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Author: Subject: p-dichlorobenzene -> chlorobenzene?
stygian
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[*] posted on 1-2-2005 at 12:27
p-dichlorobenzene -> chlorobenzene?


My question is straightforward, what ways are there to do this?
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vimal
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[*] posted on 1-2-2005 at 17:43


you can try out the Grignard Stepwise degradation. use exactly 1eq of paradichlorobenzene and treat it with exactly 1eq of Mg in (what you know!) ether. then, remove the -MgCl by H2O...

is that ok?

maybe for a paper reaction?

see reaction number 163 at the Merck Index. :)

[Edited on 2-2-2005 by vimal]




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chemoleo
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[*] posted on 1-2-2005 at 17:47


Didn't someone earlier post this wouldnt work well, you'd have to use p bromo chlorobenzene?



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stygian
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[*] posted on 2-2-2005 at 09:01


What about this. From an older discussion:

Quote:

This is a research project idea for the home experimenter: Para Dichlorobenze mothball substitute can probably be used in a home lab for making other reagents if you 1st try to substitute one of the chlorines with Iodine...Very old and mostly overlooked method. then you can remove the iodine and get chlorobenzene.


How do you go about doing something like this?
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trilobite
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[*] posted on 2-2-2005 at 12:54


See my post in the thread Grignard Reagent 4-chlorophenylmagnesium bromide. If you are talking about the Finkelstein swap reaction I will have to tell you it only works on aliphatic halogens per se and is hardly a forgotten reaction. Adding a catalytic amount of iodide salt is a standard trick. There was an aromatic version of the reaction described in Tetrahedron Letters if I remember correctly. It takes a Cu(I) salt catalyst and the right solvent though (1,2-dichloroethane gave the best results).
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[*] posted on 2-2-2005 at 13:18


I wonder if this is of use (...no ether required.)

Organic Syntheses, Coll. Vol. 5, p.998; Vol. 47, p.103
REDUCTION OF ORGANIC HALIDES. CHLOROBENZENE TO BENZENE

...can't seem to link to that one so you'll have to look it up yourself.

[Edited on 2-2-2005 by UpNatom]
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FloridaAlchemist
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[*] posted on 2-2-2005 at 19:20
Here is a possible method to use


1st convert the 1,4 Dichlorobenzene to
1,4 Dichloro-2-Nitrobenzene with a strong nitrating agent . . Once you have this intermediate, this will allow you to remove the chlorine.;)
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[*] posted on 2-2-2005 at 19:47


A little word of warning on the nitrating method, though...A couple months ago, I put a shitload of research into the conversion of p-dichlorobenzene to hydroquinone. My attempts at simply replacing one chlorine failed miserably, so I tried deactivating it through nitration first.

A hot nitrating bath of H2SO4/KNO3 in roughly 2x molar amounts of nitric did a decent job at nitrating the molten p-dcb. Unfortunately, I found it impossible to find ANY information at all about this new compound. So, being the (idiot) genius (dumbass) that I am, I assumed (stupidly) that the new nitro compound would have similar characteristics to p-dcb.

Oh, was I ever wrong. Physically, it is a semi-crystaline, powdery yellowish off-white substance. I allowed it to dry for some time, but it didn't seem to dry out. I touched the filter it was in, and it seemed quite dry, though covered in the compound. I wiped my hands on my pants afterwards, and no residue was left on them - or so I thought. To make an already long story short, 1,4-dichloro 2-nitrobenzene is incredibly irritating. My skin is quite resillient, so it didn't have much much of an effect. It did, however, wreak havoc on my eyes, nose, mouth, lips, and throat. It seemed like a mix between fire and alcohol, burning and just plain destroying my facial orifices. There was no real physical damage, but it did hurt like hell.

It was easy enough to make, but don't let it fool you...Gloves are a MUST when handling this chemical...Heed my advice, or you'll fall victim to the same fate I did.
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[*] posted on 2-2-2005 at 19:53


Thanks for the reference UpNatom, that is one easy and very useful procedure that I will be sure to try with many reagents soon. And everything is fairly avalible, yay!



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12AX7
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[*] posted on 4-5-2005 at 12:00


Don't suppose it's possible to bubble Cl2 through molten p-DCB to eventually fully chlorinate it?

Tim
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[*] posted on 24-4-2018 at 15:05


Quote: Originally posted by 12AX7  
Don't suppose it's possible to bubble Cl2 through molten p-DCB to eventually fully chlorinate it?

Tim


I'm not sure if it'd work...you'd need a UV source if anything.




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[*] posted on 24-4-2018 at 15:10


Quote: Originally posted by Velzee  
Quote: Originally posted by 12AX7  
Don't suppose it's possible to bubble Cl2 through molten p-DCB to eventually fully chlorinate it?

Tim


I'm not sure if it'd work...you'd need a UV source if anything.

Surely AlCl3 or FeCl3 as a catalyst instead....




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[*] posted on 24-4-2018 at 15:49


Quote: Originally posted by stygian  
My question is straightforward, what ways are there to do this?


You may try to dehalogenate the dichloro compound with the NH4Cl, zinc, THF system, like said in the paper attached below.

However, I'm not sure, and the paper said nothing about this, if the reaction will stop on mono-dechlorination or if it would produce benzene too. May be stoichiometric amounts of the reagents favours mono-dehalogenation instead doble dehalogenation of the ring. I think this kind of reaction may result a mix of monochlorobenzene and benzene, I guess.

Attachment: Dehalogenation with Zinc, NH4Cl and THF.pdf (60kB)
This file has been downloaded 402 times

[Edited on 25-4-2018 by Chemi Pharma]
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