Can be alizarin produced by Friedel-Crafts reaction of phtalic anhydride and catechol? What should be used as catalyst? ZnCl2 or conc. H2SO4 (with
H2SO4 will be easier to work)? Can be alizarin used for production of dihydroxybenzanthrone by reaction with glycerol and copper. Thank you very much
for help.unionised - 23-4-2016 at 09:10
"Can be alizarin produced by Friedel-Crafts reaction of phtalic anhydride and catechol?"
Maybe, but if you do the reaction in the presence of sulphuric acid you get something else
Nope. FC-acylation and phenols don't play nice. Even if the phenols were protected as ethers, the 2,3-product would probably dominate the reaction
products.
While alizarin is regarded as the first synthetic version of a natural pigment, my reading on the subject showed that this is a bit of a stretch. The
"alizarin" was produced by bromination of anthraquinone under pressure followed by fusion with alkali hydroxides. This produced a mixture of
polyhydroxyanthraquinones, not merely 1,2-dihydroxyanthraquinone. Functionally it dyed fabric in a similar manner but possibly with different
light-fastness and color shade.
An improved prep starts with anthraquinone, sulfonates it with oleum, and isolates sodium anthraquinone-2-sulfonate (Silver salt). On fusion with
alkali hydroxide and nitrate, alizarin is produced. I can't find my reference paper for this synthesis however.
It can also be made from o-dichlorobenzene and phthalic anhydride. On fusion with alkali, the 2,3-dichloroanthraquinone dehalogenates and rearranges
to alizarin.
I am also attaching a prep of radiolabelled alizarin. While most of the prep is impractical as a reasonable alizarin synthesis, the last step is an
oxidation of 2-hydroxyanthraquinone to alizarin using alkali and chlorate that may prove useful.
[Edited on 23-4-2016 by UC235]Boffis - 23-4-2016 at 13:04
You don't need a FC reaction; Phthalic anhydride and catachol react in conc. sulphuric acid but the main products are tars, hydroxyphenylxanthines and
2,3-dihydroxyanthroquinone, only a little 1,2-dihydroxyanthraquinone is produced. It is described in an old book I have on anthraquinone dyes but I
don't have it with me so I can't give you a reference but the reaction was described under the 2,3 dihydroxy compound as the original method of
preparation of this compound. The seperation is tedious though and the total yield of both compounds poor.morsagh - 23-4-2016 at 13:58
Are there any conditions like refluxing Boffis? Sounds interesting, I´ll try it.CuReUS - 24-4-2016 at 02:21
there is another method from pthaloyl chloride and catecol
"Sartori, Giovanni; Casnati, Giuseppe; Bigi, Franca; Foglio, Federica Gazzetta Chimica Italiana, 1990 , vol. 120, # 1 p. 13 - 19"morsagh - 25-4-2016 at 11:30
Product after reacting catechol and phthalanhydride in conc. sulphuric acid. Do you think it is mostly 1,2 dihydroxyantraquinone or 2,3?
Pumukli - 26-4-2016 at 09:14
Dunno, I'd prefer it would be the 1,2-dihydroxy variety. :-)
Anyway, if you want less uncertainty but a similar nice dye then you should start from hydrochinone instead of catechol. This way the reaction should
yield purpurin, which is the 1,4-dihydroxy compound.
If you had the 1,2-dihydroxy compound (alizarin) then you could nitrate it and the nitro group should move to position 3. The resulting compound is
alizarin orange and it has (or so they say) a nice orange color. :-)Boffis - 26-4-2016 at 17:53
@Morsagh
I have found a reference to the sulphuric acid condensation that is exactly what I described above: check out Berichte 1888 v21 p2503. A Schoeller. He
used 5g of catechol and 6.5g of phthalic anhydride in 75g of conc sulphuric acid for 4.5 hours at 140-145 deg C. He goes on to describe the work up.
Also worth a look is:
Berichte v28 p116; K Lazodzinski 1895; FC condensation in carbon disulphide; phthalic anhydride + dimethyl ethers of dihydroxyphenols to the
appropriate dimethoxyanthraquinone (veratrole gives mainly 2,3-methoxyanthraquinone and by hydrolysis of the ether hystazarin or
2,3-dihydroxyanthraquinone). Also covers the condensation of hydroquinone dimethyl ether to give ultimately Quinizarin
Another ref (Berichte v35 p1778) found that prolonged digestion of hystazarin in conc sulphuric acid results in partial convertion to alizarin. This
may explain the alizarin found by Schoeller.morsagh - 27-4-2016 at 10:17
I will try next time that with hydroquinone, don´t you know how to extract purpurine and how to extract alizarin/nitroalizarin? Pumukli - 27-4-2016 at 12:20
Corrections to my previous comment in this thread:
1,4-dihydroxy-anthraquinone is NOT purpurin. It is called quinizarin. Purpurin is a derivative of quinizarin, it is 1,2,4-trihydroxy-anthraquinone. (I
mixed up the common names, sorry.)
The industrial quinizarin synthesis starts from p-chloro-phenol instead of hydrochinone. Starting from the later is possible too, but requires working
with molten AlCl3/NaCl mixture and the yield is still very low. :-(
P-chloro-phenol is condensed with phthalic anhydride with H2SO4 and boric acid. Boric acid continuously removes the forming
quinizarin by esterification from the mixture and turns the equilibrium reaction into a one-way route.
You can read about anthraquinone dye chemistry here:
Bien, H.-S.; Stawitz, J.; Wunderlich, K. (2005), "Anthraquinone Dyes and Intermediates", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim:
Wiley-VCH, doi:10.1002/14356007.a02_355
