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Exam
Name
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question
- Calculate the magnetic field that corresponds to the proton resonance frequency of
300.00 MHz. The gyromagnetic ratio of the
H nucleus is 26,753 s
gauss
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question
- A nucleus with an atomic number or an mass number has a nuclear
spin that can be observed by the NMR spectrometer.
A) even, odd B) odd, even C) even, even D) odd, odd
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question
- What three-word term is abbreviated NMR? 3)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question
- How many nuclear spin states are allowed for the
H nucleus?
A) 1 B) 4 C) 2 D) 3 E) 10
- The energy difference between the allowed spin states for an
H nucleus is the
strength of the external magnetic field in which it is placed.
A) exponentially related to
B) directly proportional to
C) inversely proportional to
D) logarithmically related to
E) independent of
H nuclei located near electronegative atoms tend to be relative to
H nuclei which
are not.
A) split
B) deshielded
C) resonanced
D) shielded
E) none of the above
- Electromagnetic radiation in the region is used in
H NMR
spectroscopy.
A) X-ray
B) ultraviolet
C) microwave
D) infrared
E) radio wave
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question
- is commonly used as an internal reference in NMR spectroscopy; its signal
is assigned d = 0 in
H and
C NMR spectroscopy.
- On a 90 MHz spectrometer, calculate the frequency at which a proton absorbs if it
appears at 4.20 ppm.
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question
- Using a 60 - MHz spectrometer, the protons in dichloromethane appear at 5.30 ppm. When the
same sample is placed in a 100-MHz instrument, where does the signal appear?
A) 3.
B) 8.
C) 5.
D) cannot be determined from information given
- The protons marked H a
and H b
in the molecule below are.
A) diastereotopic
B) chemically equivalent
C) enantiotopic
D) endotopic
E) none of the above
- The protons marked H
a
and H
b
in the molecule below are.
A) enantiotopic
B) diastereotopic
C) chemically equivalent
D) endotopic
E) none of the above
- The protons marked H a
and H b
in the molecule below are.
A) endotopic
B) chemically equivalent
C) enantiotopic
D) diastereotopic
E) none of the above
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
- The chair form of cyclohexane has protons in two distinct environments, axial and equatorial. When the
proton NMR of cyclohexane is run on a 100-MHz instrument at 23°C, only one signal for the compound is
observed. Explain this apparent contradiction.
- Predict the number of signals expected in the proton spin decoupled
C spectrum of 3 -
pentanone, CH
3
CH
COCH
CH
- Predict the number of signals expected in the proton spin decoupled
C spectrum of m -
dichlorobenzene (1,3-dichlorobenzene).
- Predict the number of signals expected in the proton spin decoupled
C spectrum of p -
dibromobenzene (1,4-dibromobenzene).
- Predict the number of signals expected in the proton spin decoupled
C spectrum of cyclopentane.
- Predict the number of signals expected, their splitting, and their relative area in the
H NMR spectrum
of CH
3
CH
OCH
- Predict the number of signals expected, their splitting, and their relative area in the
H NMR spectrum
of (CH 3
CCHO.
- Predict the number of signals expected, their splitting, and their relative area in the
H NMR spectrum
of 2-methylpropane (isobutane).
- Predict the number of signals expected, their splitting, and their relative area in the
H NMR spectrum
of 1,2-dichloroethane (ClCH
2
CH
Cl).
- Deduce the identity of the following compound from the
H NMR data
given. C
8
H
O: δ 3.4 (3H, singlet), 4.5 (2H, singlet), 7.2 (5H, singlet) (ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 9
H
O
: δ 2.2 (3H, singlet), 5.0 (2H, singlet), 7.2 (5H, singlet) (ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 3
H
Cl 5
: δ 4.5 (1H, triplet), 6.1 (2H, doublet) (ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 4
H
BrO: δ 2.2 (3H, singlet), 3.5 (2H, triplet), 4.5 (2H, triplet) (ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 3
H
Br 2
: δ 2.4 (2H, quintet), 3.5 (4H, triplet) (ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 5
H
O: δ 1.1 (6H, doublet), 2.2 (3H, singlet), 2.5 (1H, septet) (ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 6
H
O
: δ 3.9 (6H, singlet), 6.1 (2H, singlet) (ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 7
H
O
: δ 1.3 (6H, triplet), 3.4 (2H, singlet), 4.2 (4H, quartet) (ppm)
- Deduce the identity of the following compound from the
H NMR data given.
C
H
O: δ 1.0 (3H, triplet), 1.2-1.8 (6H, multiplet), 3.0 (1H, broad singlet), 3.8 (2H, triplet) (ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 7
H
NO
: δ 3.9 (3H, singlet), 6.9 (2H, doublet), 8.1 (2H, doublet)
(ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 8
H
O: δ 0.89 (6H, doublet), 1.87 (1H, multiplet), 3.17 (2H, doublet)
(ppm)
- Deduce the identity of the following compound from the
H NMR data
given. C 6
H
O
: δ 2.19 (3H, singlet), 2.70 (2H, singlet) (ppm)
- Deduce the identity of the following compound from the NMR data given
C
H
O
H NMR, δ 2.28 (2H, multiplet), 2.50 (2H, triplet), 4.35 (2H,
triplet);
C NMR, δ 177.81 (singlet), 68.58 (triplet), 27.70 (triplet), 22.
