Sciencemadness Discussion Board - Preparation of dichloroethylene from ethanol?!

1.At what temperature can I dehydrate ethanol?

Ethanol cannot be dehydrated with heat. Water boils at a higher temperature than ethanol. A hygroscopic salt, typically potassium carbonate, is used to separate water from the alcohol. As for the reaction, I know very little organic.

bluamine - 1-12-2015 at 12:16

Quote: Originally posted by Detonationology

1.At what temperature can I dehydrate ethanol?

Hi dear!
I was not talking about drying ethanol, I know how to do that using sodium sulfate, copper sulfate, or even calcium oxide. I was talking about making ethylene as a first step of dichloroethylene synthesis process. I know heat doesn't do that, so I must use a catalyst (sulfuric acid) as it is mentioned above.

gdflp - 1-12-2015 at 12:25

Adding ethanol dropwise to sulfuric acid at or above 160°C, though I would increase that to about 175°C to ensure complete dehydration and minimize the formation of ether. This reaction will be a pain, hands down. Any reaction which involves two gases reacting with each other is enough trouble already, but that's using cylinders of compressed gas to have easy, precise control over the flow rate. Generating both the chlorine and the ethylene chemically will make it nearly impossible to control the flow rates precisely enough, and the reaction will thus be essentially undoable in an amateur lab.

If you want dichloroethane, I would use the reaction of Lucas' Reagent with ethylene glycol, which can be obtained by the permanganate oxidation of ethylene if absolutely necessary. Distilling antifreeze will be a much simpler endeavor however, if it is available.

Detonationology - 1-12-2015 at 12:30

Ah, (facepalm) I see now! As long as the catalyst stays hot, the dehydration should work without any heating of the ethanol. If the ethanol boils, you will risk not completely dehydrating the ethanol, and the lost ethanol vapor would likely H bond with the water upon contact.

bluamine - 1-12-2015 at 12:48

Adding ethanol dropwise to sulfuric acid at or above 160°C, though I would increase that to about 175°C to ensure complete dehydration and minimize the formation of ether. This reaction will be a pain, hands down. Any reaction which involves two gases reacting with each other is enough trouble already, but that's using cylinders of compressed gas to have easy, precise control over the flow rate. Generating both the chlorine and the ethylene chemically will make it nearly impossible to control the flow rates precisely enough, and the reaction will thus be essentially undoable in an amateur lab.

If you want dichloroethane, I would use the reaction of Lucas' Reagent with ethylene glycol, which can be obtained by the permanganate oxidation of ethylene if absolutely necessary. Distilling antifreeze will be a much simpler endeavor however, if it is available.

Well i was looking for ethylene glycol manufactur, because i was not sure about other chemicals existing in a antifreeze. How simple can distillation process be? Any specific conditions? & after it is done, must I use any other methods to separate any probably remaining impurities?

[Edited on 1-12-2015 by bluamine]

[Edited on 2-12-2015 by bluamine]

gdflp - 1-12-2015 at 12:55

Distillation of an ethylene glycol antifreeze is actually rather straightforward. A simple distillation suffices to separates the ethylene glycol from the various dyes and other crap in the antifreeze. Use a fractionating column if you wish to get purer ethylene glycol, but it isn't strictly necessary. A vacuum will also help to lower the necessary distillation temperature, but again it is not strictly necessary.

bluamine - 1-12-2015 at 12:55

I read first about another method based on reacting ethylene with hypochlorous acid to produce 2chloroethanol, then reacting this last with sodium hydroxide to get ethylene oxide, & lastly reacting ethylene oxide with water. It is clear that this process is very complicated, in addition, I read that it can cause some impurities in the final products.

bluamine - 1-12-2015 at 12:59

Dear gdflp
What about the other method I quoted from Wikipedia (ethanol chlorination)? (Only as an alternative process)

gdflp - 1-12-2015 at 13:09

I don't see how ethanol chlorination can lead to dichloroethane. Chlorination of ethane could proceed via a radical mechanism, but you again run into the issues of a reaction involving two gases. In addition, regioselectivity is going to be absolutely abysmal; the process is only viable on a massive industrial scale, where they have access to very efficient columns and the economy of scale.

Ethylene oxide is quite nasty, not trying to be condescending, but you don't sound equipped to handle it. And that method is very tedious for something as simple as ethylene glycol, it's simply not worth it.

What is your end goal here, dichloroethane or ethylene glycol? And if it is the former, do you specifically need that solvent, or can it replaced with another chlorinated solvent?

bluamine - 1-12-2015 at 13:30

I don't see how ethanol chlorination can lead to dichloroethane. Chlorination of ethane could proceed via a radical mechanism, but you again run into the issues of a reaction involving two gases. In addition, regioselectivity is going to be absolutely abysmal; the process is only viable on a massive industrial scale, where they have access to very efficient columns and the economy of scale.

