plante1999
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Potassium Isopropyl Xanthate (pictures)
Xanthates are a class of compounds formed when Carbon disulphide, an alcohol, and a base are reacted together. They consist of an alcoholoxide group,
a carbon disulphide moiety, are charged negatively and are connected to a metal ion. They are used extensively in ore flotation and cellulose
processing to cellophane and viscose. The potassium salts generally come as anhydrous non-hygroscopic solid, inverse of the sodium salts. In ore
flotation, finely ground ore are mixed with a solution of xanthate, in which air is bubled. A froth containing the purified ore form at the surface.
Sulphides ore are generally preferred, as much more efficient. The mechanism is based on a ligand formation around the metal atom that form a shell
off hydrophobic tail around the atom. The selectivity of the xanthate depends on the tail group, generally, smaller group are more selective.
I based my synthesis on the procedure resumed in organic syntheses which can be seen here:
http://www.orgsyn.org/demo.aspx?prep=CV9P0072
Since I lack ether, I modified the procedure to use strong excess of carbon disulphide to be sure the product would not be basic, as basic condition
degrades it.
Reagents:
Carbon disulphide J.T Baker A.C.S
Isopropanol, pharmacy 99% U.S.P
Potassium hydroxide, Flakes, Technical
50 ml of isopropanol was mesured and put into a 250 ml beaker. 4 g of potassium hydroxide was added. At first I mixed for 30 minutes before I realised
it would only dissolve if heated, so I heated to 40 C, dissolved all the hydroxide and cooled it to about 0 celcius. A small amount of saturated water
(about 2 ml) precipitated at that point, as well with some solid potassium hydroxide. Then, 5 ml of carbon disulphide was added with a lot of
stirring, and the temperature raised to 30 Celcius. The mixture was left to sit for 20 minutes. It was found to behave much like soap in the flask,
doing it's best to stay away from the water. Filtration in paper was quite hard because the product did not stick to the paper, as such a cloth was
used to press out the wash of isopropanol, totaling about 40 ml. The product was air dried at 5 C for one day (made the work space smell really bad).
The yield was 9g
Overall, the synthesis is fast and easy, the product has some aspects that makes it a special case in filtration. I planned to use it to purify a real
ore, but I got scammed, so it will have to wait.
The potassium hydroxide that does not want to dissolve in the cold isopropanol:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00246...
The colled solution of potassium hydroxide:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00247...
The reaction:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00253...
http://i1103.photobucket.com/albums/g469/plante1999/DSC00254...
Trying to filter with filter paper:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00255...
Product:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00256...
http://i1103.photobucket.com/albums/g469/plante1999/DSC00257...
I never asked for this.
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Mailinmypocket
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Nice! Are you going to also try making some complexes with it? I have a procedure for a nickel complex but it is done with the o-ethyl xanthate, might
be applicable to the isopropyl as well. I'm not sure though. The smell is horrible though, as you noticed 
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plante1999
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I could make complex yes, I don't have nickel salts on hand, and by experience nickel is really hard to dissolve in nitric acid. But I do have copper
sulphate, I will try and report.
I did not noticed due to chlorine exposure in the past, but father did..
I never asked for this.
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Metacelsus
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How interesting that another mad scientist is also working on this class of compounds! Here is my procedure:
4.36 g KOH (78 mmol) were partially dissolved in 25 ml iPrOH and 1 ml water was added
All the KOH dissolved. The mixture contained two layers: a lower aqueous one and an upper
alcoholic one. The mixture was chilled in an ice bath to 5 C and 4.84 ml CS2 were slowly
added with vigorous stirring. The cream-colored precipitate was collected by vacuum filtration on a
Buchner funnel, washed with ethyl acetate, and put in the dessicator overnight.
Yield: 12.12 g (90%)
On scaling up (up to 100x!) yields decrease to around 75%
Something to investigate: Sometimes, after the reaction, the aqueous layer is colored a deep red. This does not, however, happen all the time. Could
this be a polysulfide?
My interest in the compound is due to a further reaction I am studying (for a science fair project): its reaction with ethyl chloroformate to form
isopropyl xanthic anhydride.
[Edited on 29-12-2013 by Cheddite Cheese]
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Mailinmypocket
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Went through my binder and found the procedure for the prep of the ethyl version as well as the nickel complex. Apologies for not having a working
scanner at the moment but I wanted to share it with you in case it was of interest.
  
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DraconicAcid
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I seem to recall reading that the trithiocarbonate ion is orange-red. Perhaps this is what you're getting in the aqueous solution, CC? Long ago, I
tried reacting calcium hydroxide solution with carbon disulphide, to see if I would get 3 Ca(OH)2 + 3 CS2 -->
CaCO3(s) + 2 CaCS3(aq) + 3 H2O, driven by the insolubility of the carbonate. I did get an orange solution, but I
didn't try anything with the product.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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DraconicAcid
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Quote: Originally posted by Mailinmypocket  | | Went through my binder and found the procedure for the prep of the ethyl version as well as the nickel complex. Apologies for not having a working
scanner at the moment but I wanted to share it with you in case it was of interest. |
What's the adduct prepared in the next paragraph?
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Mailinmypocket
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So sorry for not having access to a scanner that makes reasonable duplicates. Anyways, this is the next paragraph. I'll find a reference for the full
paper if you need it:
Edit: the paper: synthesis and characterization of the adducts of bis(o-ethyldithiocarbonato)nickel(II) with substituted pyridines
By Renu Sachar and Sanjay Kapoor
Dept of chemistry, unjversity of Jammu, ambedkar road, jammu- 180 006(India)
Might give the full online result
[Edited on 29-12-2013 by Mailinmypocket]
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Metacelsus
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I tried direct reaction of CS2 and KOH (dissolved in water), but nothing happened. I think the presence of the alcohol, and thus formation
of the xanthate, is key to the formation of the red compound.
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Brain&Force
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Potassium isopropyl xanthate - so you have pix of PIX? 
Just be careful with disposal, xanthates appear to be toxic to aquatic life at concentrations of over 1 ppm. Apparently acids can cause the xanthate
salt to revert to the alcohol, CS2, and a salt formed by the acid and base.
You do some amazing work plante!
At the end of the day, simulating atoms doesn't beat working with the real things...
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plante1999
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I plan on making "synthetic" copper ore by passing hydrogen sulphide into a mixture of kielsegur and copper sulphate to mimic the gange of silica and
the sulphide ore. Although I would prefer cinnabar, it should be perfect to show the principle of flotation.
I did not poured the washes down the drain, not exactly for environmental reason, but more to use it ether in flotation or now, in complex making. It
contain all the reagents that was used in the synthesis plus lots of water.
I never asked for this.
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