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Author: Subject: One pot electrosynthesis chloroacetic acid from ethanol and salt
Hexabromobenzene
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[*] posted on 15-1-2025 at 02:45
One pot electrosynthesis chloroacetic acid from ethanol and salt


Recently an article on electrochemical chlorination of ethanol was found
At low temperatures the main product of chlorination is acetal chloroacetaldehyde. Only at 70 degrees dichloroacetaldehyde is formed
Also during pauses in electrolysis and diluted salt solution a lot of chloroacetic acid is obtained

In theory the process can be changed to obtain chloroacetic acid. We need to take so much salt that all the chlorine reacts with ethanol. We also need a acid(sulfuric, phoshporic to maintain Ph better in an acidic after sodium chloride gives up its chlorine and becomes hydroxide.
We will also need excess current to oxidize the remaining ethanol.
A very promising process. Chloroacetaldehyde can also be used to synthesize pyrazine
https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433...
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[*] posted on 15-1-2025 at 02:49


This synthesis will be extremely cheap and easy. And even a 10% yield is acceptable.
I think in an acidic environment you do not even need a diaphragm. Chloracetaldehyde will not be reduced for example on a nickel cathode

And so alcohol, sulfuric acid or phosphoric and salt. As well as carbon electrodes. All you need for synthesis

It is necessary to conduct electrolysis at low current density to reduce heat

The synthesis of dichloroacetic acid is also possible, and DCM can be obtained from it

[Edited on 15-1-2025 by Hexabromobenzene]
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[*] posted on 15-1-2025 at 05:59


Chloroacetic acid is a very useful chemical, so that sounds promising. The acid chloride of it is also quite useful, but nasty to work with, the acid is not bad at all, compared to some chloro compounds. Used in making about a dozen common drugs, I believe.
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[*] posted on 20-1-2025 at 00:42


I did it once, but I didn't knew what I was doing or rather, had no specific goal. I used a divided cell and the reaction was on the anode chamber, it got warm and after a while there was layer separation . the smell quickly chaged from EtOH to something sweet with a tinge of the typical HCl. never repeated, nor conducted analysis of any kind.



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[*] posted on 20-1-2025 at 18:55


Quote: Originally posted by khlor  
I did it once, but I didn't knew what I was doing or rather, had no specific goal. I used a divided cell and the reaction was on the anode chamber, it got warm and after a while there was layer separation . the smell quickly chaged from EtOH to something sweet with a tinge of the typical HCl. never repeated, nor conducted analysis of any kind.

Its chloroacetaldehyde acetals.
Quote:

Further chlorination of each of these compounds leads to the
formation of trichloroethyl ether, chlorination of monochloroacetal
occurring either before or after its conversion into a chloro-ether
by the hydrogen chloride, now present in great excess
At this stage the liquid separates into an upper layer, consisting chiefly of a saturated solution of hydrogen chloride in water, and a lower layer of trichloroethyl ether. On warming, the two layers disappear and the liquid again becomes homogeneous, the t,richloro- ether reacting with the water of the upper layer and forming dichloroacetaldehyde alcoholate


Quote:

litre of 97 per cent. alcohol was allowed to drop through a capillary down the tube packed with beads previously described at the rate of about 1 C.C. in 5 minutes. Neither the tube nor the collecting flask was cooled, and a sufficient current of chlorine was maintained for it to escape freely from the exit. The alcohol was thus subjected to the action of excess of chlorine for a considerable period at a temperature not far removed from t'he ordinary. 998 Grams of a nearly colourless, fuming liquid, separated into two layers, collected in the receiver. The upper layer (diP 1-11), which consisted largely of water, weighed 582 grams and the lower layer (cl:? 2-22) weighed 416 grams. To the mixed layers a saturated solution of potassium carbonate was added unt8ilthe free hydro- chloric acid was neutralised. The liquid now separated into two layers, a lower layer consisting of a strong solution of potassium chloride and an upper, oily layer of a pale yellow colour giving off vapours which had a very irritating effect on the eyes. The pale yellow, oily liquid (di6-1-2) weighed 433 grams. It could not be separated into its constituents by fractionation. On heating, a comiderable amount distilled over in the neighbourhood of 92" he temperature then rose rapidly to about 150°, when almost complete decomposition and charring of the remainder, a large part of the whole, occurred. The liquid distilling in the neighbourhood of 92", which appeared to be a mixture of impure monochloroacet- aldehyde alcoholate with some di- and tri-chloroether and a small quantity of monochloroacetaldehyde, could not itself be separated into its constituents, as on refractionation it decomposed with much frothing. As no pure product could be isolated by fractionally distilling the oily product, either under the ordinary or reduced pressure, a further quantity, prepared as above, was added to a n equal weight of alcohol together with an excess of powdered chalk and the mixture heated to boiling for 8 hours. The product was then filtered and poured into water, when an oily liquid separated as a lower layer. This was washed with a little water, dried over calcium chloride, and fractionally distilled. It was thus separated into two main fract'ions boiling constantly a t 155" and 182", respec- tively, which analysis showed to be monochloroacetal (Found : C1 = 23.77. Calc., C1 = 23.24 per cent.), and dichloroacetal (Found : (21 = 38.11. ~ Calc., C1 = 37-92 per cent.



