Re: Acetone + ccHCl yields chlorine?

On Oct 8, 3:01 pm, WS <novalidaddr...@xxxxxxxxxxxxxx> wrote:
Dear Experts,

I have prepared acidic acetone by mixing 95% (v) acetone and 5% (v)
conc. HCl in order to precipitate proteins from serum. After a few
minutes. the solution turned yellowish green (typical chlorine color),
what I didn't expect. There seems to be a weak smell of chlorine as
well. When I add up to 500ul (I haven't tried more) to 50ul serum,
then the green color vanishes quickly.

Can anyone explain what has happened there? acetone is 99.8% pure and
pharmaceutical quality and HCl is p.a (means appox. ACS grade). I
don't think acetone itself cold oxidize Cl- to elementary chlorine.
Could some impurities be the cause?

Thanks for your suggestions!

Wo

What you are observing is the pinacol coupling reaction of acetone.
Most reactions are reversible equilibrium reactions. In your case HCl
adds (reversibly) across the acetone ketone double bond to give what
might be called a chlorohydrin, or specifically, 2-chloro-2-hydroxy-
propane. You are working in the presence of light. Bad idea. To avoid
the formation of trace chlorine, you need to work in total darkness.
Light induces free radical reactions that give the pinacol coupling
reaction. So yes, in your case acetone is oxidizing HCl (in a
reversible equilibrium sense) to give Cl2 and two molecules of acetone
are reduced and coupled to give pinacol. Since this is reversible, the
opposite reaction occurs when excess HCl is removed by reaction with
serum proteins.

.

Relevant Pages

  • Re: copper etching
    ... >> zero becuase of the instant reaction, ... The smell of Cl2 is quite different from the smell of HCl. ... peroxide; it did not mention the reaction of HCl with H2O2 ... instead it was written that elemental chlorine is reduced to ...
    (sci.chem)
  • Help with reaction orders and rates please!
    ... others) and recorded the reaction times. ... also the initial concentrations of the HCl, acetone and iodine. ...
    (sci.chem)
  • Acetone + ccHCl yields chlorine?
    ... HCl in order to precipitate proteins from serum. ... There seems to be a weak smell of chlorine as ... don't think acetone itself cold oxidize Cl- to elementary chlorine. ...
    (sci.chem)
  • Re: copper etching
    ... when the liquid is heated somewhat. ... it did not mention the reaction of HCl with H2O2 ... instead it was written that elemental chlorine is reduced to ...
    (sci.chem)
  • Re: copper etching
    ... This would be most likely a direct oxidation reaction of Fe ... hydrogen from displacement by HCl and oxygen by ... > evoled when iron nails are reacted with concentrated HCl. ... I know the unpleasant smell from nails and many other metal items. ...
    (sci.chem)