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Isolation of optical isomers
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mip:
I did a prac on resolution of tris(ethylenediamine)cobalt(III) ions. We had tris(ethylenediamine)cobalt(III) chloride trihydrate and reacted it in solution (at about 80 degrees C) with silver (+)-tartrate. We isolated crystals of the (+)Co(en)3.(+)tart.Cl (ie the (+)(+)diastereoisomer). We then dissolved these crystals in 5M HCl and added a solution of NaI. We then added a few mL of ethanol to complete the precipitation of the (+)tris(ethylenediamine)cobalt(III) iodide.
In my prac report I have to include reasons for adding HCl and NaI and I don't really understand why we used HCl, was it to change the pH of the solution, and if so, why?
Any help on this would be much appreciated. :)
mip:
Just incase anyone else was wondering, it turns out we dissolved the isomers in HCl as it is a conc. source of chloride ions and thus (somehow) increases the solubiltity of the crystal isomers... I hope that makes sense, Im exhausted!!!
movies:
Maybe you just need a high ionic strength in solution to help solubilize the complex.
Just guessing though, my inorganic techniques are lacking.
AWK:
This is a classic Werner synthesis from 1912.
The complex is good soluble in water but only sparingly in medium concentrated HCl solution.
Moreover, the complex is unstable in solution at RT, hence a precipitation should be fast
Werner, Ber. 45, 121 (1912)
Inorg. Synth. 2, 221-222, 223-225
Inorg. Synth. 6, 183-186
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