Chapter 7 Multiple Choice Questions

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. A 1 M solution of TEMPO in chloroform at room temperature shows broader EPR spectrum than that of a 1 mM solution. Which sentence describes this phenomenon most accurately?

in the more concentrated solution, the lines are broadened due to the dipole-dipole interaction between the TEMPO molecules correct incorrect

in the more concentrated solution, the lines are broadened by the slow tumbling of TEMPO molecules correct incorrect

in the more concentrated solution, the lines are broadened due to the exchange interaction between the TEMPO molecules correct incorrect

in the more concentrated solution, the lines are broadened by the hyperfine interaction between the TEMPO molecules correct incorrect

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. Estimate the values of D and E in the spectrum of naphthalene-d₈ (Fig. 7.15)

D = 0.103 cm^-1; E = 0.015 cm^-1 correct incorrect

D = 0.103 cm^-1; E = 0.045 cm^-1 correct incorrect

D = 0.206 cm^-1; E = 0.045 cm^-1 correct incorrect

D = 0.069 cm^-1; E = 0.023 cm^-1 correct incorrect

D = 0.569 cm^-1; E = 0.093 cm^-1 correct incorrect

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. Estimate the hyperfine value for the interactions of Mn(II) nucleus with the unpaired electron in Blue-tack (EPR spectrum recorded at 9.035 GHz frequency is shown in Fig. 7.20).

260 MHz correct incorrect

15 MHz correct incorrect

523 MHz correct incorrect

1.2 MHz correct incorrect

24 MHz correct incorrect

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. Nitronyl nitroxides are stable radicals in which the unpaired electron is coupled to two equivalent nitrogen nuclei. How many lines will appear in the EPR spectrum of a solution of a rigid nitronyl nitroxide diradical with J << a?

3 lines correct incorrect

9 lines correct incorrect

5 lines correct incorrect

7 lines correct incorrect

11 lines correct incorrect

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. Nitronyl nitroxides are stable radicals in which the unpaired electron is coupled to two equivalent nitrogen nuclei. How many lines will appear in the EPR spectrum of a solution of a rigid nitronyl nitroxide diradical with J >> a?

3 lines correct incorrect

9 lines correct incorrect

5 lines correct incorrect

7 lines correct incorrect

11 lines correct incorrect

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. Estimate the position of the Δm_S = ±2 transition which would be observed in a W-band (95 GHz) EPR spectrum of a frozen solution of the diradical shown in Fig. 7.2 (X-band EPR spectra of a fluid solution of this diradical are shown in Fig. 7.3).

3390 mT correct incorrect

783 mT correct incorrect

339 mT correct incorrect

170 mT correct incorrect

1695 mT correct incorrect

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. Estimate the concentration of oxygen in an aqueous suspension of lithium phthalocyanine in water (Fig. 7.7) if the linewidth of the EPR spectrum = 0.06 mT.

13% correct incorrect

18% correct incorrect

7% correct incorrect

33% correct incorrect

23% correct incorrect

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. Which of the following metal ions cannot be used as a paramagnetic quencher?

Ti³⁺ correct incorrect

Cr³⁺ correct incorrect

Fe³⁺ correct incorrect

Zn²⁺ correct incorrect

Cu²⁺ correct incorrect

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. Estimate the value of the exchange constant J for a rigid diradical with the EPR spectrum shown in Fig. 7.3 (second spectrum from the bottom).

450 MHz correct incorrect

45 MHz correct incorrect

10 MHz correct incorrect

100 MHz correct incorrect

2 MHz correct incorrect

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. Estimate the isotropic g value for the Ni complex shown in Fig. 7.18 if the spectrum was recorded at 9.52 GHz frequency.

3.8 correct incorrect

1.3 correct incorrect

0.3 correct incorrect

4.1 correct incorrect

2.2 correct incorrect