Ethylene oxide is quite nasty, not trying to be condescending, but you don't sound equipped to handle it. And that method is very tedious for something as simple as ethylene glycol, it's simply not worth it.

What is your end goal here, dichloroethane or ethylene glycol? And if it is the former, do you specifically need that solvent, or can it replaced with another chlorinated solvent?

I do know some properties of ethylene oxide this us why I did not think I can do that process. I just mentioned it.
My final goal is ethylene glycol, no doubt that I can use other chlorinated solvents, otherwise, I would use chloroform instead, which is available for me, & I can even produce it if I needed some relatively big amounts, by reacting sodium hypochlorite & acetone.

NitreRat - 1-12-2015 at 13:41

By dichloroethylene do you mean 1,2-Dichloroethane (Ethylene dichloride) or 1,2-Dichloroethene (The alkene instead of the alkane)?

> 1. At what temperature can I dehydrate ethanol?
Ethanol can be dehydrated to Ethene (Ethylene) by heating it at above 150°C with concentrated sulfuric acid. I don't know the optimum quantity of H2SO4 catalyst but if you don't use enough H2SO4 you won't be able to get your reaction mixture to 150°C without the ethanol boiling off. I know this reaction can be easily done because I have often synthesized lots of Ethylene gas when attempting to synthesize diethyl ether but accidentally letting the reaction temp get too high. If you can't easily find any written procedures for this reaction online, just adapt an ether prep but run the reaction hotter. (This reaction is exceedingly dangerous, and could just spontaneous explode unless you are incredibly cautious and watch the reaction temps like a hawk)

> 2.Can sulfuric acid used as a catalyst turn to a gas during this process?
conc. H2SO4 boils at 338°C, so you shouldn't worry about it boiling off at the temps you should be working at. conc. Phosphoric acid is also a good dehydrating agent, with the added benefit of it being non-oxidising. Thus reducing potentially dangerous side reactions. If you can find any good preps for ethanol dehydration with H3PO4 I think that would be the way to go.

>3. In what conditions can I complete the second step using chlorine, ethylene, & iron (III) chloride?
Without opening Wikipedia to actually read up on it, I'd guess this is an industrial reaction. They probably have large reactors in china running at very high temps, very high pressures and a fancy catalyst supports. Reactions between two gasses is always tricky in a lab environment, never mind in the home lab. An alternative approach might be bubbling the generated ethylene gas through a solution of bromine in a solvent like n-hexane, or through a dilute aqueous solution of KMnO4 (look up Baeyer's reagent) to obtain 1,2-Dibromoethane (Ethylene dibromide) or Ethane-1,2-diol (Ethylene glycol) respectively. These compounds can then easily be converted 1,2-Dichloroethane (Ethylene dichloride).

>4. I found the paragraph below on wikipedia, it talks about an alternative method. Can anyone explain that?
They're probably referring to free-radical substitution reactions. This is another industrial reaction and it creates several different poly chlorinated by-products. This can be done in a home lab, but honestly its gonna' be much more trouble than it's worth.

If you have your heart set on making 1,2-Dichloroethene from Ethanol I would use the following steps:

1. Strongly heat a mixture of conc. Phosphoric acid and Ethanol in a flask with a gas take-off adapter.
2. Lead the gas into a flask containing an ice-cold alkaline solution of KMnO4 until no more purplish-pink color is observed.
3. Filter off the brown Manganese dioxide precipitate.
4. Fractionally distil the filtrate and isolate the ethylene glycol fraction
5. Reflux the ethylene glycol with an excess of Zinc chloride and conc. Hydrochloric acid
6. Distil out the lower boiling 1,2-Dichloroethane from the reaction mixture.
7. Dehydrohalogenate with an alcoholic solution of KOH to create Vinyl chloride gas.
10. Lead the gas into a flask containing bromine in a solvent such a n-Hexane until the solution turns colorless.
11. Isolate the 1,2-Dibromo-1-chloroethane and react with sodium chloride in DMF to convert it to 1,1,2-Trichloroethane.
12. Dehydrohalogenate with an alcoholic solution of KOH to create 1,2-Dichloroethene

bluamine - 1-12-2015 at 14:19

By dichloroethylene do you mean 1,2-Dichloroethane (Ethylene dichloride) or 1,2-Dichloroethene (The alkene instead of the alkane)?

