Why Aren't Splitting Patterns & Integrations for Red & Blue Protons Different?

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Discussion Overview

The discussion revolves around the splitting patterns and integrations of red and blue protons in a specific organic compound, focusing on the interpretation of NMR data. Participants explore the reasoning behind the observed patterns and the application of the n + 1 rule in determining splitting.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why the red and blue protons do not exhibit splitting patterns of "pentet, 6 H" and "octet, 4 H", respectively.
  • Another participant reflects on their confusion regarding the professor's designations of "6 H, t" and "4 H, quintet" for the red and blue protons, respectively.
  • A participant explains their reasoning, suggesting that the red protons are a triplet due to the adjacent carbons contributing 2 protons, while the blue protons form a quintet based on contributions from two adjacent carbons.
  • The explanation includes the application of the n + 1 rule, where the number of adjacent protons influences the splitting pattern.

Areas of Agreement / Disagreement

Participants express confusion and curiosity about the splitting patterns, indicating that there is no clear consensus on the interpretations of the NMR data and the reasoning behind the observed patterns.

Contextual Notes

Participants acknowledge their varying levels of expertise in organic chemistry, which may influence their interpretations and understanding of the problem.

MermaidWonders
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View attachment 8839

For the colourfully-annotated compound above, why aren't the splitting patterns and integrations for the red and blue set of protons "pentet, 6 H" and "octet, 4 H", respectively?
 

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MermaidWonders said:
For the colourfully-annotated compound above, why aren't the splitting patterns and integrations for the red and blue set of protons "pentet, 6 H" and "octet, 4 H", respectively?

Never mind. I see why.
 
MermaidWonders said:
Never mind. I see why.
I'm curious. Would you be willing to share your solution?

-Dan
 
topsquark said:
I'm curious. Would you be willing to share your solution?

-Dan

Hi,

Sorry for the super late reply. Just saw this.

When I first came across that question, I was very confused as to why my professor had put "6 H, t" and "4 H, quintet" for the splitting patterns and peak integrations for the red and blue set of protons, respectively (as in the screenshot), so I tried to look at that question in a "different" way. If we start by looking at the red protons branching out from either of the 2 carbons, we see that there are 2 protons coming off of the adjacent carbon (whether you are looking at the top or bottom adjacent carbon). Because all 6 of the red protons are chemically-equivalent, it makes sense for the splitting pattern to be a triplet according to the n + 1 rule, where n = 2 for the adjacent C. Next, if we look at the blue set of protons, we are in a similar situation. All 4 of the blue protons are chemically-equivalent, and a quintet splitting pattern comes from the fact that the "top" OR "bottom" adjacent C (the C's with red protons branching off of it) gives n = 3 AND the other adjacent C (the one with a green proton branching off of it) gives n = 1, so together, n + 1 = 4 + 1 = 5 --> quintet.

Hope what I said sort of makes sense. I'm really no expert in organic chemistry myself, but at least this is the process I had to go through to understand that solution! :(
 

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