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Has anyone heard of P and M notation?

  1. Nov 22, 2005 #1

    chem_tr

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    Has anyone heard of P and M notation???

    Hello,

    A friend of mine has asked a question about a molecule, we think the molecule was a biphenyl molecule with two nitro groups on each benzo unit, along with two carboxylic acid moieties on each ring. So the molecule was shown to be in two isomers as P and M. Do you have any knowledge about P and M type isomers?

    PS: We know that two phenyl units are placed perpendicular to each other.
     
  2. jcsd
  3. Nov 22, 2005 #2

    movies

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    These molecules have an axis of chirality, that is, they are chiral without having any asymmetric carbon atoms. The P and M are like S and R in assigning the handedness of a chiral carbon center.

    To assign one the handedness, look down the chiral axis so that the two pairs of substituents are perpendicular to one another. Assign each group a priority number, just as you would with a chirality center, but assign all of the groups in front before any of the ones in the back. Once you get used to it, you can assign the handedness now, but I often find it easier to treat the structure like it was a center of chirality. To do this, do just like you would otherwise and place the lowest priority group in the back of the structure and rotate from priority 1 to 2 to 3. Make sure you keep the priority assignments correct! M and P correspond to clockwise and anti-clockwise ordering of the groups, respectively (just like R and S).
     

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  4. Nov 23, 2005 #3
    Is this part of the Kahn-Ingold-Prelog system?
     
  5. Nov 23, 2005 #4

    chem_tr

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    Thank you very much. I constantly learn a great deal of knowledge from you. It is very good thing to have you here.

    To tritertbutoxy: As I understood from Movies' message, it works similar to CIP system; but with one exception: This system is used in chiral molecules with no asymmetric atom. This is possible in biphenyl, binaphthyl, etc. As to the designations, I am still inexperienced, so let's just read Movies' message.
     
    Last edited: Nov 23, 2005
  6. Nov 23, 2005 #5

    movies

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    Yes, this is covered by the C-I-P system. See this paper and the references theirin: Angew. Chem., Int. Ed. Engl. 1982, 21, 567-583.

    Chem_tr: It's my pleasure to help you, and others, out. The questions here cause me to learn new things!
     
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