I am about to prepare a large batch of luminol. Unfortunately my phthalic anhydride hasbeen partly degraded to phthalic acid. Does anyone know if
phthalic acid can be nitrated in the same conditions as the anhydride (not requiring fuming acids) giving the same or better ratio of 3-isomer? I have
been looking for references but can't find a good answer.
I can also heat and sublime or heat with xylene to get the phthalic anhydride but I'd rather don't.#maverick# - 21-7-2011 at 17:56
Nurdrage has a bid and he just heats the phallic acid to 300 c with a flask of cold water over the beaker and the pthalic anyhydride deposits on the
sides like Cotten candy a d u just collect it. I'm in the process of tryig to get diethylhexyl pthalate from gloves then converting to pthalic acid it
just won't work even though I used the sane method as nurdrage I'm starting to think the diethylhexyl phtalate was not used as the plasticizer in
these gloveshkparker - 21-7-2011 at 18:49
I'm not sure Jor but the lack of documentation makes me think you should dehydrate it. I know UnintentionalChaos has used xylene before but what
would your procedure be? Im not sure how that works but I know he used a dean stark trap.UnintentionalChaos - 21-7-2011 at 20:12
Fuming acids are unnecessary. We have a large thread on 3-nitrophthalic acid already with a number of excellent references. I was quite successful
with azeotropic HNO3 (or rather concentrated HNO3 diluted to azeotropic strength) and concentrated sulfuric acid. Don't expect a high yield. if you
assume that conversion to the 3 and 4 isomers is 50:50 (which it isn't), max yield is 50% for the desired isomer. I got reasonably pure 3-isomer in
35% yield.
I'm not sure Jor but the lack of documentation makes me think you should dehydrate it. I know UnintentionalChaos has used xylene before but what
would your procedure be? Im not sure how that works but I know he used a dean stark trap.
I placed a dean stark trap on top of a 1-neck 500ml RB flask containing the phthalic acid. I used a Friedrich condenser on top the the dean stark, but
any good condenser should work.
the dean stark was filled with xylene just a little short of the spill-over point and the lower flask heated until the phthalic acid began to melt and
dehydrate. Water comes up the neck of the dean stark and runs into the reciever. A little phthalic anhydride comes over as well, but not much. The
xylene starts to spill over shortly and the distillate becomes milky from condensing azeotrope. Water continues coming over for a while.
I did not drain water from the dean stark but I was only expecting ~4ml of water to come over displacing ~3ml of xylene into the stillpot and
condenser. There was probably no liquid xylene in the stillpot to drive down the temperature as might be a concern with larger batches. In that case,
I'd remove water from the trap mid-procedure so less xylene is outside the trap.
Eventually the condensate stays clear, at which point, you are done. Once cooled and frozen, I added more xylene to the product (benzene or toluene
would have been better because the xylene is difficult to remove from the product due to it's high boiling point), the mix was heated until homogenous
and allowed to cool slowly, forming crystals of phthalic anhydride. These are filtered off. The melting point agreed with that of an authentic sample.
Loss can be minimized by stirring the xylene with hot NaOH solution or similar to remove the phthalic anhydride as disodium phthalate and recycling to
phthalic acid.
[Edited on 7-22-11 by UnintentionalChaos]hkparker - 21-7-2011 at 21:07
@UnintentionalChoas Does the xylene extraction give better yields then NurdRage's decomp method? Also as Jor said do you know if we can just nitrate
phthalic acid, not the anhydride?
