jayhouse
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propionyl chloridd
Hi guys.
Anybody know what is the equivalent of propionic acid and benzoyl chloride? I'm told that you can make propionyl chloride by mixing equivalent of
these two and then distill off the propionyl chloride. But, i dont really know what amount of each should i mix in order to distill properly the
propionyl chloride. Please help. Thanks..
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Chemosynthesis
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If this is a serious question, you definitely need to look into general chemistry a bit more, or give us more information if I am misunderstanding
you.
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jayhouse
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Yes it is. I read in a forum that by mixing propionic acid and bezoyl chloride, you can get propionyl chloride by distilling it off. But they also
mentioned that it is equivalent of each. So what is the amount of eahc to be mixed? Thats really my question.
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woelen
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You need to mix them in a 1 : 1 molar ratio. I foresee some complications in distilling off the propionyl chloride, because you get formation of
benzoic acid, which will form a slurry of solid material, wetted with the propionyl chloride and unreacted propionic acid and benzoyl chloride.
If this is something you do not understand, then I first would take some time to study the basics of chemistry, before "playing" with chemicals like
benzoyl chloride. The end product, propionyl chloride is nearly as nasty as benzoyl chloride and must be treated with great care!
Do you really understand the risks of such nasties as the acyl chlorides? These are not the easiest to handle and can do a lot of harm if not treated
properly.
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Darkstar
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Quote: Originally posted by woelen  | If this is something you do not understand, then I first would take some time to study the basics of chemistry, before "playing" with chemicals like
benzoyl chloride. The end product, propionyl chloride is nearly as nasty as benzoyl chloride and must be treated with great care!
Do you really understand the risks of such nasties as the acyl chlorides? These are not the easiest to handle and can do a lot of harm if not treated
properly. |
Exactly. If you're having trouble understanding simple stoichiometry, then you should probably take the time to at least learn some basic chemistry
before attempting to handle/synthesize acyl chlorides. With that said, if you're still intent on making propionyl chloride using benzoyl chloride, you
might find this helpful.
Good luck and stay safe.
[Edited on 11-12-2014 by Darkstar]
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forgottenpassword
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It is not a matter of "simple stoichiometry". As can be seen in that paper, maximum yield is obtained if non-stoichiometric ammounts are used. It is
wrong to assume that someone is completely ignorant just because they want more information on a particular reaction, and to learn from the
experiments that others have done to determine optimum ratios of reactants. For preparatively useful reactions, it is very rare that stoichiometric
ratios will give optimum yields. In fact it is good indicator of inexperience if someone imagines that it will! In this instance, 1:1 gives 63%,
whereas 3:2 (chloride:acid) gives 84%. You can see, consistently, in the optimization experiments, a stoichiometric ratio is NOT* the one to use.
*Although, to do a complete U-turn, maybe it IS! WIth such simple reactants, economics may come into the equation. Benzoyl chloride, being more
expensive than propionic acid, should be as efficiently utilized as possible. In this case it would involve accepting a smaller yield of the product
to gain maximum utilization of the benzoyl chloride. I should have just kept quiet!
[Edited on 11-12-2014 by forgottenpassword]
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Darkstar
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Yes, I understand that. I even considered pointing out that, according to the paper, non-stoichiometric amounts actually gave the better yields. The
reason I assumed ignorance was because his question--at least to me--came off as, "what does an equivalent amount of propionic acid and benzoyl
chloride mean?" It means a 1:1 molar ratio. Pretty basic stuff. I didn't see his question as, "what is the optimal ratio of propionic acid to benzoyl
chloride?" My intent, like woelen, was to warn him of the potential dangers of working with acyl chlorides in the event that he is ignorant.
I did not mean to insult or offend him and I apologize if I misunderstood his question.
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Bert
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Thread Moved
11-12-2014 at 03:57 |
forgottenpassword
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You may be right, actually. If he comes back with "what does 3:2 equivalents mean?" we'll know for sure!
On the practical side of things, it is clear from that paper that a fractionating column and very careful fractionation, and refractionation, is
required to obtain a pure substance. Coupled with the water sensitivity of the distillate, this is by no means a simple preparation, even though at
first glance it appears to be. Some previous experience of fractional distillation in an inert atmosphere would be very helpful. Even then, the
volatilizing influence of the liberated HCl (as mentioned in the paper) will complicate matters, and a high reflux ratio must be maintained.
