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Discussion in 'MCAT: Medical College Admissions Test' started by xoomn, Jul 22, 2002.

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  1. xoomn

    xoomn
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    This was a question in PR class compend.'s organic section:
    Amines that have 3 different groups are 'achiral' mixtures because of nitrogen inversion. I don't understand what they are saying here. Even though, nitrogen has 3 different groups still it's achiral?
     
    #1 xoomn, Jul 22, 2002
  2. Diogenes

    Diogenes Succat
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    The electron pair that is unbound can basically go from one side of the nucleus to the other. Do you recall what an sp3 orbital looks like? It is a big lobe on one side of the nucleus and a little lobe on the other side. Imagine that orbital as a balloon. If you squeeze on the fat end, the air goes into the small end and it gets bigger, while the big end gets small. And the other 3 groups move to accomodate the shift in the electrons' position. The result is a constant shifting between L and D. So basically there is no chirality there because the lone pair is not a constant 4th group -- it keeps changing sides.
     
    #2 Diogenes, Jul 22, 2002
  3. missbonnie

    missbonnie floating
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    It's achiral because the N is rapidly inverting -- it's never just at one configuration. Whereas a Carbon with 4 different groups attached is NOT inverting. It inverts rapidly because of its lone electron pair.

    Oh, looks like Diogenese already explain it thorougly.
    -bonnie
     
    #3 missbonnie, Jul 22, 2002
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