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1. |
The COSY spectrum will contain 6 diagonal peaks at the frequencies corresponding to the frequencies of the resonances in the spectrum. The spectrum will contain cross peaks at the frequencies corresponding to pairs of protons which are coupled to each other. For each coupling interaction there will be two off-diagonal cross peaks, one above and one below the diagonal. The resonances can be assigned by inspection, given the additional information in the question. Protons at C1 are at d 1.8 ppm Protons at C3 are at d 2.2 ppm Protons at C4 are at d 1.6 ppm Protons at C5 are at d 2.4 ppm Protons at C6 are at d 1.3 ppm Protons at C7 are at d 0.97 ppm |
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i) |
Sketch the COSY spectrum with 6 diagonal and 8 cross-peaks |
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ii) |
Each of the 13C resonances from protonated carbons will correlate to one proton signal. The C-H correlation will contain 6 cross peaks. |
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2. |
The COSY spectrum of 2-hexanone contains 5 diagonal peaks (corresponding to the 5 proton signals). There are 3 off-diagonal cross peaks above the diagonal and a corresponding set of 3 off-diagonal peaks below the diagonal. The strong singlet at d 1.5 ppm corresponds to the isolated CH3 at C1. The triplet resonance at d 2.0 ppm corresponds to protons at C3 (adjacent to the carbonyl group). The cross peak from the protons at d 2.0 ppm to those at d 1.3 identifies the signal at d 1.3 as the protons at C4. In turn the cross peak between the protons at C4 to those at d 1.2, identifies d 1.2 as the protons at C5. In turn the cross peak between the protons at C5 to those at d 0.8, identifies d 0.8 as the protons at C6. |
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3. |
As with the previous question, the proton spectrum can be assigned rapidly once on signal is identified because it is then possible to move progressively along the spin system (atom by atom). Protons at Ca are at d 5.5 ppm Protons at Cb are at d 4.45 ppm Protons at Cc are at d 3.25 ppm Protons at Cd/e are at d 2.8 and 4.5 ppm Each of the proton resonances correlate to one 13C resonance. The C-H correlation contains 4 cross peaks. Carbon at Ca is at d 82 ppm Carbon at Cb is at d 79 ppm Carbon at Cc is at d 19 ppm Carbon at Cd is at d 32 ppm |