Sciencemadness Discussion Board

hydrogen fluoride out of 1,1-difluoroethane

ninhydric1 - 31-7-2017 at 17:58

I was browsing my local superstore the other day and came upon a computer duster that claimed to have >99% difluoroethane. I also read up somewhere in a SM thread that the combustion of difluoroethane yields hydrogen fluoride. So out of curiosity, is it possible collect nearly pure hydrogen fluoride (as hydrofluoric acid) through the combustion of the difluoroethane? Obviously, I'm not going to try this in my home lab, but what would the setup be?

[Edited on 8-1-2017 by ninhydric1]

Assured Fish - 1-8-2017 at 02:07

The fluoride carbon bond is generally regarded as the strongest bond in all of chemistry, combined with the fact that fluorine is a stronger oxidizer than oxygen itself, combustion or burning is just oxidation and thus you could not break the carbon fluoride bond by burning difluoroethane or any other fluoride carbon bond.

I could be wrong but its unlikely, Could you quote where it stated that combustion of difluoroethane yields HF.

ninhydric1 - 1-8-2017 at 09:08

@Assured Fish


It has to be determined on a case-by-case basis, but I absolutely would not use difluoroethane at all for this, as it is flammable and its combustion yields some very deadly compounds such as HF and fluorophosgene. If you should accidentally ignite it, that could be a disaster.
--zts16

http://www.sciencemadness.org/talk/viewthread.php?tid=71284#...

unionised - 1-8-2017 at 11:46

High temperature reaction with steam should produce HF.
It's also less likely to produce carbonyl fluoride..

It's not obvious what you would make the reaction vessel from.

ninhydric1 - 1-8-2017 at 11:53

Possibly PFA (perfluoroalkoxyalkanes). They do sell flasks made of PFA, and it seems to be one of the most resistant plastics.

clearly_not_atara - 1-8-2017 at 12:22

Fluorite (the rock) is preferable since it can be decomposed at room temperature with sulfuric acid and distilled to yield hydrofluoric acid with nearly no contaminants. Furthermore it is available as an ornamental stone practically everywhere in unlimited quantities. If this is still too expensive you might be able to find a mine within driving distance and get a large quantity for free.

If any part of this process sounds too difficult you simply have no business making HF. It's dangerous and everything you can make with it is also dangerous.

Assured Fish - 1-8-2017 at 15:47

Fascinating, never have i felt so intrigued being proven wrong.

unionised - 2-8-2017 at 12:23

Quote: Originally posted by ninhydric1  
Possibly PFA (perfluoroalkoxyalkanes). They do sell flasks made of PFA, and it seems to be one of the most resistant plastics.

I said "high temperature", and I meant it.
I'm thinking "red hot" or something like that, to get enough energy to break the C-F bonds.
Anything with C-F bonds is (necessarily) going to fail.
When I saw the start of Clearly_not_Atara's post
"Fluorite (the rock) is preferable since it ..."
I wondered at first if they were suggesting a furnace tube made from fluorite.
I think it might do the job, but I don't think it's very practical.

ave369 - 3-8-2017 at 06:13

Another one wants to make HF. Why can't you just use Whink? Whink is the only form of HF that is even remotely practical in an amateur setting.

Texium - 3-8-2017 at 09:29

Quote: Originally posted by ninhydric1  
@Assured Fish


It has to be determined on a case-by-case basis, but I absolutely would not use difluoroethane at all for this, as it is flammable and its combustion yields some very deadly compounds such as HF and fluorophosgene. If you should accidentally ignite it, that could be a disaster.
--zts16

http://www.sciencemadness.org/talk/viewthread.php?tid=71284#...
Ha, I don't think quoting my post that is strongly cautioning someone against igniting difluoroethane really helps your case.

ninhydric1 - 3-8-2017 at 09:56

Note that this post was meant to think theoretically, and not to actually do it. Please read my original post, as it says that I wasn't going to actually try it. Please read an OP carefully instead of jumping straight to conclusions.

ave369 - 3-8-2017 at 13:57

It is common practice for kewls to ensure everyone that no, they are totally absolutely not making HF, phosgene or something, they are just inquiring (in reality, they totally intend to try). If they tell everyone that they do intend to try, no one here will help them, so they lie. So it's a warning just in case.



[Edited on 3-8-2017 by ave369]

BromicAcid - 3-8-2017 at 15:39

Look into using a spark gap or constant electric discharge or an arc. Those used to be favorites of chemists instead of just a naked flame.

ninhydric1 - 3-8-2017 at 20:19

@ave239

Ok. Let me get this straight. Even before I made this post, I knew that you could get HF from the store as Whink rust remover. If I were one of those kewls, I wouldn't have bothered making this post. Then why did I? I had an idea, and I was curious if it would work, so I decided to run it through the seasoned members of this forum. And I have never been affiliated, nor do I have the desire to be affiliated with, any synthesis or acquisition of any chemicals that are related to drugs or chemical weapons. So please have substantial evidence before you jump from assumptions to conclusions.

@BromicAcid Thank you for the info. Through lurking on this forum, I have learned that gases such as ozone can be produced through such methods (a video by TKOR about Jacob's ladder reminded me of it :)). I will look into the preparation of hydrogen halides via spark gaps, etc.

[Edited on 8-4-2017 by ninhydric1]

XeonTheMGPony - 3-8-2017 at 20:22

Look up silent arc discharge. as you can make a sealed chamber for reactions.

CrossxD - 5-8-2017 at 00:39

react it with sodium hydroxide and than with conc. sulphuric acid.... i think :D

Rhodanide - 25-8-2017 at 13:24

I've found that Glass etchant works great for most of the purposes where HF is required. (Mine is Ammonium Bifluoride and HF in H2O.) [It's probably got other crap in there, but I digress]
You could probably get HF or AMBF from etchant cream, too.

chornedsnorkack - 26-8-2017 at 22:58

Quote: Originally posted by Assured Fish  
The fluoride carbon bond is generally regarded as the strongest bond in all of chemistry, combined with the fact that fluorine is a stronger oxidizer than oxygen itself, combustion or burning is just oxidation and thus you could not break the carbon fluoride bond by burning difluoroethane or any other fluoride carbon bond.

I could be wrong but its unlikely, Could you quote where it stated that combustion of difluoroethane yields HF.


C-F bond is stronger than C-O, but H-F is also stronger than H-O bond. The reaction
COF2+H2O->CO2+2HF
goes to right, spontaneously and violently.
So even if the initial reaction were
2C2H4F2+5O2->2CO2+4H2O+2COF2
the end result would still be
2C2H4F2+5O2->4CO2+2H2O+4HF

Now as for materials of reaction vessels, standard materials to handle F2and HF are metals which passivate well - Cu and Ni. Which are heat resistant and common. Because of softness and good heat conductivity of Cu, Cu tubes and tools of working them are common.
If you want to burn fluorocarbon compounds and prevent escape of any noxious fumes, you´d want to ensure that combustion goes to completion, to CO2 and HF, and then condense/scrub out the HF vapours. How would you set up a condenser to safely capture HF vapours and recover them as (dilute) hydrofluoric acid?