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1 | | Which of the following statements is FALSE about the NMR experiment. |
| | A) | The energy required to flip the spin of a proton is in the infrared region of the electromagnetic spectrum. |
| | B) | The energy difference between the two spin states depends on the strength of the magnetic field. |
| | C) | When energy absorption occurs, the nuclei are said to be in resonance with the electromagnetic radiation. |
| | D) | When a proton is aligned with the magnetic field, its energy is lower than when it is aligned against the magnetic field. |
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2 | | When an external magnetic field is applied, what happens to the protons in a sample? |
| | A) | All protons align with the field. |
| | B) | All protons align opposite to the field. |
| | C) | Some protons align with the field and some align opposite to it. |
| | D) | All protons assume a random orientation |
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3 | | Which of the following statements about the energy of an applied magnetic field is FALSE? |
| | A) | This energy can “flip” a proton from alignment with the field to alignment opposite the field. |
| | B) | Nuclei are “in resonance” when they absorb this energy. |
| | C) | This energy is proportional to the magnetic field strength. |
| | D) | This energy is supplied by radiation in the visible region of the spectrum. |
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4 | | Which of the following compounds has the MOST deshielded protons? |
| | A) | CH3Cl |
| | B) | CH3I |
| | C) | CH3Br |
| | D) | CH4 |
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5 | | Which of the following compounds has the MOST deshielded methyl protons? |
| | A) | tetramethylsilane |
| | B) | methyl fluoride |
| | C) | methanol |
| | D) | methylamine |
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6 | | What is the value of the chemical shift
δ for an absorption at 1800 Hz from tetramethylsilane (TMS) using an NMR spectrometer with an operating frequency of 300 MHz? |
| | A) | 1.66 ppm |
| | B) | 16.6 ppm |
| | C) | 6.0 ppm |
| | D) | 4.0 ppm |
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7 | | The chemical shift of the protons in acetone is δ2.06. How many hertz downfield from TMS will the resonance appear in a spectrum taken on a spectrometer operating at 300 MHz? |
| | A) | 300 Hz |
| | B) | 618 Hz |
| | C) | 3000 Hz |
| | D) | 6.18 x 108 Hz |
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8 | | Arrange the following compounds in order of decreasing chemical shift for the underlined hydrogens (largest δ value first, smallest value last).
CH3CH2CH3 | CH3OCH2CH3 | Cl2CHCH2CH3 | ClCH2CH2CH3 | a | b | c | d |
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| | A) | b > c > a > d |
| | B) | b > c > d > a |
| | C) | c > b > a > d |
| | D) | c > b > d > a |
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9 | | How many signals would the following molecule show in its 1H NMR spectrum? (13.0K) |
| | A) | 5 |
| | B) | 1 |
| | C) | 6 |
| | D) | 8 |
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10 | | An unknown molecule A has 4 signals in the 1H NMR spectrum. Which of the following corresponds to molecule A? |
| | A) | (11.0K) |
| | B) | (10.0K) |
| | C) | (12.0K) |
| | D) | (13.0K) |
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11 | | How many nonequivalent protons does the following structure have? (12.0K) |
| | A) | 12 |
| | B) | 8 |
| | C) | 6 |
| | D) | 4 |
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12 | | How many nonequivalent protons does the following structure have? (12.0K) |
| | A) | 6 |
| | B) | 5 |
| | C) | 4 |
| | D) | 3 |
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13 | | How many sets of protons are equivalent in meta-xylene (1,3-dimethylbenzene)? (13.0K) |
| | A) | 2 |
| | B) | 3 |
| | C) | 4 |
| | D) | 5 |
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14 | | Reading from left to right, what multiplicity would be found for the three nonequivalent sets of protons in the 1H NMR spectrum of the following compound?
