Halogenation of xylene

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)

Quote: Originally posted by peter80

Im investigating the chlorination of xylene. Ive read that sodiumchlorate + HCl results in free chlorine.