Question

The proton NMR spectrum for a compound with the formula C₇H₁₂O₂ is shown below along with carbon-13 spectral data in tabular form. (It may be necessary to expand (zoom) some of the ¹H signals to view spin-spin splitting details.)

The infrared spectrum exhibits a strong band at 1743 cm^-1 and a medium intensity band at 1236 cm^-1.

Draw a structure for this compound.

Normal Carbon	DEPT-135	DEPT-90	Proton Shift	Relative Area
18.0	Positive	No peak	1.71	3.1
21.0	Positive	No peak	1.77	3.0
25.8	Positive	No peak	2.05	3.0
61.4	Negative	No peak	4.57	2.1
118.6	Positive	Positive	5.35	1.0
139.0	No peak	No peak
171.0	No peak	No peak

Answer 1

Formula = C7H12O2

Degree of unsaturation = 2

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1H NMR

1.71 ppm for CH3 next to alkenic carbon

1.77 ppm for CH3 next to alkenic carbon

2.04 ppm for CH3 next to C=O functionality

4.57 ppm for CH2 between Oxygen and alkenic carbon

5.35 ppm for alkenic proton

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13C NMR

18 ppm, 21 ppm and 25.8 ppm are for the three CH3 carbons

61.4 ppm is for CH2 carbon

118.6 ppm for alkenic CH carbon

139 ppm for alkenic quaternary carbon

171 ppm for C=O carbon

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Possible structure,