8.* (1994 2 2) Three regioisomers ("constitutional isomers") X, Y, Z of an aromatic hydrocarbon have the molecular formula: C8H10. The 1H NMR spectrum of hydrocarbon X exhibits two sharp singlets in a ratio of 2:3 (integrated intensities) (no spin-coupling was observed). The 13C NMR spectrum of X shows three singlets (ignore possible spin-coupling with H). Similarly, the NMR spectra of Y and Z show the pattern of H and C signals given below. The ratios of integrated intensities for the H signals are given in parenthesis.


Number of H signals (ratios)

Number of C signals


2 (2:3)



3 (3:1:1)



4 (6:2:1:1)


On the basis of these data, write structural formulas for X, Y, and Z.

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9.* (1993 F 3) A quote from the San Francisco Chronicle 11/25/93 "The traditional Thanksgiving menu contains roast turkey with all the trimmings--nuts, cranberry sauce, sweet potatoes and pumpkin pie--and a dash of aflatoxins, nitrates and malonaldehyde". The article goes on to say that several toxins which have been found to cause cancer occur in minuscule, harmless amounts in such a meal. If we treat our holiday dinner the same way we do Alar and other pesticide residues, the Thanksgiving meal would be banned. It makes more of a difference how much you eat than what you eat; eating 3.8 tons of such a meal could mutate your genes. Some people strongly disagree with this viewpoint.

Among the toxins mentioned were: aflatoxin (from mixed nuts), eugenol (in the cranberry sauce) and malonaldehyde (from the turkey).

A structural formula for eugenol is shown below.

A. What is the origin of the suffix of this name?

B. How many stereoisomers exist for eugenol?

C. How many different 13C NMR signals would you expect in the 13C NMR spectrum of eugenol (ignore spin coupling)?

D. How many sites of unsaturation are in eugenol?

Malonaldehyde is also called "propandial".

E. Write a structural formula for malonaldehyde.

F. Sketch the expected proton NMR spectrum for malonaldehyde; include relative chemical shifts from tetramethylsilane (show its signal) and indicate the spin coupling pattern. Assign the peaks to each type of protons.

The carcinogen formaldehyde, CH2O, is also in the apples (derived from the apple skin).

G. Sketch the expected proton NMR spectrum of monodeuteroformaldehyde, CHDO, show the spin coupling. Hint: D has a nuclear spin of 1.

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10.* (1993 2 4)

A. Sketch the 1H NMR spectrum you expect for diethylcarbonate. Show spin coupling patterns, including the expected ratio of peak heights.

B. How would the spectrum be different with a spectrometer which had twice the magnetic field strength?

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11.* (1990 F 3) Explain what the 1H and 13C NMR spectra of napthalene would look like. In the 13C NMR consider only the coupling between adjacent atoms. In the 1H NMR consider coupling through no more than 3 bonds.

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