> 1. At what temperature can I dehydrate ethanol?
Ethanol can be dehydrated to Ethene (Ethylene) by heating it at above 150°C with concentrated sulfuric acid. I don't know the optimum quantity of H2SO4 catalyst but if you don't use enough H2SO4 you won't be able to get your reaction mixture to 150°C without the ethanol boiling off. I know this reaction can be easily done because I have often synthesized lots of Ethylene gas when attempting to synthesize diethyl ether but accidentally letting the reaction temp get too high. If you can't easily find any written procedures for this reaction online, just adapt an ether prep but run the reaction hotter. (This reaction is exceedingly dangerous, and could just spontaneous explode unless you are incredibly cautious and watch the reaction temps like a hawk)

> 2.Can sulfuric acid used as a catalyst turn to a gas during this process?
conc. H2SO4 boils at 338°C, so you shouldn't worry about it boiling off at the temps you should be working at. conc. Phosphoric acid is also a good dehydrating agent, with the added benefit of it being non-oxidising. Thus reducing potentially dangerous side reactions. If you can find any good preps for ethanol dehydration with H3PO4 I think that would be the way to go.

>3. In what conditions can I complete the second step using chlorine, ethylene, & iron (III) chloride?
Without opening Wikipedia to actually read up on it, I'd guess this is an industrial reaction. They probably have large reactors in china running at very high temps, very high pressures and a fancy catalyst supports. Reactions between two gasses is always tricky in a lab environment, never mind in the home lab. An alternative approach might be bubbling the generated ethylene gas through a solution of bromine in a solvent like n-hexane, or through a dilute aqueous solution of KMnO4 (look up Baeyer's reagent) to obtain 1,2-Dibromoethane (Ethylene dibromide) or Ethane-1,2-diol (Ethylene glycol) respectively. These compounds can then easily be converted 1,2-Dichloroethane (Ethylene dichloride).

>4. I found the paragraph below on wikipedia, it talks about an alternative method. Can anyone explain that?
They're probably referring to free-radical substitution reactions. This is another industrial reaction and it creates several different poly chlorinated by-products. This can be done in a home lab, but honestly its gonna' be much more trouble than it's worth.

If you have your heart set on making 1,2-Dichloroethene from Ethanol I would use the following steps:

1. Strongly heat a mixture of conc. Phosphoric acid and Ethanol in a flask with a gas take-off adapter.
2. Lead the gas into a flask containing an ice-cold alkaline solution of KMnO4 until no more purplish-pink color is observed.
3. Filter off the brown Manganese dioxide precipitate.
4. Fractionally distil the filtrate and isolate the ethylene glycol fraction
5. Reflux the ethylene glycol with an excess of Zinc chloride and conc. Hydrochloric acid
6. Distil out the lower boiling 1,2-Dichloroethane from the reaction mixture.
7. Dehydrohalogenate with an alcoholic solution of KOH to create Vinyl chloride gas.
10. Lead the gas into a flask containing bromine in a solvent such a n-Hexane until the solution turns colorless.
11. Isolate the 1,2-Dibromo-1-chloroethane and react with sodium chloride in DMF to convert it to 1,1,2-Trichloroethane.
12. Dehydrohalogenate with an alcoholic solution of KOH to create 1,2-Dichloroethene

Well thank you for all thèse informations. Honestly it seems you are a genius. I wish thé best for you.
I am not sure about what must I use (alkane or alkine), I just read about this reaction on the link below:
http://www.ucc.ie/academic/chem/dolchem/html/comp/glycol.htm...
It is mentioned on that page that this reaction can be done in a lab, this is why I did prefered to use it. I have access to university's labs, so even if I couldn't do it at home, I would do it at university if the information mentioned there was correct.
I just made a small amount of hydrobromic acid, using seawater, it was really hard, & the harder is to reduce it to bromine though I don't need to

(my final purpose is to obtain pure ethylene glycol, as mentioned above)
I can buy phosphate easily & it is relatively cheap. So I can use it to make phosphoric acid. Permanganate solution can be bought easily, but it is really diluted (I don't have any idea about another commercial solution than the one existing in pharmacies), so i f I need some bigger amounts I can't buy from there (I am just supposing), I can look for an easy way to make it using a potassium salt, & manganese dioxide.

[Edited on 1-12-2015 by bluamine]

[Edited on 1-12-2015 by bluamine]

gdflp - 1-12-2015 at 16:19

Phosphoric acid is also a good dehydrating agent, with the added benefit of it being non-oxidising. Thus reducing potentially dangerous side reactions. If you can find any good preps for ethanol dehydration with H3PO4 I think that would be the way to go.

I wouldn't use phosphoric acid in a glass flask at 150°C+. The acid's etching effect on glass is not noticeable at room temperature, but it becomes pronounced at high temperatures. A glass flask full of phosphoric acid at those temperatures could be completely destroyed, and 160°C phosphoric acid is not something which I would want spilling over a hot plate.

