PeetPb - 27-7-2013 at 14:41
Hey,
I was just wondering, could TCPO (bis(2,4,6-trichlorophenyl) oxalate) be made simply by the Fisher esterification ? that is to react trichlorophenol
with oxalic acid and H2SO4.
I guess not because I've never seen it prepared this way, but why ?
The whole point of this is to omit the use of oxalyl chloride which is much more unpleasant (and much harder to get) than oxalic acid.
Thanx
bbartlog - 27-7-2013 at 16:52
I don't think the trichlorophenol is a suitable 'alcohol' for this esterification.
Dr.Bob - 29-7-2013 at 12:38
This will not work well. Fisher esterification is best with small, simple, alcohols, where you can take advantage of equilibrium by swamping the
acid with alcohol, thus moving the reaction to the right:
Acid + alcohol <-----> Ester + water
In most cases you can use 10-100+ equivalents of alcohol, which can produce a decent yield of ester.
For trichlorophenol, this vast excess would be hard to create, plus trichlorophenol is not exactly the best nucleophile for this task. The oxalyl
chloride method is really the best way. Also be aware that heating this reaction or allowing it to overheat when running can produce chlorinated
dioxins as side products (albeit in small amounts, but they are very nasty compounds).
Also, you want to make a diester from one acid and two alcohols, which is entropically about as likely as a jig saw puzzle assembling itself as you
drop the box of pieces on the floor.
Paddywhacker - 29-7-2013 at 16:12
A few years ago somebody posted about successfully acetylating phenols by this method. I cannot be bothered chasing down the reference, but it will
be out there somewhere.
The problem that I see is that your substrate is not electronically a standard phenol. More knowledgeable posters than I might be able to hazard a
guess as to whether the mono alkyated product was likely. Additionally the bis product would have to surmount steric hinderances to form.
[Edited on 30-7-2013 by Paddywhacker]