Finechem
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Pthaloyl chloride from Thionyl
why not make Pthaloyl Chloride by reacting Pthalic Anhydride and Thionyl. This is better than producing Benzoyl Chloride which can be prepared from
Sodium Benzoate.
Hence you get both the products without carrying the distillation.
ChoW
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Sauron
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Read the article (posted on this forum already by Thomas Kyrides of Monsanto, from JACS and you will have your answers.
1. Thionyl chloride fails to chlorinate phthalic anhydride under usual conditions.
2. In many places thionyl chloride is hard to buy, restricted or prohibited as a precusrsor to a chemical weapon. This is a consequence of Iran and
Iraq having bought so much of it during the 1980s.
3. The best prep of phthaloyl chloride is from benzotrichloride and phthalic anhydride, you get a quantitative yield of phthaloyl chloride and also a
quant yield of byproduct benzoyl chloride.
4. If you look up the price of sodium benzoate and that oif benzoyl chloride you will see they are the same, so making one out of the other is stupid
economically. There is a cheaper way to make this but it requires TCT and thst is hard to get in Europe and I tire of having our European members
kvetch when I post about it.
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Sauron
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Here is the JACS article by L.Kyrides of Monsanto.
To summarize, PCl5 will chlorinate phthalic anhydride.
SOCl2 will dehydrate phthalic acid to the anhydride but will not chlorinate either the acid or the anhydride at reflux temperature (c.80 C) even in
presence of pyridine.
SOCl2 will however chlorinate phthalic anhydride at elevated temperatures and pressure in presence of anhydrous ZnCl2. This reaction is reversible, so
phthaloyl chloride and ZnCl2 will react with dry SO2 to give SOCl2.
Furthermore, phthalic andhydride and benzotrichloride with ZnCl2 catalyst gives a quantitative yield of phthaloyl chloride and benzoyl chloride.
Phthaloyl chloride is a useful chlorinating reagent for acyl chlorides.
[Edited on 28-7-2007 by Sauron]
Attachment: Kyrides_phthaloyl.pdf (318kB)
This file has been downloaded 466 times
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Ozone
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Phthalic anhydride is thermodynamically very stable. It is not even hygroscopic. Reactions with it invariably seem to require catalysis (ring opening
via direct addition of a nucleophile, for example.)
Cheers,
O3
[Edited on 29-7-2007 by Ozone]
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Sauron
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Surely it would be more commonly used except for two factors.
It is a little expensive to buy
And preparing it requires an autoclave (pressure reactor).
This lets a lot of people out, but, luckily I have a Parr stirred and heated SS316 reactor so I can make this stuff on a reasonable batch scale. The
working capacity of the vessel is 660 ml so I can replicate the prep in Kyrides' JACS paper directly.
In fact I have ordered benzotrichloride so I can try this. Plenty of phthalic anhydride on hand and locally available. ZnCl2 on hand.
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