OpenStax Organic Chemistry: A Tenth Edition Student Solutions Manual
Chapter 13 – Structure Determination: Nuclear Magnetic Resonance Spectroscopy
Solutions to Problems
13.1
1.20 10−4 kJ/mol
E=
λ(in m)
c 3.0 108 m/s
λ= = ; v = 187 MHz = 1.87 108 Hz
v v
3.0 108 m/s
λ= = 1.60 m
1.87 108 Hz
1.20 10−4 kJ/mol
E= = 7.5 10−5 kJ/mol
1.60
Compare this value with E = 8.0 × 10–5 kJ/mol for 1H (given in the text). It takes slightly
less energy to spin-flip a 19F nucleus than to spin-flip a 1H nucleus.
13.2
c 3.0 108 m/s
λ= = ; v = 300 MHz = 3.0 108 Hz
v v
3.0 10 m/s
8
λ= = 1.0 m
3.0 108 Hz
1.20 10−4 kJ/mol
E= = 1.20 10−4 kJ/mol
1.0
Increasing the spectrometer frequency from 200 MHz to 300 MHz increases the amount of
energy needed for resonance.
13.3
2- Chloropropene has three kinds of protons. Protons b and c differ because one is cis to the
chlorine and the other is trans.
Observed chemical shift (in Hz)
13.4 δ =
200 MHz
1454 Hz 610 Hz
(a) δ = = 7.27 δ for CHCl3 (b) δ = = 3.05 δ for CH3Cl
200 MHz 200 MHz
693 Hz 1060 Hz
(c) δ = = 3.46 δ for CH3OH (d) δ = = 5.30 δ for CH 2 Cl2
200 MHz 200 MHz
1 1/4/2024
, OpenStax Organic Chemistry: A Tenth Edition Student Solutions Manual
13.5 (a)
Observed chemical shift (#Hz away from TMS)
δ=
Spectrometer frequency in MHz
Units of δ are parts per million. In this problem, δ = 2.1 ppm
Observed chemical shift
2.1 ppm =
200 (MHz)
420 Hz = Observed chemical shift
(b) If the 1H NMR spectrum of acetone were recorded at 500 MHz, the position of
absorption would still be 2.1 δ because measurements given in ppm or δ units
are independent of the operating frequency of the NMR spectrometer.
Observed chemical shift
(c) 2.1 δ = ; Observed chemical shift = 1050 Hz
500 (MHz)
13.6
(a) 1.2–1.6 δ
(b) 2.0–2.4 δ
(c) 6.5–8.0 δ
(d) 2.5–4.0 δ
(e) 9.7–10.0 δ
(f) 1.0–3.0 δ
13.7
Proton δ Kind of proton
1 1.0 primary alkyl
2 1.8 allylic
3 6.1 vinylic
4 6.3 vinylic (different from
proton 3)
5 7.2 aromatic
6 6.8 aromatic
7 3.8 ether
This compound has seven different kinds of protons. Notice that the two protons labeled 5 are
equivalent, as are the two protons labeled 6 because of rotation around the bond joining the
aromatic ring and the alkenyl side chain.
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, OpenStax Organic Chemistry: A Tenth Edition Student Solutions Manual
13.8
There are two absorptions in the 1H NMR spectrum of p–xylene. The four ring protons
absorb at 7.05 δ, and the six methyl-group protons absorb at 2.23 δ. The peak ratio of
methyl protons:ring protons is 3:2.
13.9
Number of
Compound Protons Adjacent Protons Splitting
(a) 1 3 quartet
2 1 doublet
(b) 1 0 singlet
2 2 triplet
3 2 triplet
(c) 1 2 triplet
2 4 quintet
(d) 1 1 doublet
2 6 septet
3 3 quartet
4 2 triplet
(e) 1 2 triplet
2 3 quartet
3 6 septet
4 1 doublet
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Chapter 13 – Structure Determination: Nuclear Magnetic Resonance Spectroscopy
Solutions to Problems
13.1
1.20 10−4 kJ/mol
E=
λ(in m)
c 3.0 108 m/s
λ= = ; v = 187 MHz = 1.87 108 Hz
v v
3.0 108 m/s
λ= = 1.60 m
1.87 108 Hz
1.20 10−4 kJ/mol
E= = 7.5 10−5 kJ/mol
1.60
Compare this value with E = 8.0 × 10–5 kJ/mol for 1H (given in the text). It takes slightly
less energy to spin-flip a 19F nucleus than to spin-flip a 1H nucleus.
13.2
c 3.0 108 m/s
λ= = ; v = 300 MHz = 3.0 108 Hz
v v
3.0 10 m/s
8
λ= = 1.0 m
3.0 108 Hz
1.20 10−4 kJ/mol
E= = 1.20 10−4 kJ/mol
1.0
Increasing the spectrometer frequency from 200 MHz to 300 MHz increases the amount of
energy needed for resonance.
13.3
2- Chloropropene has three kinds of protons. Protons b and c differ because one is cis to the
chlorine and the other is trans.
Observed chemical shift (in Hz)
13.4 δ =
200 MHz
1454 Hz 610 Hz
(a) δ = = 7.27 δ for CHCl3 (b) δ = = 3.05 δ for CH3Cl
200 MHz 200 MHz
693 Hz 1060 Hz
(c) δ = = 3.46 δ for CH3OH (d) δ = = 5.30 δ for CH 2 Cl2
200 MHz 200 MHz
1 1/4/2024
, OpenStax Organic Chemistry: A Tenth Edition Student Solutions Manual
13.5 (a)
Observed chemical shift (#Hz away from TMS)
δ=
Spectrometer frequency in MHz
Units of δ are parts per million. In this problem, δ = 2.1 ppm
Observed chemical shift
2.1 ppm =
200 (MHz)
420 Hz = Observed chemical shift
(b) If the 1H NMR spectrum of acetone were recorded at 500 MHz, the position of
absorption would still be 2.1 δ because measurements given in ppm or δ units
are independent of the operating frequency of the NMR spectrometer.
Observed chemical shift
(c) 2.1 δ = ; Observed chemical shift = 1050 Hz
500 (MHz)
13.6
(a) 1.2–1.6 δ
(b) 2.0–2.4 δ
(c) 6.5–8.0 δ
(d) 2.5–4.0 δ
(e) 9.7–10.0 δ
(f) 1.0–3.0 δ
13.7
Proton δ Kind of proton
1 1.0 primary alkyl
2 1.8 allylic
3 6.1 vinylic
4 6.3 vinylic (different from
proton 3)
5 7.2 aromatic
6 6.8 aromatic
7 3.8 ether
This compound has seven different kinds of protons. Notice that the two protons labeled 5 are
equivalent, as are the two protons labeled 6 because of rotation around the bond joining the
aromatic ring and the alkenyl side chain.
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, OpenStax Organic Chemistry: A Tenth Edition Student Solutions Manual
13.8
There are two absorptions in the 1H NMR spectrum of p–xylene. The four ring protons
absorb at 7.05 δ, and the six methyl-group protons absorb at 2.23 δ. The peak ratio of
methyl protons:ring protons is 3:2.
13.9
Number of
Compound Protons Adjacent Protons Splitting
(a) 1 3 quartet
2 1 doublet
(b) 1 0 singlet
2 2 triplet
3 2 triplet
(c) 1 2 triplet
2 4 quintet
(d) 1 1 doublet
2 6 septet
3 3 quartet
4 2 triplet
(e) 1 2 triplet
2 3 quartet
3 6 septet
4 1 doublet
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