(13.0K) |
| | A) | s, s, s |
| | B) | d, d, s |
| | C) | s, d, d |
| | D) | s, s, d |
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15 | | What is the splitting pattern of the methylene protons in propane? |
| | A) | triplet |
| | B) | quartet |
| | C) | doublet |
| | D) | septet |
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16 | | The signal for the methylene protons of butane is split into a |
| | A) | doublet. |
| | B) | triplet. |
| | C) | quartet. |
| | D) | quintet. |
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17 | | Give the number of lines in the coupling pattern for each type of hydrogen. (16.0K) |
| | A) | a=2, b=7, c=1, d=1 |
| | B) | a=2, b=8, c=2, d=1 |
| | C) | a=2, b=7, c=7, d=2 |
| | D) | a =2, b=8,c=8, d=2 |
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18 | | Propose a structure for the following compound. 1H NMR spectrum of C5H8O2:
δ 1.90 (multiplet, 4H)
δ2.40 (triplet, 2H)
δ 4.26 (triplet, 2H) |
| | A) | (12.0K) |
| | B) | (13.0K) |
| | C) | (12.0K) |
| | D) | (12.0K) |
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19 | | Which 1H NMR spectrum represents the following compound? (13.0K) |
| | A) | 1H NMR spectrum
δ 0.90 (quartet, 2H)
δ 2.28 (triplet, 2H)
δ 3.00 (triplet, 1H)
δ 4.50 (triplet, 1H) |
| | B) | 1H NMR spectrum
δ 1.50 (doublet, 4H)
δ 3.80 (septet, 1H)
δ 5.50 (triplet, 1H) |
| | C) | 1H NMR spectrum
δ 1.00 (triplet, 3H)
δ 1.20 (quartet, 1H)
δ 2.00 (quartet, 2H) |
| | D) | 1H NMR spectrum
δ 1.90 (quintet, 2H)
δ 2.28 (triplet, 4H) |
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20 | | An unknown compound A has the molecular formula C4H8O2. Based on the following 1H NMR spectrum, what is the structure of compound A? (21.0K) |
| | A) | (12.0K) |
| | B) | (12.0K) |
| | C) | (11.0K) |
| | D) | (12.0K) |
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21 | | The 1H NMR spectrum of a compound is shown below. What is the structure of the compound? (23.0K) |
| | A) | (14.0K) |
| | B) | (14.0K) |
| | C) | (14.0K) |
| | D) | (14.0K) |
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22 | | A compound of formula C5H12 gives 1 signal in the 1H NMR and 2 signals in the 13C NMR. The compound is |
| | A) | pentane. |
| | B) | 2-methylbutane. |
| | C) | 2,2-dimethylpropane. |
| | D) | Cannot tell without more information. |
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23 | | There are several compounds with the molecular formula C5H10Br2. Which isomer a–d with this formula has the following 1H NMR spectrum?
δ (ppm) | 1.0 (9H, singlet) | | 5.3 (1H, singlet) |
(18.0K) |
| | A) | a |
| | B) | b |
| | C) | c |
| | D) | d |
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24 | | How many methyl peaks would you expect to observe in the 1H NMR spectrum of cis-1,4-dimethylcyclohexane? |
| | A) | 1 |
| | B) | 2 |
| | C) | 3 |
| | D) | 4 |
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25 | | How many absorption bands will appear in the 13C NMR spectrum for the following compound? (14.0K) |
| | A) | 4 |
| | B) | 6 |
| | C) | 7 |
| | D) | 8 |
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26 | | How many absorption bands will appear in the 13C NMR spectrum for the following compound? (12.0K) |
| | A) | 6 |
| | B) | 7 |
| | C) | 8 |
| | D) | 9 |
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27 | | How many absorption bands will appear in the 13C NMR spectrum for the following compound? (14.0K) |
| | A) | 5 |
| | B) | 7 |
| | C) | 8 |
| | D) | 9 |
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28 | | How many resonances in the 13C NMR spectrum would the following structure show? (14.0K) |
| | A) | 8 |
| | B) | 6 |
| | C) | 4 |
| | D) | 2 |
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29 | | How many signals are expected in a 13C NMR spectrum of methylcyclohexane? |
| | A) | 4 |
| | B) | 5 |
| | C) | 6 |
| | D) | 7 |
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30 | | Deduce the structure of an unknown compound using the following 1H NMR spectrum, mass spectroscopy data, and IR spectrum. 1H NMR spectrum: δ1.30 (triplet, 6H) δ4.29 (quartet, 4H) δ 7.4–7.9 (multiplet, 4H)
Mass Spectrum: | m/e: | Intensity: (as % of base peak) | 222 | 10% | 177 | 38% | 149 | 100% |
IR Spectrum: | Intensity (peak): | Frequency (cm–1): | s | 3100 | m | 2900 | m | 2800 | s | 1740 | m-w | 1600 | m-w | 1475 | m | 1465 | m | 1450 | m | 1375 | s | 1300–1000
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| | A) | (18.0K) |
| | B) | (15.0K) |
| | C) | (13.0K) |
| | D) | (17.0K) |
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