[Edited on 11-12-2014 by forgottenpassword]
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woelen
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I agree with Darkstar. I did not study this reaction, but as you can infer from my reply, I did not expect a 100% yield (I mention unreacted input
reactants), but I do expect lots of complications in the reaction. My post was just intended as a warning to the OP. My experience with forums is that
the way the question is formulated indicates lack of knownledge and understanding, and combining that with the handling of acyl chlorides in somewhat
larger quantities may lead to personal disaster!
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Chemosynthesis
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This is exactly why I was hoping the OP would come back and explain a little more about what was confusing them. I wasn't sure if they were even aware
of the differences between theory and lab practice, or equilibria.
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Bert
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When first this appeared, I suspected it was another of the trolling posts.
The possibility that someone would be contemplating such a synthesis and not know what "equivalent" meant in that context?
Since then, not so sure. My own quick look into the chemistry kept ending up at Rhodium, Erowid, opiophile & etc.
http://forum.opiophile.org/archive/index.php/t-6143.html
I will defer to Woelen, Nicodem etc. on shifting this to detritus. Not really my strong area.
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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unionised
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| Quote: Originally posted by woelen | You need to mix them in a 1 : 1 molar ratio. I foresee some complications in distilling off the propionyl chloride, because you get formation of
benzoic acid, which will form a slurry of solid material, wetted with the propionyl chloride and unreacted propionic acid and benzoyl chloride.
If this is something you do not understand, then I first would take some time to study the basics of chemistry, before "playing" with chemicals like
benzoyl chloride. The end product, propionyl chloride is nearly as nasty as benzoyl chloride and must be treated with great care!
Do you really understand the risks of such nasties as the acyl chlorides? These are not the easiest to handle and can do a lot of harm if not treated
properly. |
I'm not sure whether you are more wrong because the melting point of benzoic acid is lower than the boiling points of most of the other components, or
because it will dissolve.
As you say
"If this is something you do not understand, then I first would take some time to study the basics of chemistry, before "playing" "
It's not that I don't know that you know better than that; it's just that you need to be a bit more careful about what you post.
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woelen
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I think I was a little unclear in my post. The word "this" at the start of the second section (If this is something . . .) refers to the remark made
by the OP and not to the possibility of formation of solid matter.
But before we get a lot of discussion on wording and what we should say or not, let's wait and see what the OP has to add to this. I hope he gets the
main message of what I (and a few others) wanted to say. If the OP does not return to this, then for me the discussion has ended.
Of course, if others want to continue, it is their good right to do so.
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chemrox
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preparation of propionyl chloride
Actually Brown tried several ratios and using a 2:1 excess of benzoyl chloride seemed to produce better yields. I'll post the paper later I'm in a
power outage.
Attachment: 79720443-Brown, Herbert C.-A-Convenient-Preparation-of-Volatile-Acid-Chlorides.pdf (439kB)
This file has been downloaded 390 times
[Edited on 12-12-2014 by chemrox]
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Scr0t
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Preparation of propionyl chloride
Propionyl chloride was prepared via benzoyl chloride and propionic acid based upon the method described in Brown's article above. A 1:1 molar ratio of
reactants was chosen to give a better yield based upon the more expensive benzoyl chloride.
In a 500ml flask (200.7g, >=98.5%) benzoyl chloride and (104.1g, >=99.5%) propionic acid (~1:1 molar ratio) were combined and setup in an oil
bath for vertical distillation through a 200mm Vigreux column and coil condenser with magnetic stirring.
The oil bath was heated ultimately to 190'C to provide 71.3g of distillate that was collected over 45-69'C (most over 64-69'C) while a stream of HCl
gas was vented from the reaction to give a yield of ~54% propionyl chloride.
The receiver flask was changed and a mild vacuum was carefully applied to flash distill ~20g of liquid. On re-distillation of this liquid about 7g of
propionyl chloride was obtained bringing the yield to ~59% [1].
The remaining liquid in the distillation flask was a pale yellow/brown and on cooling formed a crystalline mass of benzoic acid with some liquid
present.
[1] The article claims a yield of 63% for this ratio.
There was a claim of this reaction for acetyl chloride that required ZnCl2 to proceed from versuchschemie.
https://www.sciencemadness.org/whisper/viewthread.php?tid=10...
Such is not the case with propionyl chloride at least.
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