Consider the following molecule - VCE - SSCE Chemistry - Question 16 - 2023 - Paper 1
Question 16
Consider the following molecule.
How many peaks will be observed in a $^{13}C$ NMR spectrum of this molecule?
A. 5
B. 6
C. 7
D. 8
Worked Solution & Example Answer:Consider the following molecule - VCE - SSCE Chemistry - Question 16 - 2023 - Paper 1
Step 1
Determine the distinct carbon environments
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Answer
To find the number of peaks in a 13C NMR spectrum, we need to identify the different carbon environments within the molecule. Each type of carbon environment will correspond to a distinct peak in the NMR spectrum.
Step 2
Analyze the molecule structure
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Answer
The provided molecule contains an ester group and different carbon chains. By examining the structural formula, we will count the unique types of carbon:
The carbonyl carbon (C=O) is one unique environment.
There are two methylene (–CH2) groups that are equivalent, offering one peak together.
Additionally, there are two terminal methyl (–CH3) groups, which are also equivalent, contributing one peak.
Finally, the carbon adjacent to the carbonyl (–C) will be another unique environment.
Summarizing these, we find:
1 peak for the carbonyl carbon,
1 peak for the equivalent methylene group,
1 peak for the equivalent methyl groups,
1 peak for the adjacent carbon.
Thus, we have a total of 6 distinct carbon environments.
Step 3
Conclusion
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Answer
Based on our analysis, the number of peaks observed in the 13C NMR spectrum of this molecule is 6, corresponding to option B.
