Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Meter on January 18, 2021, 02:40:29 AM
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Hi.
I found this step in a synthesis of a certain compound and I determined that it looks a lot like the chlorination of a carboxylic acid. From what I can find, such chlorinations generally use SOCl2 (thionyl chloride) and not SO2Cl2 (sulfuryl chloride). What makes this different?
(https://i.imgur.com/kj8N8Wt.png)
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It looks strange, DMF can probably not be the solvent? Maybe its a type-error, it should be SOCl2? Also you will get the product as HCl-salt.
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It looks strange, DMF can probably not be the solvent? Maybe its a type-error, it should be SOCl2? Also you will get the product as HCl-salt.
I just realized that the article in which I found the synthesis, they do not cite a source for its synthesis pathway. Wikipedia isn't always a great source, so it could just be nonsense.
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If this diagram is from Wikipedia, there is sure to be a link citing the original publication there. Printing errors can happen anywhere.
Once you notice an error, you can correct it yourself after thoroughly checking the reference literature.
DMF is commonly used as a catalyst in the synthesis of acid chlorides with thionyl chloride.
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I think DMF is used as catalyst when oxalyl chloride is used, not thionyl chloride. It is not used as solvent?
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If this diagram is from Wikipedia, there is sure to be a link citing the original publication there. Printing errors can happen anywhere.
Once you notice an error, you can correct it yourself after thoroughly checking the reference literature.
DMF is commonly used as a catalyst in the synthesis of acid chlorides with thionyl chloride.
It doesn't seem like there is a paper attached to it.
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A slightly tangential comment: It has been some time since I worked with SO2Cl2, but I used to distill it away from a lower boiling impurity shortly before use.
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DMF is perfectly fine to be a solvent. Why wouldn't it be? I'm more concerned about that amine there either reacting with the acid chloride or this thing precipitating out when protonated.
BTW its common to run chlorinations in neat thionyl chloride, sometimes with a drop of catalytic DMF.
Workup is either distill off thionyl chloride, or if the product is kinda water stable, dump it into ice then extract with water and organic solvent.
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Wildfyr, I think acid chlorides react with DMF much like POCl3 does when you make Wilsmeyers reagent.
I have never seen DMF used as catalyst when making acid chlorides with SOCl2 but often when oxalyl chloride is used.
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Hm... I think i've used those conditions for SO3Na --->SO2Cl
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Wildfyr,I can be wrong, I dont have any reference to support this, its more from experience.
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US1326040A - 1919
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AWK, what does the patent say, I can not find it on the web?
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https://patents.google.com/patent/US1326040A/en
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Thanks AWK. I dont see anything about DMF but its a lot if text, have I missed it?
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There is no mention of DMF, but the reaction concerns the preparation of acid chlorides and anhydrides by the action of SO2 + Cl2 on carboxylic acid salts, and the products may be acid chlorides or anhydrides depending on the proportion of reactants. The salts are wetted with ethyl acetate before reaction.
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I dont understand how this is relevant for the question from Meter?
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It all started with the question (which is in the title of the thread) whether SO2Cl2 can be used to synthesize acid chlorides. Meter showed a reaction that also includes DMF (he claims the reaction is from Wikipedia).
You started a discussion about the advisability of using DMF, and then the discussion went sidetrack.
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Thats true. I think many reagents can be used to make acyl halides, including SO2Cl2. It looked as if they used DMF as solvent and that seems strange to me.
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I've personally always used thionyl chloride, and its pretty much failsafe. Its more of a hassle to handle and get rid of than oxalyl chloride, but its also probably a more powerful chlorinating reagent. A "drop" of DMF was always suggested to me for making acyl chlorides or sulfonyl chlorides, but I never really compared with/without the DMF.
I've usually chlorinated in neat thionyl chloride, but sometimes done 1 eq in a solvent like DCM. When doing that I actually probably leave out the DMF. No accounting for my decision :P
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Yes thionyl chloride is good, for benzoic type acids reflux can be used, not nessecary with aliphatic acids I think.