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The 1H NMR spectrum of an organic compound has three unique sets of peaks: a single peak, seven peaks (septet), and two peaks (doublet) - VCE - SSCE Chemistry - Question 30 - 2021 - Paper 1
Question 30
The 1H NMR spectrum of an organic compound has three unique sets of peaks: a single peak, seven peaks (septet), and two peaks (doublet). The compound is A. 3-methy... show full transcript
Worked Solution & Example Answer:The 1H NMR spectrum of an organic compound has three unique sets of peaks: a single peak, seven peaks (septet), and two peaks (doublet) - VCE - SSCE Chemistry - Question 30 - 2021 - Paper 1
Step 1
Step 2
Analyze the Septet
Answer
The septet usually indicates a proton that is adjacent to six equivalent protons. This corresponds to a (n+1) rule in NMR, where 'n' refers to how many protons are on adjacent carbons. This suggests the presence of a methyl group next to a methylene group (–CH2–) within a structure.
Step 3
Step 4
Determine the Most Likely Structure
Answer
Given that we need a compound with the aforementioned characteristics, we analyze the options provided:
- 3-methyl butanoic acid: This would analyze to potentially yield a single peak, but may not account for all peak types.
- 2-methyl propanoic acid: This compound fits well with having a septet and additional environments that match the peak counts described.
- 2-chloro-2-methylpropane: Given the presence of chlorine substituents, it may alter peak patterns.
- 1,2-dichloro-2-methylpropane: Similar reasoning as the previous, might affect the NMR.
Thus, the answer is B. 2-methyl propanoic acid.