(triplet) (ppm)
- Deduce the identity of the following compound from the spectral data given
C
H
O
H NMR, δ 1.16 (3H, singlet), 2.21 (2H, singlet);
C NMR, δ 216.25 (singlet), 52.57 (singlet),
34.51 (triplet), 20.22 (quartet) (ppm)
- Deduce the identity of the following compound from the
C NMR data
given. C 9
H
: δ 21.3 (quartet), 127.2 (doublet), 138.0 (singlet) (ppm)
- Deduce the identity of the following compound from the
C NMR data
given. C 4
H
Br: δ 18.0 (quartet), 33.0 (triplet), 128.0 (doublet), 131.0 (doublet)
(ppm)
- Deduce the identity of the following compound from the
C NMR data
given. C 4
H
O: δ 10.0 (quartet), 22.9 (quartet), 32.0 (triplet), 69.6 (doublet)
- Deduce the identity of the following compound from the
C NMR data given.
C
H
O: δ 26.4 (quartet), 128.0 (doublet), 128.3 (doublet), 133.0 (doublet), 137.0 (singlet), 198.0 (singlet) (ppm)
- Deduce the identity of the following compound from the spectral data given
C
H
BrN:
H NMR, δ 2.98 (2H, triplet), 3.53 (2H, triplet);
C NMR, δ 21.05 (triplet), 23.87 (triplet),
118.08 (singlet) (ppm); IR, 2963, 2254 cm
- Deduce the identity of the following compound from the
H NMR data given.
C
H
N: δ 0.90 (3H, triplet), 1.07 (3H, doublet), 1.14 (2H, broad singlet), 1.34 (2H, multiplet), 2.
(1H, multiplet) (ppm)
- Deduce the identity of the following compound from the
C NMR data
given. C
6
H
O: δ 29.80 (quartet), 30.82 (singlet), 56.53 (triplet), 203.
(doublet) (ppm)
- Deduce the identity of the following compound from the
C NMR data
given. C 4
H
O: δ 11.97 (triplet), 33.54 (triplet), 67.03 (doublet) (ppm)
- Deduce the identity of the following compound from the spectral data given
C
H
O
C NMR, δ 18.06 (quartet), 45.40 (doublet), 127.32 (doublet), 127.55 (doublet), 128.61 (doublet),
139.70 (singlet) (ppm), 180.98 (singlet); IR, broad 3500-2800, 1708 cm
- Deduce the identity of the following compound from the spectral data given
C
H
O:
H NMR, δ 1.2 (6H, doublet), 2.1 (3H, singlet), 2.8 (1H, septet) (ppm); IR, 2980, 1710 cm
; MS, m/z
- Deduce the identity of the following compound from the spectral data given
C
H
H NMR, δ 1.20 (3H, triplet), 2.60 (2H, quartet), 7.12 (5H, singlet) (ppm); IR, 3050, 2970, 1600 cm
; MS,
m/z 91
- Deduce the identity of the following compound from the spectral data given
C
H
O
H NMR, δ 1.23 (3H, triplet), 2.00 (3H, singlet), 4.02 (2H, quartet) (ppm); IR, 2980, 1740 cm
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question
- What is the approximate chemical shift of an alkynyl carbon in
C NMR spectroscopy?
A) 200 ppm B) 30 ppm C) 10 ppm D) 120 ppm E) 70 ppm
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
- The
H NMR spectrum of ethanol is acquired and the hydroxyl signal appears as a singlet instead of a
triplet. Offer an explanation.
- You have a sample and its
H NMR spectrum. You know your sample contains O atoms but not N atoms,
and you suspect that your sample may be an alcohol. What common spectroscopic technique might you use
to confirm your suspicion?
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question
- If a molecule contains 4 elements of unsaturation and signals in the
H NMR spectrum
between δ
7.0 and 8.0 ppm, what structural group is likely to be present?
A) a carbon-carbon triple bond
B) an aromatic ring
C) a carbonyl group
D) a hydroxyl group
E) a cyclohexyl ring
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
- Why is carbon-carbon splitting typically not seen in
C NMR spectra?
- Deduce the identity of the compound whose molecular formula is C 8
H
from the spectral data provided:
IR (cm
H NMR (δ): 0.9 (3H, t), 1.0 (9H, s), 2.3 (2H, q) (ppm).
- Deduce the identity of the compound whose molecular formula is C 4
H
O
from the spectral data provided:
IR (cm
): 2800 - 3300 (broad), 2950, 1750;
C NMR (δ): 17.7 (q), 65.4 (q), 72.3 (d), 210.8 (s) (ppm)
- Why is carbon-hydrogen splitting not a major part of
H NMR spectra?
- Predict the number of signals expected in the proton spin decoupled
C NMR spectrum of o -
diethylbenzene (1,2-diethylbenzene).