On the other hand, we can get monochlorinated product.

Quote:

With the object of making the manner of the progress of chlorination and oxidation clear by tracing substances formed at each stage of the reactions, electrolysis was carried out with a limited quantity of electric current, and the substances thus formed were studied. In the first experiment 50 cc. of alcohol were taken, and the electrolysis was conducted at 40°-50° by passing electric currents of 46-05 amp. hours just sufficient to complete the reaction
After the electrolysis was over the anode solution was extracted with
ether, and the ethereal extract was fractionated in the manner previously
described.
With the greater portion distilled at 90°-120° and at about 130°
decomposition was observed to take place. The main fraction (9D°- I 20°)
when washed with water and dehydrated showed a specific gravity of
1.07 ( 15°), and was analysed to contain 29% of chlorine
It slowly decomposes into chloroaldehyde hydrate and chloroacetal when
boiled. From these properties the fraction appears to be monochloroaldehyde alcoholate




[Edited on 21-1-2025 by Hexabromobenzene]
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[*] posted on 21-1-2025 at 09:52


Quote: Originally posted by Hexabromobenzene  
We will also need excess current to oxidize the remaining ethanol.

What about using an oxidiser that is continuously regenerated by electrolysis? Permanganate or perhaps Ce4+. It would oxidise ethanol at least to acetaldehyde while chlorine is used only for the halogenation. Simultaneous but not competing reactions.




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[*] posted on 21-1-2025 at 12:34


Quote: Originally posted by bnull  
Quote: Originally posted by Hexabromobenzene  
We will also need excess current to oxidize the remaining ethanol.

What about using an oxidiser that is continuously regenerated by electrolysis? Permanganate or perhaps Ce4+. It would oxidise ethanol at least to acetaldehyde while chlorine is used only for the halogenation. Simultaneous but not competing reactions.


MnO2 doped anodes?




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[*] posted on 22-1-2025 at 01:46


At the first stage, this does not make sense. Ethanol is effectively oxidized by chlorine into acetaldehyde
And in the second stage after chlorination, this makes sense. You will not be able to use lead electrodes because of destruction. Carbon or lead dioxide
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[*] posted on 2-2-2025 at 19:58


Quote: Originally posted by Hexabromobenzene  
Recently an article on electrochemical chlorination of ethanol was found
At low temperatures the main product of chlorination is acetal chloroacetaldehyde. Only at 70 degrees dichloroacetaldehyde is formed
Also during pauses in electrolysis and diluted salt solution a lot of chloroacetic acid is obtained

In theory the process can be changed to obtain chloroacetic acid. We need to take so much salt that all the chlorine reacts with ethanol. We also need a acid(sulfuric, phoshporic to maintain Ph better in an acidic after sodium chloride gives up its chlorine and becomes hydroxide.
We will also need excess current to oxidize the remaining ethanol.
A very promising process. Chloroacetaldehyde can also be used to synthesize pyrazine
https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433...


I live in hope that people have done more work on such things in the slightly more than a century since this was published.

I hear the cool kids like Siegfried R. Waldvogel are doing their organic transformations in undivided cells and doing their best not to use exotic electrodes.
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