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Author: Subject: Lewis acid for benzophenone synthesis with benzoyl bromide
Number 9
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[*] posted on 26-6-2012 at 06:01
Lewis acid for benzophenone synthesis with benzoyl bromide


In occassion, the preparation of 2-chloro-5-nitrobenzophenone is the reaction of benzoyl chloride with 4-nitro chlororbenzene. The last compound can be made only by following the instructions given in the book Chemie und Technologie der Explosivstoffe, Tadeusz Urbanski (1964). Volume 3.

But that's not my question. I know that phosphorus tribromide can be made by the reaction of bromine (pure), which can be solved in dichloromethane. This product can react with white or red phosphorus in that solvent. It react fast with water in the air but it reacts with e.a. propionic acid to give propanoyl bromide. Observed boiling point 80°C (1 atm) This is also reactive with water in the air.

But now there is a problem. Aluminiumbromide didn't work to make a derivate with toluene. It forms a sticky, black compound and there was no reaction at all.

So, what Lewis acid is suitable for these kind of reactions and how perform it? I don't find any scientific references.

Note:
- Preparation of phosphorus pentachloride isn't possible in the lab since chlorine don't solve in dichloromethane and is a strong poison and very dangerous to handle. (respiratory system)
- Benzoyl chloride or thionyl chloride or phosphorus pentachloride are not available at this moment. That's no option.

[Edited on 26-6-2012 by Number 9]
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Nicodem
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[*] posted on 26-6-2012 at 07:22


Quote: Originally posted by Number 9  
In occassion, the preparation of 2-chloro-5-nitrobenzophenone is the reaction of benzoyl chloride with 4-nitro chlororbenzene.

What? You have a reference for a reaction that is by all means considered impossible? Please give us the reference!
Obviously, without checking that reference it is impossible for anyone here to give you any useful advice. We are talking about a Friedel-Crafts acylation of a substrate that is even less activated than nitrobenzene (which is otherwise considered the borderline substrate for any FC reaction).
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It forms a sticky, black compound and there was no reaction at all.

That is a very beautiful oxymoronic sentence. I will add it to my collection.




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kavu
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[*] posted on 26-6-2012 at 07:27


As Nicodem stated the reaction will not proceed in such a way. If you want to synthesize 2-chloro-5-nitrobenzophenone you will have to go the other way round an start with 2-chloro-5-nitrobenzoyl chloride and do a FC with benzene. This synthesis has been published as early as 1898 in Chemische Berichte.
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[*] posted on 29-6-2012 at 09:16


My reference is http://www.sciencedirect.com/science/article/pii/S1878535211... (Rajesh K. Singh, Sonia Devi, D.N. Prasad (2011). Synthesis, physicochemical and biological evaluation of 2-amino-5-chlorobenzophenone derivatives as potent skeletal muscle relaxants. Arabian Journal of Chemistry)

But they use no paranitro chlorobenzene, but 4-amino-chlorobenzene to perform a FC acylation at 220°C-230°C and ZnCl2 as Lewis base.

Can I trust this information?

As far as I know, the amino group is a strong activator and is a ortho, para - activator. Since the para-group is already occupied by -Cl, there are only 2 ortho-groups to react with. But, it seems more likely that this reaction fails because:
- very high temperatures (oxidation products of parachloroaniline and other things)
- very high reactivity of benzoyl chloride with the amino-group

So, what is your opinion about this reaction?

[Edited on 29-6-2012 by Number 9]
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Nicodem
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[*] posted on 29-6-2012 at 23:20


Quote: Originally posted by Number 9  
My reference is http://www.sciencedirect.com/science/article/pii/S1878535211... (Rajesh K. Singh, Sonia Devi, D.N. Prasad (2011). Synthesis, physicochemical and biological evaluation of 2-amino-5-chlorobenzophenone derivatives as potent skeletal muscle relaxants. Arabian Journal of Chemistry)

But they use no paranitro chlorobenzene, but 4-amino-chlorobenzene to perform a FC acylation at 220°C-230°C and ZnCl2 as Lewis base.

So, essentially you made up the information about the Friedel-Crafts reaction between p-nitrochlorobenzene and benzoyl chloride? And you wanted us to suggest you a catalyst for an impossible reaction? You have a strange sense of humor which I do not like.
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Can I trust this information?

...

So, what is your opinion about this reaction?

Why asking us? What use would you have from an opinion? Either check the literature or check the experiment. In either case you will have to do some literature work, because those Indian authors did not bother giving the reference. I suggest you, to either visit a library, or send them an email requesting the reference for that reaction.




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chemrox
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[*] posted on 30-6-2012 at 16:53


The journal you cited is not peer-reviewed in any meaningful way. The only procedures I know to be consistently reliable are the ones in Organic Syntheses. All the procedures are checked by other chemists before they are published. Other pubs have varying degrees of integrity with Indian and Arabian journals ranking pretty low.

[Edited on 1-7-2012 by chemrox]




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