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Author: Subject: 1,2 dichloroethane synthesis
macckone
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[*] posted on 25-10-2021 at 10:12
1,2 dichloroethane synthesis


I am looking for a good OTC synthesis of 1,2 dichloroethane.

My first thought was to do a replacement reaction with zinc chloride and HCl similar to isopropyl and ethyl chloride using ethylene glycol.

The end product has an azeotrope with water even though it is not very soluble.

This looks like a good solvent. And has other uses such as Williamson ether synthesis.
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RustyShackleford
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[*] posted on 25-10-2021 at 10:28


as far as i know its not possible to create it from ethylene glycol, atleast by reasonable reagents. With HCl (even with CaCl2 or ZnCl2) it just makes 2-chloroethanol and doesnt substitute the other alcohol group. Youd have to make it from ethylene and chlorine gas. Ofc dibromoethane is possible to make by HBr and glycol, although the yield is bad, i got 48%.
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Myrcen
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[*] posted on 25-10-2021 at 11:03


Quote: Originally posted by RustyShackleford  
as far as i know its not possible to create it from ethylene glycol, atleast by reasonable reagents. With HCl (even with CaCl2 or ZnCl2) it just makes 2-chloroethanol and doesnt substitute the other alcohol group. Youd have to make it from ethylene and chlorine gas. Ofc dibromoethane is possible to make by HBr and glycol, although the yield is bad, i got 48%.


do you have tips for the reaction? i tried making it from glycol i bought at the hardware store. According to the msds it contained mostly ethylene glycol, 1-3% of boraxpentahydrate and a yellow fluorescent dye, maybe fluorescein. Even with 100 % excess of azeotropic HBr i never got more than 10 % yield.
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RustyShackleford
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[*] posted on 25-10-2021 at 11:20


I cant speak on the effect of impurities, since i used distilled glycol. But the way i did it was the following:
into a 500ml conical flask was added 154g NaBr (1.5 mol) + 135ml water.
250g H2SO4 95% (2.42 mol) was slowly drizzled in.
36.6g glycol (0.59 mol) added, contents refluxed under stirring for 6h.
mixture was cooled, poured into a separatory funnel, organic layer separated
extracted further with 20ml DCM (mostly to wash out the stuff that stuck to the sides of the sep funnel)
organic phase dried with CaCl2, then distilled
obtained 53g (48%) + 5g seemingly mostly pure that came below bp.


I think the sulfuric acid may be necessary to absorb the water thats released from substitution.
IMG_20210725_154856.jpg - 231kB
(had a trap with water to catch fumes, since it was letting off a moderate amount of HBr for the first couple hours)

[Edited on 25-10-2021 by RustyShackleford]
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Myrcen
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[*] posted on 25-10-2021 at 11:55


thank you! I think the impurities may be the reason for the low yield, although the hardware store stuff is reasonably pure. I will try it again with some purer glycol.
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macckone
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[*] posted on 25-10-2021 at 22:14


The procedure I am looking at is using ZnCl2, HCl, and ethylene glycol.
Then boiling off the product as it forms to push the reaction rather than refluxing or using a drying agent. The competing reactions form diglycol ether and dioxane. Using a dehydrating agent like sulfuric acid will push it toward dioxane.

I use a similar reaction for making isopropyl chloride. And it gives very good yield.
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Myrcen
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[*] posted on 26-10-2021 at 01:52


Quote: Originally posted by macckone  
The procedure I am looking at is using ZnCl2, HCl, and ethylene glycol.
Then boiling off the product as it forms to push the reaction rather than refluxing or using a drying agent. The competing reactions form diglycol ether and dioxane. Using a dehydrating agent like sulfuric acid will push it toward dioxane.

I use a similar reaction for making isopropyl chloride. And it gives very good yield.


I found a paper from 1881 where Schorlemmer mixed ethylene glycol with an excess of fuming HCl and heated it using a steam bath in a sealed tube. This procedure gave 1,2-dichloroethane. unfortunately the exact amouns of HCl and glycol are not given.
As Schorlemmer describes in the paper, there are other methods which are using PCl3 or PCl5 and ZnCl2 to chlorinate the glycol. Pyridine and Thionyl chloride also can be used to form 1,2-dichloroethane.

Attachment: schorlemmer1881.pdf (68kB)
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macckone
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[*] posted on 26-10-2021 at 13:18


Myrcen,
Thanks, that confirms it will work.
It also seems to confirm that ZnCl2 will work as a catalyst.
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RustyShackleford
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[*] posted on 27-10-2021 at 06:46


Quote: Originally posted by macckone  
Myrcen,
Thanks, that confirms it will work.
It also seems to confirm that ZnCl2 will work as a catalyst.

make sure to run it for a decent while, probably with a decent amount of ZnCl2 and H2SO4. because i recall seeing notes from someone that tried with just ZnCl2 and HCl, with no wortwhile yield.
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[*] posted on 1-11-2021 at 07:40


@RustyShackleford: That use of a large reservoir pipette as a gas trap is clever.

I haven't seen that before. Compact, simple, prevents suck-back, a handy rig.




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lithiumion656
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[*] posted on 28-5-2022 at 13:45


I have been investigating DCE as a high boiling alternative to the now essentially non-OTC DCM, to the extent that producing DCE through this method is more economical. Has this procedure actually been tried by anyone yet?
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