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

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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??
 
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??

the two position is the 2nd carbon once you name the molecule..i believe.
 
the two position is the 2nd carbon once you name the molecule..i believe.

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...
 
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...

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!!
 
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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