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View Diary: BP Catastrophe Liveblog Mothership: 44 - organic chemistry 101 Edition (105 comments)

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  •  The resonant nature of benzene and other (3+ / 0-)
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    RunawayRose, cotterperson, NNadir

    aromatics does involve sharing the electrons all the way around the ring and the links I gave go into more detail about that. I don't think I've ever seen cyclohexatriene but you're right that benzene does not have fixed double bonds.

    We definitely underestimate many of the risks of our current energy sources; we are dulled by familiarity.

    •  Well, cyclohexatriene exists only in the minds of (1+ / 0-)
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      Wee Mama

      computational chemists and of course ring currents are measurable via NMR and other physical systems.

      When I was a kid I used to be fascinated by the strength of ring currents in "partially aromatic" systems like 2nd period heterocycles like furans and pyrroles.

      Then I grew up.  

      It is of course mechanistically useful to consider aromatic like intermediates in cycloadditions, sigmatropic rearrangements etc and so on, and for that matter, anti-aromatic systems like cyclobutadiene, a known, but extremely unstable compound.  

      An interesting fun case that is mildly related is Winstein's bridged carbocation, effectively an aromatic system if one thinks about it, most famously represented by the norborenyl cation that caused so much kvetching by H.C. Brown who was sort of a poster child for the notion that one can win the Nobel Prize and still be completely and obviously wrong.

      Again NMR experiments showed - not that Brown seemed to get it - that the time scale for any "equilibration" between localized ions - was so short, that the energy state of the molecule was completely indeterminant because of the uncertainty principle.

      I think that Brown's actual point may have been, "I am H.C. Brown and therefore I am God."   Actually the norborenyl cation involved God only inasmuch as it may have been God's means - and I'm speaking as an atheist here - of showing that 1) she has a sense of humor, and 2) that winning the Nobel Prize can be bad for you.

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