silly? phenol question

Tim Fitzwater TFITZWATER at somalogic.COM
Mon Aug 13 13:59:27 EST 2001

Oxidized phenol is pink to red.  The oxidation products are quinones, a wide
variety of phenolic coupling compounds and diacids.  Quinones are a,
b-unsaturated ketones that are capable of reacting with primary amines. 
Reaction of quinone with multiple amines forms stable crosslinked products. 
The diacids arise from further oxidation of orthoquinone, while phenolic
coupling products result from phenoxide radicals.  Quinones are faintly
yellow.  Phenolic coupling reaction compounds are intense yellow or red.
(1985 BRL Focus 7(2):12.)
The aqueous phase of water-saturated phenol is typically pH 3.0-4.5.  The
low pH is due to partitioning of the diacids into the aqueous phase. 
Partitioning will proceed more rapidly in a buffered solution of a higher
pH, however, phenol has a pKa = 10.0 and is much more susceptible to
oxidation at high pH.
0.1% 8-Hydroxyquinoline can be used as an additional preservative; this also
turns the phenol layer yellow, making separation of phases easier.


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