Click on a hydrogen, spectral line, or table entry!
| Assignment | Chemical Shift (ppm) | Integration | Splitting | Coupling (Hz) | Explanation |
|---|---|---|---|---|---|
| BB | 9.22 | 1H | broad singlet | Beta is the most deshielded hydrogen because it is a substituent of a double-aromatic ring system and it is closer to nitrogen, an electronegative heteroatom, than other substituents of the system. In addition, the vector sum of the dipole moment due to the rest of the molecule is greater for beta than alpha. | |
| AA | 8.48 | 1H | singlet | Alpha is deshielded for the same reasons as beta, but has a lesser dipole moment from the rest of the molecule. | |
| Z | 7.92 | 1H | singlet | Z, X, Y, and W are part of the same double aromatic system as alpha and beta, but are not adjacent to the nitrogen, and thus are more shielded than alpha and beta. Out of these hydrogens, Z is the least shielded because it is the next closest to the nitrogen. In addition, Z is not coupled with X, Y, or W because it is on a different aromatic ring, and therefore appears as a singlet. | |
| X | 7.79 | 1H | doublet of doublets | 8.6, 1.6 | X has meta and ortho aromatic interactions (W and Y, respectively). It should therefore have coupling constants in the 0-2 and ~8 Hz ranges. This peak matches that profile and is in the aromatic range. |
| Y | 7.75 | 1H | doublet | 8.6 | Y has para and ortho aromatic interactions (W and X, respectively). It should therefore have a coupling constant in the 8 Hz range. This peak matches that profile and is in the aromatic range. |
| W | 7.61 | 1H | doublet | 5.5 | W is the last unassigned substituent of the aromatic system, and its aromatic interaction profile indicates that it should have one coupling constant lower than that for ortho interactions. W only has meta interactions, but the coupling constant was likely altered by the fact that W is a substituent of a double rather than single aromatic system. |
| B | 6.29 | 1H | doublet | 1.9 | The pi-system B is a substituent of can be conjugated into the aromatic system, which gives B a higher chemical shift than expected for hydrogen substituents of double bonds. |
| U | 6.24 | 1H | apparent singlet | U and V are part of a conjugated pi system, and therefore have a high chemical shift value. U has no neighbors, so it must appear as a singlet. | |
| V | 5.57-5.52 | 1H | multiplet | V should have a shift similar to that of U, but because V has two diastereotopic neighbors, it displays coupling. | |
| S | 4.13 | 1H | doublet | 9.0 | S is the next most deshielded hydrogen due to its position between a hydroxyl group and a conjugated pi system. In addition, it only has one neighbor, so it appears as a doublet. |
| D | 3.37 | 1H | apparent triplet | 3.37 | D and E are the next most deshielded hydrogens because they are adjacent to a double bond that is conjugated into the double aromatic system. D is less shielded than E because the inductive effects of the methyl group's electron density cannot reach it, and it is on the same side as the ring oxygen. Also note that the actual splitting pattern was not resolved in the experimental data, and was therefore listed as an apparent triplet (abbreviated "at"). |
| E | 2.75 | 1H | doublet of doublets | 11.2, 6.9 | E is more shielded than D because the electron density of the methyl group is donated to it. |
| Q | 2.61 | 1H | doublet of doublets | 9.0, 5.8 | Q is next to a hydroxyl group, and is therefore more deshielded than the remaining hydrogens. It has two neighbors with different coupling constants, and thus appears as a doublet of doublets. In addition, the coupling constant for QS must equal that of SQ. |
| G/H/O | 2.56-2.48 | 3H | multiplet | The chemical shifts of G, H, and O are similar enough such that their peaks cannot be resolved. O is deshielded by its neighboring electronegative heteroatoms while G and H are deshielded by the adjacent conjugated pi system. | |
| K/I | 2.47-2.38 | 2H | multiplet | K and I are also somewhat deshielded, though not to the degree of G, H, and O because they are near only one electronegative heteroatom and are not near a double bond. K and I are deshielded by the inductive effects of the oxygen that is on the same side of the molecule. | |
| P | 2.35 | 6H | singlet | The six hydrogens labeled as P are part of two identical methyl groups, and therefore must have an integration of 6H. Because this is the largest group of identical hydrogens in the molecule, it was assigned to the peak with the highest integration. | |
| F | 2.23 | 1H | triplet | 10.1 | F is highly shielded, but is not the most shielded hydrogen in the molecule. It is one of the substituents of a tertiary carbon, but is under the inductive effects of an oxygen. |
| L/J | 2.05-1.96 | 2H | multiplet | L and J are the substituents of the same carbons as K and I, respectively. Thier similar positioning gives them similar chemical shifts, and they are more shielded than K and I because they are on the opposite side of the molecule to the oxygen group and thus do not feel its inductive effects as strongly. | |
| M | 1.96-1.87 | 1H | multiplet | M and N are both very shielded because they are not near double bonds and the closest heteroatoms are three bonds away. Of these two hydrogens, M is less shielded because it is on the same side of the molecule as both a nitrogen and an oxygen. | |
| N | 1.76-1.68 | 1H | multiplet | N is more shielded than M because it is on the opposite side of the molecule to the nitrogen and oxygen. | |
| A | 1.15 | 3H | singlet | The three hydrogens labeled as A are part of a methyl group bonded to a tertiary carbon, and are thus highly shielded and have an integration of 3H. |