peter80
Harmless
Posts: 1
Registered: 8-7-2015
Member Is Offline
Mood: No Mood
|
|
Halogenation of xylene
Im investigating the chlorination of xylene. Ive read that
sodiumchlorate + HCl results in free chlorine. Without
catalyst will it chlorinate yust as toluene forming benzyl
chloride ???
and with catalyst results into aromatic-chlorination.
|
|
|
unionised
International Hazard
Posts: 5104
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
"sodiumchlorate + HCl results in free chlorine. "
and also chlorine dioxide, which you probably don't want to play with.
https://en.wikipedia.org/wiki/Chlorine_dioxide
|
|
|
Boffis
International Hazard
Posts: 1836
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
I don't think this process will work very well. In an aqueous medium I think you will get both chlorination and oxidation and therefore end up with a
mixture even in the presence of iron or iodine as a catalyst. I have recently posted an example of this type of chloro-oxidiation under a thread on
caffeine but this is a very different system and is homogeneous because the caffeine is soluble in hydrochloric acid, xylene is not soluble and nor
are the reaction products.
I would suggest generating the chlorine externally and introducing the gas into a suspension of iron in xylene (anhydrous FeCl3 or I2 also would also
work). Check out the references below (sorry they are all in German):
Chlorination of p-xylene to 2-chloro and 2,5-dichloro-p-xylene;
In presence of Iodine - Kluge; Berichte, v18 p2099
In presence of Fe - Willgerodt, Wolfien; J fur Pr Ch., (2) v39 p402
Chlorination with ammonium chloroplumbate(IV) (NH4)2PbCl6 to 2-chloro-4-xylene
Seyewetz & Biot; Comptus rend. v135 1121
Bromination to 2-bromo-p-xylene
Jannasch; Annalen (JLAC), v171 p82 and Berichte v17 p2710
Jacobsen; Berichte v18 p357
Ditto to 2,5-dibromo-p-xylene
Jannasch; Berichte v10 p1357
Ditto to 2,3,5,6 tetrabromo-p-xylene
Jacobsen as above
I haven't checked out o and m xylene but I suspect the later will mainly form the 4-halo-xylene first.
These references and several more I have are for p-xylene because I am interested in derivatives of terephthalic acid but I am sure the conditions
will halogenate the other isomeres too. I preseume you are working with mixed isomer xylene.
Incidently what do you hope to make from the mixture of product you are going to get? OTC xylene is a mixture of about 50-70% m-isomer, 20-30% o and
10-20% p-xylene. If you want to make something useful from this there is really only one approach open to amateurs unless you have a very
sophisticated fractional distillation set up and that is to oxidize it to a mixture of benzene-dicarboxylic acid which can then be separated
relatively easily (I have several reference if anybody is interested). Because these acid are very resistant to further oxidation you can use insanely
aggresive conditions, eg excess hot dichromate and sulphuric acid or alkaline permanganate solutions.
If you have no use for isophthalic acid (likely, since it doesn't appear to be much use) you can partially deplete the xylene in the m-isomer by
treating it with about one third of its volume of warm conc sulphuric acid for 24 hours culminating in reflux for a while (this process was developed
from Clarke and Taylor, J Amer Chem Soc., v45 p831 (1923)). The mixture is then cooled, diluted and the organic phase separated and distilled to give
a xylene enriched in o and p isomers. I presume the aqueous liquor could be worked up for the m-xylene sulphonic acid but I don't know which position
the sulphonic acid enters, though the 4-sulphonic acid probably predominates. I never finished this work because I managed to acquire samples of the
pure isomers.
As you have probably guessed I have been researching a very similar topic for some time (years) 
|
|
|
Zyklon-A
International Hazard
Posts: 1547
Registered: 26-11-2013
Member Is Offline
Mood: Fluorine radical
|
|
Quote: Originally posted by peter80  | Im investigating the chlorination of xylene. Ive read that
sodiumchlorate + HCl results in free chlorine.
|
Are you doing this chlorination in situ? Chlorate plus strong acid makes chloric acid, which is unstable and decomposes to chlorine, chlorine dioxide
and water. Not a very good way to isolate chlorine at all, try acidifying hypochlorite or trichloroisocyanuric acid.
[Edited on 12-7-2015 by Zyklon-A]
|
|
|
CuReUS
National Hazard
Posts: 928
Registered: 9-9-2014
Member Is Offline
Mood: No Mood
|
|
I hope this helps
click the first link(chlorination of aromatic systems using TCCA)
https://www.google.co.in/?gfe_rd=cr&ei=ZZqiVcefFuLI8AeT5...
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