7. Dehydrohalogenate with an alcoholic solution of KOH to create Vinyl chloride gas.
12. Dehydrohalogenate with an alcoholic solution of KOH to create 1,2-Dichloroethene

Dehydrohalogenations are not very easy to do that precisely. There would be significant losses due to side reactions if you tried to get a haloalkene from a dihaloalkane.

gdflp - 1-12-2015 at 16:27

It is mentioned on that page that this reaction can be done in a lab, this is why I did prefered to use it. I have access to university's labs, so even if I couldn't do it at home, I would do it at university if the information mentioned there was correct.
I just made a small amount of hydrobromic acid, using seawater, it was really hard, & the harder is to reduce it to bromine though I don't need to

If you're goal is to get ethylene glycol, then the oxidation of ethylene with potassium permanganate is the best, and most direct, option. I would boil down the dilute permanganate solution to concentrate it as much as possible, then simply bubble ethylene through it. From there, neutralize excess permanganate in the solution with very small amounts of sodium metabisulfite or another similar reducing agent, be careful not to add too much and redissolve some of the manganese dioxide as manganous ions. Finally, filter off the manganese dioxide sludge, and fractionally distill the mother liquor to get relatively pure ethylene glycol. Be aware that you won't get very much with this process, theoretical yield is ~30ml ethylene glycol per liter of concentrated aqueous potassium permanganate.

bluamine - 2-12-2015 at 00:50

I will use some alumina ceramic instead, does is resist phosphoric acid?

NitreRat - 2-12-2015 at 01:16

7. Dehydrohalogenate with an alcoholic solution of KOH to create Vinyl chloride gas.
12. Dehydrohalogenate with an alcoholic solution of KOH to create 1,2-Dichloroethene

Dehydrohalogenations are not very easy to do that precisely. There would be significant losses due to side reactions if you tried to get a haloalkene from a dihaloalkane.

Yes, I was aware that these steps were a bit assumptious. If nothing else, I was just trying to highlight how frustrating and low yielding the processes of ethanol to dichloroethene would be. In a real lab I would probably use Potassium tert-butoxide in an ether solvent and control the stoichiometry as best I could for the dehydrohalogenations, but in a real lab I would probably chose to start with acetylene instead of ethanol.

CaC2_(s) + 2 H2O_(l) → C2H2_(g) + Ca(OH)2_(s)
C2H2_(g) + Br2_(hexane) → C2H2Br2_(l) + (over-brominated product by-product, but tetrabromoethane might also be useful for something so I wouldn't throw it away)
C2H2Br2_(DMF) + 2NaCl_(DMF) → C2H2Cl2_(l) + 2NaBr_(DMF)

[Edited on 12/2/2015 by NitreRat]

NitreRat - 2-12-2015 at 01:32

Thanks, for the info. I completely forgot about it's corrosive effect on glassware. Molten hydroxides, Hydrofluoric acid and hot Phosphoric acid are the major glass killers, if my memory serve me well. I've even seen hot solutions of NaOH in glycerol eat through borosilicate. The reason I initially suggested H3PO4 is because I believe that's how the reaction is done industrially (or at least hydration of ethylene to ethanol). Hot activated alumina, Phosphorus pentoxide(if you're brave enough) and Benzenesulfonic acid(?) might be potential alternatives. H2SO4 is still probably the best bet at this scale though. There must be a tonne of available literature out there for the initial dehydration reaction.

[Edited on 12/2/2015 by NitreRat]

NitreRat - 2-12-2015 at 02:41

I will use some alumina ceramic instead, does is resist phosphoric acid?

Only if your alumina ceramic round bottom flask is compatible with your other ground glass joints.

I suppose you could get away with doing that reaction in a tin can, with a copper condenser welded on the top, like some of the guys did when making decarboxylating sodium benzoate to benzene. Nile Red's video on it even looked quite professional.

bluamine - 2-12-2015 at 03:02

Only if your alumina ceramic round bottom flask is compatible with your other ground glass joints.

This is noticeable bro lol

but tin melting point is too low.. If I overheat it melts..

bluamine - 2-12-2015 at 09:40

What is exactly the temperature condition? How much sulfuric acid & ethanol should I use to obtain this amount (30 ml) of ethylene glycol?

MrHomeScientist - 2-12-2015 at 10:21

Tin cans aren't actually tin, they're usually steel.

NitreRat - 2-12-2015 at 11:19

I drew a diagram of the sort of set-up you might employ for this reaction. Unfortunately, unless I miscalculated, the stoichiometry doesn't work out very nicely and 30ml of ethylene glycol corresponds to about 34g of KMnO₄ and a similar amount of H₂SO₄. Which would be a very concentrated solution in 250ml of water. So you would probably get a lot of over oxidation. However in my equation I assumed that the MnO4^- was being reduced all the way down to Mn2⁺. The nice thing about this way of performing the reaction is that you get a nice color change, from dark purple to almost colorless pale pink in the drechsel bottle. Which indicates when the reaction is complete.

bluamine - 2-12-2015 at 11:35