid, and then reacting it with PBr3? That would produce an acyl bromide. Reducing the carbonyl carbon could be a problem. Would Zn-Hg + conc.HCl work here? If it does, you'd end up with benzyl bromide.

no,
no it won't. upon reduction of acyl halogenides, you usualy obtain initialy aldehyde, this is then further reduced to alcohol, in the benzyl- case even to the starting hydrocarbon (toluene)

t_Pyro - 16-5-2004 at 07:13

Well, if the aldehyde is an intermediate product, I guess the final product will mainly be toluene. Yuck, what a waste of reagents.

Regarding the light energy that is to be provided, how dependent is it on the wavelength of the light? Does the reaction perform better at a specific wavelength, or are shorter wavelengths better?

vulture - 16-5-2004 at 07:40

The wavelength depends on the bond in X-X, that is the halogen used.

Necessary wavelength can be calculated through E = hv and dissociation enthalpy IIRC.

Saerynide - 23-5-2004 at 05:11

How do you store I2? Wrapping the stopper with teflon tape?

thunderfvck - 23-5-2004 at 12:22

I keep mine in the freezer, I don't like the fact that it sublimes like a motherfucker.

I think most people just keep it in a cool, dry place. The usual. With a screw on cap or something so the vapors don't have a chance of escaping.

Saerynide - 24-5-2004 at 05:08

Yeah, but I dont want anything diffusing out. Can you melt teflon tape and use that to seal the glass vial? Or does teflon tape just burn?

Organikum - 24-5-2004 at 10:12

No you cant melt teflon tape. But you dont have to melt it, for it is a sufficent seal if you wrap it in some layers. Over the teflon wrap tightly some usual PVC-tape to keep the teflon from loseneing.

vulture - 24-5-2004 at 12:35

Wetting the teflon with a bit of solvent is enough to make it stick to the joint.

Saerynide - 25-5-2004 at 01:25

Hmph.... No one at the store knew what teflon tape was nor have they ever heard of glass wool. wtf... :mad:

thunderfvck - 25-5-2004 at 01:57

ha!

Glass wool. I can understand. I haven't seen that stuff before.

But teflon tape! My god, were these people born in caves? It's simply barbaric.

Organikum - 25-5-2004 at 05:27

ROTFL !!!!!!!!!!!!

Thunderfuck, you made my day.
Why?
Ask vulture.............

axehandle - 25-5-2004 at 05:44

Quote:

Hmph.... No one at the store knew what teflon tape was nor have they ever heard of glass wool. wtf... :mad:

The do insulate the walls of houses where you live, right? Either they don't or you just happened to ask an extraordinarily retarded store clerk. Try asking for "rockwool". It's sometimes called that. Either that or I suppose I could send you some glass wool... but I simply can't believe it would be impossible to find, anywhere in the world.

edit: Btw, has anyone seen my roll of 0.5mm Nichrotal-80 wire? I know it's somewhere around here ...... oh, no.... wait. Ah.

[Edited on 2004-5-25 by axehandle]

Saerynide - 25-5-2004 at 06:03

I tried asking for "insulation" material too, but I just realized, no one here knows what insulation is... its 33C all year round, houses arent insulated here

I'll try aquarium stores or something later.

vulture - 25-5-2004 at 10:28

Search for yourself. Asking store clerks will get you nowhere, because they're usually the lowest common denominator these days.

I found out when I stopped asking, became a bonehead and searched for myself. Guess what, I found what I was looking for.

Would you work your ass off for 10$ a day? Didn't think so...

Meanwhile, this thread is getting WAAAAAYY off topic.

Organikum - 15-6-2004 at 08:56

Quote:

Meanwhile, this thread is getting WAAAAAYY off topic.

Yes thats actually true. Did I tell you already how fucking hot it is here these days and about the evil storm we had lately? No? Ok, its REALLLLLLY hot here nowadays, but I believe I told this already before...

btw. Photocatalyzed brominations work well with usual light and there is no problem with thick flasks. And chlorinations prefer BLUE light but hey, I did it with a 500W halogen lamp and it worked like a charm!
For chlorinations the temperature should exceed 85°C, but boiliong is not necessary. Lower temperatures favor ringchlorination. I would extrapolate that same is true for brominations, yep.

To the storm: It was such a cruel storm that really BIG trees in park were broken down, I bneliebve trees are not the same quality as the were in the past. But regarding the fact that these trees were quite old I might be wrong here. At least the 2000 years old oak survived - thats a good sign for the future I hope!

Saerenide, you might consider to think. Yes thats what men do with their head and what makes them look so stupid!
Not only isolation from the cold is needed in this world, but insulation from hot parts is also very interesting. Boilers for example. Yes "HOT WATER". Boilers are mostly insulated to keep the water hot. With glasswool for example.
Teflon tape is often plain called "plumbers tape". Have a look.

And it was raining. Streams of water coming down from the sky and the wind was blowing sooo hard that the water came in EVERYWHERE! At least everywhere where I had forgotten to close the window.

Did you recover your iodine now vulture?

ORG