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papaya
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Few more questions regarding dichloroethane uses - how easy it will be to generate acetylene (with NaOH) and also can one obtain ethylene glycol by
hydrolysis of it with NaHCO3 ? In both cases - will solids react with it or is it possible only in water solutions ? Especially glycol is interesting,
because if dry NaHCO3 will react then one can prepare completely water free glycol this way.
Also what else it can be used for?
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bbartlog
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2NaHCO<sub>3</sub> -> Na<sub>2</sub>CO<sub>3</sub> + H<sub>2</sub>O + CO<sub>2</sub>
You want anhydrous, don't use sodium bicarbonate. I don't think it's basic enough anyway. Ca(OH)<sub>2</sub> wouldn't be a bad choice I
think.
The less you bet, the more you lose when you win.
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papaya
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I meant
(CH2CL)2 + 2NaHCO3 --> (CH2OH)2 + 2NaCL + 2CO2
but all these I believe need high temp/pressures and won't work on a lab scale.
Btw, I did my first thiokol synthesis experiment today, first boiled 20g NaOH with12g S in about 100 ml of water, even after half an hour not the
whole sulfur was dissolved and there started to appear strong H2S smell so I finished boiling and filtered it to obtain clear dark red solution (I
have some serious spills during that, so yields are bad). While still warm I gradually added dichloroethane 15ml of total. Since it was about 50 °C
and nothing appeared to take place I put it on a plate to heat a little bit.
As I read in the paper posted here
"Classic Chemical Demonstrations
THE ROYAL
SOCIETY OF
CHEMISTRY
95. Making polysulphide rubber
"
which says to not heat above 83°C otherwise it'll start to boil I was feeling comfortable, however at about 71°C solution boiled instantly and
some solution spatter out of the flask. Later I found that there's an azeotrope with water with b.p about 70 C (from wiki). Also in that paper ratios
look very weird (8g sulfur to 5 g NaOH and 20 ml(!) of dichloroethane) so I found hard way that the information presented there is at least
questionable. Also if I remember correctly woelen mentioned that the reaction is slightly exothermic, well in my case (ratios) it was stronger and
when taken from the heater the temperature didn't fall below 70C for a long time while some yellow lumps started to appear and grow so once started I
could take it off and watch what happens. however that way too much dichloroethane boiled away and I thing some kind of reflux is necessary for better
results.
Now what I need is a good procedure for the highest yields(ratios I took I somehow calculated myself which maybe not ideal), as I think that rubber
itself is interesting and deserves further experimentation (also for pyro guys here - it must be an ideal fuel, as there's sulfur and carbon ''blend''
on molecular level, just add some K nitrate and get "B.P. polymer version", lift up rockets, etc., only obstacle I see is the lack of some solvent for
it which I hope exist).
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papaya
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Btw. I didn't throw away the liquid remained after synthesis and separation of rubber that was really stinky and from curiosity I decided to see what
happens if I add some TCCA to it. A vigorous but controllable reaction started with heating and nearly transparent solution turned into ''milk''
quickly. I was pondering what happened to it and as far as I can guess that must bree free sulfur generated by oxidation of remaining polysulfanes and
maybe also thiosulfate in the solution. I didn't separate it yet but I'm nearly sure it's sulfur, so if true there's a good way to recover sulfur from
spent solution (I believe it will work also with common bleach instead of TCCA), what do you think?
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bfesser
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Thread Split
21-7-2013 at 13:46 |
woelen
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TCCA itself also may lead to formation of solid material. It produces cyanuric acid and this is only sparingly soluble in water. At high pH, however,
this is more soluble, giving cyanurates.
What is the color of the precipitate? Is it white like milk, or yellow. If it is really white, then I have severe doubts that it is sulphur.
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papaya
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Yes I'm aware of cyanuric acid, now when I look into container there's a yellow-white precipitation which is I think a sulfur. Another interesting
thing here that the solution now smells acidic (unlike previous worse-than-rotten-egg smell, which is also the smell of polymer, what is it?) much
more like HCL and when I dropped a bit onto concrete floor it started to fizzle like acids do giving off CO2, very weird given that the solution is
prepared from lye!
[Edited on 22-7-2013 by papaya]
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woelen
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If you use TCCA, then formation of acid is not strange at all. Much of the chlorine in the TCCA may end up as HCl in a redox reaction. I once
witnessed this myself, when I added TCCA to ammonia. After the reaction the solution was strongly acidic!
[Edited on 23-7-13 by woelen]
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papaya
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Then one must think in chlorine generator setup like yours one doesn't need to use HCl since it can form from the reaction.. Is it possible that
sulfuric acid formed from oxidation of sulfur with TCCA ? 
Anyway in this case it's even better, as acidic solution will also convert thiosulfate into sulfur after polysulfides. But TCCA is not economical,
hopefully bleach also works, and to be sure if really sulfur forms a cleaner test is needed like dissolving S into NaOH and then add bleach to check
what happens.
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Hexavalent
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Not to advertise, but currently on eBay there is 2 kg of Alfa Aesar 1,2-dibromoethane...
http://www.ebay.co.uk/itm/1-2-Dibromoethane-2kg-/32116623508...
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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plante1999
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In my book, preparative method of polymer chemistry, I found two procedure that are not lab demonstration, but practical synthesis. the first one is
to make particles of polymer suitable for analysis (It use a polysulphide sol. made with sulphur and sodium sulphide), but the second preparation is
used to make dust of the polymer coated with magnesium hydroxide, the interest? When put into shape, HCl is added and a plain piece of the rubber is
made.
When I will have more time i will transcribe the text here.
I never asked for this.
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