2,9-bishydroxy-1,10-phenanthroline colour?
Uncle Al Schwartz
Charles Stuart wrote:
>
> I have been making 2,9-bishydroxy-1,10-phenanthroline and each batch I
> make seems to be a different colour! The reference sample I was given
> is white crystals and the samples I have made have been from dried
> blood red through orange to pastel yellow in colour. Analysis of the
> samples show them to be pure. How can this be? The only explanation
> I can think of is many different states of hydration. A brick red
> sample was the monohydrate. When I dissolved a small quantity in
> water and then evaporated the water off, what I got back was mid
> yellow in colour.
>
> Can anyone explain this multicoloured chemical?
>
> Charles E. T. Stuart
> cha...@luna.co.uk
> HAIRY HUMAN HOMEPAGE: http://www.luna.co.uk/~charles/
> Genetic research into human body hair
[Hairy human? Don't overlook phloretin (not phloridzin - it also
kills kidneys) and mimosine. Topical application of either (the
later after plucking) will get you your hairless ape. In any
case, the Somatic Fur Queen of SFU has already identified the
(a?) genetic basis of hair growth. She's got mice which look
like explosions in a mattress factory.]
Back to our program... I bet the colored stuff has an EPR
signal. Try stirring the colored stuff over a little zinc dust
in acid or base, sulfite, dithionite, or aqueous borohydride
(cyanoborohydride is better). It sounds like you are getting a
smidge of oxidation to semi-quinone, quinone, and quinhydrone.
Also check for trace amounts of transition metals.
--
Alan "Uncle Al" Schwartz
Uncl...@ix.netcom.com ("zero" before @; 24 hour delay)
http://www.netprophet.co.nz/uncleal/
(Toxic URL! Hazardous to children, Democrats, and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Charles Stuart
Eric Lucas
Charles Stuart wrote:
>
> I have been making 2,9-bishydroxy-1,10-phenanthroline and each batch I
> make seems to be a different colour! The reference sample I was given
> is white crystals and the samples I have made have been from dried
> blood red through orange to pastel yellow in colour. Analysis of the
> samples show them to be pure. How can this be? The only explanation
> I can think of is many different states of hydration. A brick red
> sample was the monohydrate. When I dissolved a small quantity in
> water and then evaporated the water off, what I got back was mid
> yellow in colour.
>
> Can anyone explain this multicoloured chemical?
I wouldn't sweat it at all. Electon-rich and polycyclic aromatic
compounds (i.e. easily oxidizable materials) often are contaminated by
very small amounts of highly-colored impurities. Quninones and such.
If you're really concerned about the color, recrystallize from a good
solvent like methylene chloride, and use a small amount of decolorizing
carbon (activated charcoal.) A mentor of mine in college once gave me
the wisdom that, if I could get a compound to crystallize from a superb
solvent like methylene chloride, it would come out exquisitely pure,
because all impurities would be soluble.
However, if color doesn't matter to you, chances are it really is
analytically pure (as your anayses show) and can be used in subsequent
reactions without further purification. Water could react with one of
these minute impurities to quench a dark color. I doubt if hydration
really modifies the spectrum of the pure compound, especially since you
were given a colorless sample of this compound.
Good luck,
Eric