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"reactions at the 2 position"-- what does the MCAT mean by this??

Discussion in 'MCAT Study Question Q&A' started by mytoechondriac, Jun 18, 2008.

  1. mytoechondriac

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    I'm looking at the topics list, and it has this under the Orgo section: "reactions at the 2 position: halogenation and substitution". I don't know what they mean by the 2 position... I've looked online and in 2 orgo texts, and I'm still clueless. Can anyone tell me what this is??
     
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  3. RySerr21

    RySerr21 i aint kinda hot Im sauna
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    the two position is the 2nd carbon once you name the molecule..i believe.
     
  4. nfg05

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    This is correct, and in this context it's helpful to know that "reactions at the 2 position" is listed under the heading "Carboxylic acids" meaning what they are referring to as the 2 position is what most people would call the alpha carbon of the carbonyl. Specifically, the tendency of carboxylic acids (and other carbonyls) to lose their acidic alpha-hydrogens, thereby forming a carbocation and subjecting the alpha carbon to nucleophilic attack, whether by a halogen or some other nucleophilic subsitution.

    Ex. CH3CH2CH2COOH. The red C is the alpha carbon, or 2nd carbon when the molecule is properly named. Blue is beta, green is gamma, and so on...
     
  5. mytoechondriac

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    Ahh... I see, ok. I was just confused because the same topics list actually refers to the alpha carbon as the alpha carbon. THANK YOU!!
     
  6. 161927

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    For a molecule like pyridine, you could talk about electrophilic aromatic substitution at the 2 position, which means the carbon adjacent to the heteroatom. EAS would be favored there (and at the 4 position as well).
     

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