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1. |
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i) |
The NOESY spectrum is effectively a map identifying which pairs of protons are close together in space. So in an organic molecule, NOESY will typically identify protons which are nearest neighbours (on the same or adjacent carbons) as well as protons which are constrained to be close to each other by the geometry of the molecule. |
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ii) |
The aromatic protons can be assigned by inspection - H7 has a large ortho coupling and an undetectably small para coupling so appears as a large doublet - this must be the signal at d 7.4. H6 has a large ortho coupling (about 7 Hz) a meta coupling about 1.5Hz and this must be the doublet of doublets at d 8.0. H4 has only a meta and a para coupling (no large ortho coupling) so this must be the signal at d 8.7 ppm. Note that there is also the expected NOE connectivity between H6 and H7. H4 also shows an NOE to one of the remaining doublet protons (at d 8.7) so this must be proton H3 which is close in space to H6. H2 must be the remaining proton at d 6.6. H2 and H3 also show NOE connectivity as expected. |
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2. |
The COSY spectrum of compound F permits the assignment of the protons. The protons could probably be assigned by inspection using their relative intensity and multiplicity. However the COSY can also be used. It is fairly obvious that the most downfield signal should be the proton at C2 (olefinic proton adjacent to a heteroatom) - the signal is a doublet due to coupling to the vinylic proton at C3. Once assigned, the cross-peak to the proton at d 4.9 assigns that resonance as proton at C3 and so forth. Proton at C2 are at d 6.2 ppm Proton at C3 are at d 4.9 ppm Protons at C4 are at d 2.6 ppm Protons at C5 are at d 4.2 ppm Each of the proton resonances correlate to one 13C resonance. The C-H correlation contains 4 cross peaks. Carbon at C2 is at d 145.0 ppm Carbon at C3 is at d 98.4 ppm Carbon at C4 is at d 28.5 ppm Carbon at C5 is at d 68.6 ppm |