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

[mytoechondriac]

---

Members do not see this ad.

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??

 

[RySerr21]

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.

 

[nfg05]

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...

 

[mytoechondriac]

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!!

 

[161927]

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).