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1. |
The 1H NMR spectrum of the borohydride ion (BH4-) is given below. The element boron has two isotopes, both of which are NMR active : 10B (I=3, 20%) and 11B (I=3/2, 80%). Rationalise the appearance of the observed 1H spectrum.
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2. |
The 1H NMR spectrum of methane (CH4) consists of a single resonance and because the four protons have exactly the same chemical shift, no H-H couplings appear in the spectrum so it is not possible to measure 2JH-H from the spectrum. The 1H NMR spectrum of dideuteromethane (CD2H2) is given below. Rationalise the splitting pattern and explain how you could estimate 2JH-H using this spectrum.
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3. |
The 1H NMR spectrum of propane consists of two signals (d 0.90 and d 1.30) with areas in the ratio 3:1 respectively. Sketch the 1H spectrum of propane (to scale) for three different spectrometers with proton frequencies of 60 MHz, 300 MHz and 600 MHz. Answer |
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4. |
The 1H NMR spectrum of dipropylether, (CH3CH2CH2)2O, is given below. The spectrum consists of 3 distinct resonances at d 3.4 (2H, triplet), d 1.6 (2H, multiplet) and d 1.0 (3H, triplet). Assign the spectrum and clearly describe the spectra which would be obtained while applying a strong Rf field at : |
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i) d 3.4 ppm. |
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ii) d 1.6 ppm. |
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iii) d 1.0 ppm.
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