By: Kirill Levin
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Figure 1: Aspartic acid’s (C4H7NO4) molecular structure is represented above. It is one of the 11 non-essential amino acids and one of the 20 overall. This compound has carboxylic acid groups (COOH) on either side, as well as a single amino group (NH2).


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Figure 2: Overall H-NMR spectrum of Aspartic Acid.

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Figure 3: The first visible peak, staring from the right of the spectrum, is located at ~0 ppm and is caused by tetramethylsilane (TMS) which is used as an internal standard.

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Figure 4: This is a doublet of doublets from one of the methylene hydrogens coupling with the other methylene hydrogen (made different because of the chiral center) and the adjacent CH (thanks to Don Clarke for pointing out)

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Figure 5:
This is a doublet of doublets from one of the methylene hydrogens coupling with the other methylene hydrogen (made different because of the chiral center) and the adjacent CH (thanks to Don Clarke for pointing out)


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Figure 6: A doublet of doublets is visible between ~3.86 ppm and ~3.90 ppm. These 4 peaks are a result of the coupling of the single H of the CHNH2 group with the CH2 group between the COOH and CHNH2 groups. As previously mentioned the presence of a chiral center makes the H’s of the CH2 group unequal and causes the single H of the CHNH2 group to couple with each H separately. The doublet of doublets is present within the 3-4 ppm range because of the bond with the N of the NH2 group.

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Figure 7: The final visible peak at ~4.8ppm accounts for the solvent used, deuterium oxide (D2O). D2O had a large effect on the spectrum because it prevented the visibility of the peaks from the H’s of the NH2 and OH groups.