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Posted by David Williams on February 17, 2006, 9:35 pm
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-> I found a paper by Thomas Gold (not an unbiased source !) which says
-> that optical activity is one of four pointers to petroleum being of
-> biogenic origin (one of the others is the preference for molecules with
-> an odd number of carbon atoms, which he interprets as implying breakdown
-> of a larger molecule of biological origin).
-> The page was at <http://www.people.cornell.edu/pages/tg21/usgs.html> but
-> it returns "not found" and you will have to use Google's cache.
-> He doesn't say in which direction the optical activity occurs, and
-> according to _this_ paper
-> <http://www.iop.org/EJ/article/1742-6596/6/1/014/jpconf5_6_014.pdf> very
-> high pressures can convert a racemic mixture to a scalemic one (that
-> word was new to me !)
I'm familiar with the word "racemic", but not "scalemic". Maybe it's a
lot younger than I am.
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.
dow
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