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Shown below is the $^1$HNMR (1R, 2S)-ephedrine spectrum in ${D}_{2}O$. Maleic acid was added as an internal standard. The structure of maleic acid is shown on the bottom left, while that of (1R, 2S)-ephedrine is shown on the bottom right. Hydrogens are labeled with lower case letters.

Point out the signal from the hydroxyl proton (${H}_{f}$) and the amino proton (${H}_{c}$) in the given spectrum, respectively.

A

Hydroxyl proton (${H}_{f}$): doublet at 5.14 ppm.
Amino proton (${H}_{c}$): doublet at 1.14 ppm.

B

Hydroxyl proton (${H}_{f}$): doublet at 5.14 ppm.
Amino proton (${H}_{c}$): multiplet at 3.56 ppm.

C

Hydroxyl proton (${H}_{f}$): doublet at 3.56 ppm.
Amino proton (${H}_{c}$): doublet at 1.14 ppm.

D

Their signals are missing.

Select an assignment template