Sauron
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A Twofer Prep - Two Acyl Chlorinating Reagents Made at One Step
Phthaloyl chloride and benzoyl chloride are the only products and in near quantitative yields when phthalic anhydride and benzotrichloride are reacted
at 110-120 C for 20 hours in presence of ZnCl2 catalyst.
225 g phthalic anhydride
295 g benzotrichloride
20 g ZnCl2
After 20 hours at 110-120 C product is carefully fractionated in vacuo
Obtained
208 g benzoyl chloride bp 9095/23mm (100% of theoretical)
8.8 g middle cut up to 138 C/23mm
287 g phthaloyl chloride bp mostly 150-152 C/23mm
The phthaloyl chloride contains some dissolved phthalic anhydride which can be partially removed by fractional crystallization. This material does not
interfere with the reagent in most instances.
The ZnCl2 remains in the pot and can be reused in subsequent runs.
Both of these reagents are useful in preparing acyl chlorides more volatile than themselves. Benzoyl chloride works well for preparation of acyl
chlorides boiling up at c.150 C. It is employed in 50-100% molar excess. See H.C.Brown's article in JACS.
Kyrides' article on phthaloyl chloride is attached.
These reagents work well for lower acyl chlorides for which traditional chlorinating reagents such as thionyl chloride fail due to difficulty in
seperating the excess reagent from the product. The same objection applies to PCl3, POCl3 and PCl5, particularly for C2-C4 acyl chlorides.
The starting materials are a lot easier to obtain than those traditional reagents these days.
Attachment: Kyrides_phthaloyl.pdf (318kB)
This file has been downloaded 688 times
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garage chemist
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Nice!
I want to add that a modification of this process exists, where benzotrichloride is reacted with benzoic acid in presence of ZnCl2 and benzoyl
chloride is the only product. A patent for making acyl chlorides from benzotrichloride has been posted here once, the thread had been started by me.
It seems like acetyl chloride can be a product as well if acetic acid is used instead of benzoic acid. Also, benzal chloride can be used in place of
benzotrichloride.
https://sciencemadness.org/talk/viewthread.php?tid=3933&...
Some people here seem to prefer extracting phthalates from latex gloves to make phthalic acid, which cannot be considered a viable source of this
compound. Hence the modification of using benzoic acid should be useful.
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not_important
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| Quote: | | Some people here seem to prefer extracting phthalates from latex gloves to make phthalic acid, |
Shower curtains is the most recent source. Cheap children's toys is another, the soft vinyl ones. Find them left outside the house when a family moves
and discards all the things outgrown or well dented and dinged; collect and leave out one winter's night, then grind them up while they're cold and
stiff, and extract with acetone.
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garage chemist
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How do you know they dont contain other esters as well, like sebacates, terephthalates etc...? Do you even measure the melting point of your product?
I find that source of phthalic acid really stupid to be honest, its like making rust from steel wool. Are some people here really too lazy to go to
the pharmacy to order a compound that is 100% non-watched and cant cause them any problems at all? Phthalic acid or anhydride has lots of very
interesting uses, like making fluorescein, its something worth spending a little money on to have a pure product.
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not_important
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Care to list those OTC sources, and see how many people can find them? In some areas a product may not be available, be it from the formulations use
by the major manufactures there or from legal restrictions. I've lived in places were I could buy a half liter of methyl salicylate, as "synthetic
oil of wintergreen", at the dry goods store, and in other places where it was prescription only, and one were it was not to be found except in a few
obscure ethnic shops.
And, yes, I did check purities of product. The extraction and hydrolysis is only a starting point. Phthalates are the most common by far, adipates
next, citrates in some films, epoxidised vegetable oils and chlorocarbons are used as secondary plasticisers. Adipates have higher migration rates and
higher volatility than phthalates, as well as a bit higher costs. Terephthalates don't show up, sebacates and azelates are too expensive to be used in
low end consumer items. Phosphates seem to be limited to flame-proofing usage, I've not run into them in cheap consumer stuff. The citrates tend to
be used in food films and medical goods. Solubility of the free acids is a starting point of separation, the made in China toys mostly seem to use
phthalates and hydrocarbons and chlorohydrocarbons, so the separation in those cases is pretty simple. Some had adipates in them as well, which is
more difficult to separate, but going to the anhydrides allows that to be done and it's the anhydride that's most useful.
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tito-o-mac
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Shouldn't we use a gas mask in such experiments?
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Sauron
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No gas mask needed as no gas (HCl) is liberated.
@GC, the fly in the ointment with making benzoyl chloride per se out of benzotrichloride is that benzotrichloride is more expensive than benzoyl
chloride.
1 liter benzotrtichloride 1380 g $54
1 liter benzoyl chloride 1210 g $30
Those are ex works Acros prices and by the time you have these in hand the cost will have doubled (it does for me anyway).
When you react benzoic acid with benzotrichloride one mol to one mol, one of the chlorines is "wasted" as HCl, one chlorinates the acid and one
remains on the now oxidized methyl (now carbonyl) carbon.
In other words it is cheaper to just buy the benzoyl chloride than to make it that way
Assuming yields are high then you do get 2 mols benzotrichloride. But the costs still don't favor this reaction unless you are getting your benzoic
acid for free.
Phthaloyl chloride is very costly to buy (quite a bit costlier than benzotrichloride) and has unique reactivity that benzoyl chloride lacks.
1. The ability to make cyclic anhydrides in certain instances
2. The ability to make SOCl2 from SO2
3. IIRC the ability to chlorinate oxalic acid (an ability shared only by PCl5 and TCT)
So assuming that you want or need phthaloyl chloride it does save a lot of money to make it, and getting benzoyl chloride in the bargain effectively
for nothing helps a lot.
Was the patent you were talking about the US patent issued to Monsanto and cited by Kyrides in the JACS article?
[Edited on 4-7-2007 by Sauron]
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benzylchloride1
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Something that may be of interest that I found while browsing Weygand and Hilgetag's Preparative Organic Chemistry, page 272.
Phthalic thioanhydride, for example, is readily obtained from phthalic anhydride and
Na2S,1289 and when Cl2 is led through this material molten at 245° until SC12 is no longer
formed, phthaloyl chloride is obtained in almost quantitative yield.1290
References:
1289 A. Reissert and H. Holle, Ber. Deut. Chem. Ges., 44, 3029 (1911).
1290 E. Ott, A. Langenohl, and W. Zerweck, Ber. Deut. Chem. Ges., 70, 2360 (1937).
Amateur NMR spectroscopist
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