Lower Number Carbon VS Higher Number Carbon

[Doctor of JiJi]

Hi, what is considered a lower number carbon or higher number carbon? Is the lower number carbon away from alpha carbon? such as 1 is higher nubmer carbon and 6 is lower number carbon?

For example, in a cyclic sugar formation in which the OH group attack the carbonyl carbon, is the OH attached to a higher number carbon or lower number carbon? I always thought the bigger the number the higher the carbon number such as the OH attaches to the higher number carbon but Kaplan says the opposite. Can anyone explain?

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[Cornfed101]

What is the significance of knowing “higher” vs “lower”? I’ve never heard of that in all my MCAT studying nor was it on the actual test. I have seen them ask about specific numbers of the carbon though. Just not really sure what your question is...

 

[Doctor of JiJi]

What is the significance of knowing “higher” vs “lower”? I’ve never heard of that in all my MCAT studying nor was it on the actual test. I have seen them ask about specific numbers of the carbon though. Just not really sure what your question is...

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One of the Kaplan full-length questions asks this. The correct answer is like the functional group of lower number carbon is the nucleophilic reactant in the cyclic sugar formation. I chose higher number because the OH is attached to 5th carbon I thought it is higher number but it is wrong. I never heard of the higher or lower number either so I am confused.

 

[Cornfed101]

One of the Kaplan full-length questions asks this. The correct answer is like the functional group of lower number carbon is the nucleophilic reactant in the cyclic sugar formation. I chose higher number because the OH is attached to 5th carbon I thought it is higher number but it is wrong. I never heard of the higher or lower number either so I am confused.

In this context, I would think about it looking at a Fischer diagram. "Higher" meaning towards the top. This just seems like a naming convention that you need to be familiar with, but I have never seen any AAMC questions refer to this.

 

[Doctor of JiJi]

In this context, I would think about it looking at a Fischer diagram. "Higher" meaning towards the top. This just seems like a naming convention that you need to be familiar with, but I have never seen any AAMC questions refer to this.

Oh, that makes sense. Thanks