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Question?

Discussion in 'MCAT Discussions' started by xoomn, Jul 22, 2002.

  1. xoomn

    xoomn 10+ Year Member

    169
    0
    Feb 1, 2002
    Virginia
    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?
     
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  3. Diogenes

    Diogenes Succat 7+ Year Member

    2,829
    5
    Jan 30, 2002
    California
    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.
     
  4. missbonnie

    missbonnie floating 10+ Year Member

    778
    1
    Mar 21, 2002
    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
     

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