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sp2 or sp3

Discussion in 'MCAT: Medical College Admissions Test' started by sdnstud, Apr 6, 2004.

  1. sdnstud

    sdnstud 1K Member
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    quick question. a nitrogen (N) attached to 2 carbons and have 2 lone pairs is sp3. But my instructor says if the same nitrogen is part of an aromatic ring, it is sp2. is this true?
     
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  2. Idiopathic

    Idiopathic Newly Minted
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    Arent all atoms on an aromatic ring sp2?
     
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  3. TripleDegree

    TripleDegree Joker Doctor
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    Unless perhaps there was a double bond involved somewhere?

    What form would N appear on an aromatic ring? As an NH2 group?
     
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  4. CanIMakeIt

    CanIMakeIt Fellow
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    only if there is a possibility of donating the lone pair for the stability of aromatic ring then those electrons become delocalized and N is considered sp2 otherwise it will still be sp3

    good example is coffee structure:

    http://www.brynmawr.edu/news/ask/index.shtml

    In the ring on the left.....at first glance you will think that N is sp3 hybrid but N gives its electrons to the ring and O becomes negative charge..... when both N do that, the ring is stabilized and electrons fron N lone pairs are delocalized making it sp2

    I hope it was helpful
     
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  5. krull

    krull Membership Revoked
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    If the resonance structure of the the molecule is more stable when Nitrogen has a double bond such as R2N=R then nitrogen is Sp2 hybridized. If the resonance structure of the double bonded Nitrogen atom is a less stable product than its single bonded resonance form, then the molecule is Sp3 (R-N-R)
     
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  6. jhk43

    jhk43 Senior Member
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    coffee is aromatic rite?

    4(1) + 2 = 6?
     
  7. Nuel

    10+ Year Member

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    Actually on the picture there are 10 aromatic pi electrons. I don't think aromaticity is tested this MCAT season.
     
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  8. liverotcod

    liverotcod Lieutenant Crunch
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    In pyridine, for example, the Kekule structure is drawn with one single bond and one double bond--a fiction, obviously, but it does suggest the correct answer of sp2. In pyrrole, which is a little weird, you get (technically) sp3 hybridization but the extra stability of the aromaticity forces the non-bonded pi electrons to delocalize and take on sp2 character.

    See this word doc about aromatics (page 20)
     
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  9. babinski bob

    babinski bob Senior Member
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    By definition, one of the criteria of aromaticity is planarity. Therefore all atoms part of an aromatic system are sp2 hybridized.
     

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