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Return to Electron Paramagnetic Resonance 1e Student Resources
Chapter 4 Multiple Choice Questions
Quiz Content
*
not completed
.
What is the hyperfine value for the nitrogen atom trapped inside a C
60
molecule? The EPR spectrum recorded at 9.5 GHz is shown in Fig. 4.2.
0.6 G
correct
incorrect
6 mT
correct
incorrect
15.7 MHz
correct
incorrect
9.5 GHz
correct
incorrect
60 mT
correct
incorrect
*
not completed
.
Predict the number of lines in the EPR spectrum of a solution of
13
C-labelled methyl radical (
13
CH
3
•), assuming the lines do not overlap.
4
correct
incorrect
3
correct
incorrect
6
correct
incorrect
24
correct
incorrect
8
correct
incorrect
*
not completed
.
Predict the number of lines in the EPR spectrum of a solution of dimethylnitroxide (CH
3
)
2
NO• assuming the lines do not overlap.
21
correct
incorrect
3
correct
incorrect
7
correct
incorrect
24
correct
incorrect
12
correct
incorrect
*
not completed
.
What is the ratio of line intensities in the EPR spectrum of the
t
-Bu radical (CH
3
)
3
C•?
1:19:36:84:126:126:84:36:19:1
correct
incorrect
1:9:36:84:126:126:84:36:9:1
correct
incorrect
1:9:35:82:120:120:82:35:9:1
correct
incorrect
1:8:28:56:70:56:28:8:1
correct
incorrect
1:10:45:120:210:252:210:120:45:10:1
correct
incorrect
*
not completed
.
Predict the hyperfine value for the EPR spectrum of fully deuteriated benzene radical anion C
6
D
6
•-
.
0.375 mT
correct
incorrect
3.75 G
correct
incorrect
2.35 mT
correct
incorrect
0.58 G
correct
incorrect
3.75 mT
correct
incorrect
*
not completed
.
Estimate the β-hyperfine value for the cyclobutyl radical (C
4
H
7
•) assuming the radical is flat and the HCH angle is 115°.
4.6 mT
correct
incorrect
27 G
correct
incorrect
5.4 mT
correct
incorrect
3.8 mT
correct
incorrect
23 G
correct
incorrect
*
not completed
.
Calculate spin density on the central carbon atom of malonic acid radical (•CH(COOH)
2
) if the hyperfine value for the α-hydrogen atom is 21.9 G.
0.95
correct
incorrect
0.85
correct
incorrect
0.15
correct
incorrect
0.65
correct
incorrect
0.23
correct
incorrect
*
not completed
.
Which one sentence explains most accurately why spin trapping is often used to detect free radical intermediates?
spin trapping provides more structural information than direct detection by EPR
correct
incorrect
spin trapping makes it easy to quantify free radical intermediates
correct
incorrect
steady state concentration of free radical intermediates is often too low to enable direct detection by EPR
correct
incorrect
detection of spin adducts requires lower power than direct detection of radical intermediates
correct
incorrect
*
not completed
.
The spectrum shown in Fig. 4.25 is composed of two ethanol radicals. Radical A shows a smaller α-hyperfine value than radical B. What is the best explanation?
radical A is less sterically shielded than radical B
correct
incorrect
radical B shows larger α-hyperfine value due to additional splitting from six γ-protons
correct
incorrect
the difference in hyperfine values is due to different dihedral angles in the two radicals
correct
incorrect
the unpaired electron in radical A is partially delocalised on the oxygen atom
correct
incorrect
*
not completed
.
Calculate the hyperfine values for TEMPO at X- and W-bands (in MHz). The spectra are shown in Fig. 4.21.
X-band: 96 MHz, W-band: 960 MHz
correct
incorrect
X-band: 48 MHz, W-band: 4.8 MHz
correct
incorrect
X-band: 48 MHz, W-band: 48 MHz
correct
incorrect
X-band: 96 MHz, W-band: 96 MHz
correct
incorrect
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