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Table
| Assignment | δ (ppm) | Integration | Splitting | J (Hz) |
|---|---|---|---|---|
| 1 | 0.30-0.16 | 3H | m | N/A |
| 2 | 0.71-0.48 | 6H | m | N/A |
| 3 | 0.88 | 3H | dd | 14.1, 7.6 |
| 4 | 1.33-1.11 | 9H | m | N/A |
| 5 | 1.66-1.49 | 6H | m | N/A |
| 6 | 1.96-1.74 | 8H | m | N/A |
| 7 | 2.05 | 4H | d | 11.5 |
| 8 | 2.25-2.13 | 2H | m | N/A |
| 9 | 2.65 | 2H | ddd | 14.1, 4.7, 1.6 |
| 10 | 2.89 | 1H | dd | 14.4, 5.4 |
| 11 | 3.70-3.59 | 6H | qt | 6.9, 1.8 |
| 12 | 3.89 | 1H | br s | N/A |
| 13 | 4.06-3.95 | 2H | m | N/A |
| 14 | 4.18 | 1H | s | N/A |
| 15 | 4.24 | 2H | s | N/A |
| 16 | 4.54 | 3H | dd | 11.4, 1.6 |
| 17 | 4.79-4.70 | 6H | s | N/A |
| 18 | 5.02 | 3H | d | 11.4 |
Explanations
1: These hydrogens, a methyl at the end of an ethoxy group, should be a relatively shielded triplet with integration 3H. As there were no documented triplets in this spectrum, we chose the most upfield peak with integration 3H.
2: See “Unassigned.”
3: These hydrogens are relatively deshielded due to a nearby oxygen and should have a more complex splitting pattern than those that appeared in the spectrum. Thus, this peak, as well as (9), (16), and (18) were mostly assigned on the basis of ppm shift and coupling constants. Although the integration of 3H does not conform to the number of hydrogens assigned to this peak, 2, there was no other appropriate peak for the very shielded pair of hydrogens neighboring (9) on the right side of the molecule.
4: See “unassigned.”
5: See “unassigned.”
6: See “unassigned.”
7: These hydrogens, while not enantiotopic, are relatively shielded in the cyclopropane and are each others’ neighbors. Hence, all 4 were assigned to this 4H integration peak with a doublet.
8: This pair of hydrogens with integration 2H and an expected splitting pattern of triplet were assigned to this peak through process of elimination, as the other 2H peaks were too downfield, such as (15), or had incorrect splitting patterns, such as (9).
9: Even farther away from oxygens, hydrogens (9) are neighbors with (16) and (3) through coupling constants J = 1.6 and 14.1, respectively, conforming to the assigned structure.
10: This hydrogen, conforming to the 1H integration and doublet of doublet splitting pattern, is adjacent to an alcohol and thus is more deshielded than other hydrogens, such as (7).
11: These (apparently six) hydrogens display a complex splitting pattern (quartet of triplets) that theoretically should not exist in the molecule. Hence, they were assigned to the 4 remaining neighboring hydrogens that had not yet been assigned.
12: Hydrogens in alcohols typically have broad singlet peaks, this one being the only that matches said description.
13: These hydrogens form a singlet, are enantiotopic, and very deshielded due to a neighboring ester. Since there are two and they share similar environments, this is what lead us to place them in the same 2H singlet peak.
14: The only other singlet that should be in the molecule besides those in (5), deshielded by a nearby oxygen.
15: These hydrogens have no three-bond neighbors and are deshielded by close oxygens, hence they should be singlets.
16: More shielded than (18) due to distance away from oxygens, these hydrogens, despite not conforming to splitting patterns like (18), should have more complex splitting due to more neighbors (dd) than (18), with which it shares J = 11.4 due to neighbors.
17: See “unassigned.”
18: The coupling constant J = 11.4 is shared with peak (16), so those hydrogens are neighbors.
Unassigned: As molecules get more complicated, 1H NMR spectra can get harder to interpret because of overlapping peaks. According to the integrations given in the paper the NMR detected over double the appropriate amount of hydrogens from this molecule. Thus, drastic decisions had to be made as to which peaks to ignore. The region between 1-2 ppm, where many peaks are often found, was abundant with several high-integration peaks, made more ambiguous by their assignment as multiplets. As such, these high integration (>6H) vague peaks were not assigned.