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Multiple Choice
How many signals would be expected in the 13C NMR spectrum for the following molecule?
A
2
B
7
C
11
D
4
Verified step by step guidance
1
Identify the molecular structure: The molecule shown is 2,2,4,4-tetramethylpentan-3-one, also known as pinacolone.
Determine the symmetry of the molecule: The molecule has a plane of symmetry that divides it into two identical halves.
Identify unique carbon environments: Due to the symmetry, carbons in equivalent environments will give the same signal in the 13C NMR spectrum.
Count the unique carbon environments: There are four unique carbon environments in this molecule: the carbonyl carbon, the two equivalent methyl groups on each side of the carbonyl, and the central carbon connected to the carbonyl.
Conclude the number of signals: Based on the unique carbon environments, the 13C NMR spectrum will show four distinct signals.