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Posted by David Williams on February 19, 2006, 11:31 am
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-> High temperatures and pressures can "racemize" a mixture, making it
-> lose its net optical activity. The only way I can imagine the reverse
-> conversion occurring is if the environment is somehow asymmetrical in a
-> way that would favour the stability of one stereoisomer over the other.
-> Superimposed electrostatic and magnetic fields might do it, or
-> optically active crystals. However, I would expect this process to be
-> rare. If, as your quotations suggests, natural petroleum is "scalemic",
-> I would take this as evidence of a biological origin.
On further thought, I suppose it is possible for some sort of "symmetry
breaking" to occur, converting a racemic mixture to a scalemic one.
This might occur if molecules of the same stereoisomer can pack
together more closely than a mixture of molecules of opposite isomers.
Under high pressures, there would be a tendency for all the molecules
to be converted to just one isomer. I find it implausible that this
would be a significant effect in petroleum deposits, though.
It would be interesting to look at crude oil from different deposits
around the world. Do they all show the same distribution of
stereoisomers? A biological origin would predict that they should. A
non-biological one would probably produce different distributions in
different places.
dow
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