Answer
Answer
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1. |
The aromatic region of the 1H NMR spectrum of N-methyl-2,4,6-trinitroaniline is shown below, recorded at a number of different temperatures. Rationalise the appearance of the spectra in terms of a reasonable exchange process in this molecule. Answer |
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2. |
The 1H NMR spectrum of 1,4-dioxan-d7 at room temperature consists of a singlet (with broadband decoupling of 2H). At -150oC the spectrum appears as two singlets of equal intensity. Using your knowledge about the conformation (and conformational mobility) of 6-membered rings, give a rationalisation as to why the room temperature and low temperature spectra appear as they do. Answer |
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3. |
The intensity of the 1H NMR signal is determined in part by the population difference between the a and b states, does the sensitivity of the experiment increase, decrease or stay the same when : |
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i) |
The strength of the magnet is increased. |
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ii) |
The temperature of the sample is increased. |
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iii) |
2H was observed instead of 1H. |
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iv) |
A sample of 10 mm diameter is used instead of 5 mm. |
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v) |
The concentration of the sample is increased. |
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4. |
What would happen to the widths of the 1H NMR signal in a sample of CH3Br when : |
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i) |
A soluble Fe(III) salt was added to the solution. |
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ii) |
The solution was scrupulously deoxygenated before the spectrum was acquired. |
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iii) |
The solution was cooled to near its freezing point. |
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