- Predict the number of signals expected in the proton spin decoupled
C NMR spectrum of p -
diethylbenzene (1,4-diethylbenzene).
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question
- Predict the number of signals expected (disregarding splitting) in the
H NMR spectrum
of the compound shown below.
- Predict the number of signals expected in the proton spin decoupled
C NMR
spectrum of the compound shown below.
- Predict the number of distinct quartets expected in the off-resonance decoupled
C
NMR spectrum of the compound shown below.
- Predict the number of signals expected in the proton spin decoupled
C NMR
spectrum of the compound shown below.
- Predict the number of distinct quartets expected in the off-resonance decoupled
C
NMR spectrum of the compound shown below.
- Provide a structure that is consistent with the data
below.
C
H
IR (cm
H NMR ( d): 2.0 (1H, septet), 1.8 (3H, s), 0.9 (6H, d)
C NMR (d ): 78 (s), 72 (s), 45 (d), 18 (q), 15 (q)
- Provide a structure that is consistent with the data
below.
C
H
Cl
IR (cm
H NMR ( d): 1.4 (4H, t), 1.2 (4H, t)
C NMR (d ): 62 (s), 26 (t), 23 (t)
- Provide a structure that is consistent with the data
below.
C
H
O
IR (cm
H NMR ( d): 2.3 (2H, q), 1.0 (3H, t), 0.9 (9H, s)
C NMR (d ): 185 (s), 78 (s), 29 (t), 14 (q), 12 (q)
- Provide a structure that is consistent with the data
below.
C
H
O
IR (cm
H NMR ( d): 2.6 (1H, septet), 2.1 (3H, s), 1.0 (6H, d)
C NMR (d ): 195 (s), 42 (d), 18 (q), 11 (q)
- Provide a structure that is consistent with the data below.
C
H
Cl
IR (cm
H NMR ( d): 7.8 (2H, d), 7.2 (2H, d), 2.1 (3H, s)
C NMR (d ): 140 (s), 132, (s), 125 (d), 122 (d), 88 (s), 83 (s), 18 (q)
- Provide a structure that is consistent with the data
below.
C
H
O
IR (cm
): 3200 - 3600 (broad), 2950
H NMR ( d): 2.9 (1H, broad s), 1.2 (6H, q), 0.9 (9H, t)
C NMR (d ): 70 (s), 25 (t), 12 (q)
- Use the structure below to state the relationship between the indicated protons
as equivalent, enantiotopic, diastereotopic, or unrelated.
H
a
H
b
: H
a
& H
c
H
b
H
c
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question
- Any process faster than will be recorded as an average by NMR
spectroscopy.
A) 0.0005 seconds
B) 0.1 seconds
C) 0.001 seconds
D) 1 minute
E) 0.01 seconds
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question
- Using the scale below, draw the
H NMR spectrum for isobutyl acetate, shown below.
Present the peaks with correct splitting patterns and at the approximate chemical shift
0.5 ppm). Just above each peak, indicate the relative integration value of each type
of hydrogen.
- Label the different
H environments in the structure below a, b, c.. .Then complete the
table for each different type of proton. The first one is done for you as an example.
(Note: there may be fewer than 7 different proton environments)
environments a b c d e f g
chemical shift
(+/- 0.5 ppm) 1.
spin-spin splitting s
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question
- An NMR spectrometer that operates at a frequency of 60 MHz for
C NMR spectra, operates
at what frequency for
H NMR spectra?
A) 60 MHz B) 240 MHz C) 15 MHz D) 30 MHz E) 120 MHz
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question
- Compound I has a molecular formula of C
7
H
. In
C NMR , compound I gave 3
peaks and in
H NMR it also gave 3 peaks, a doublet, a triplet and a multiplet. Provide
a structure for compound I.
Answer Key
Testname: NMR
- p-nitroanisole ( p - O 2
NC
H
OCH
45) [(CH
CHCH
]
O
46) CH
COCH
CH
COCH
γ-butyrolactone
2,2-dimethylcyclopentane-1,3-dione
1,3,5-trimethylbenzene
50) CH
CH=CHCH
Br
butan- 2 - ol
acetophenone (PhCOCH
3
- BrCH 2
CH
CN
- sec - butylamine
55) (CH
CCH
CHO
cyclobutanol
PhCH(CH 3
)CO
H
58) (CH
CHCOCH
- PhCH 2
CH
60) CH
CO
CH
CH
61) E
- A fast exchange of the hydroxyl H from one ethanol molecule to another is occurring. This rapidly exchanging
H produces a single, unsplit absorption at an average field.
- Take an IR spectrum and look for the O-H stretch or add some D
2
O to the sample and reacquire the
H NMR to
see if a peak broadens or disappears.
64) B
- Only 1% of the carbon atoms are
C so the probability of two
C nuclei being adjacent is very small.
- 2,2-dimethylhex- 3 - yne
67) CH
OCH(CH
)CO
H
- Most of the carbons are
C which does not exhibit coupling to
H.
81) (CH
CHC≡CCH
Answer Key
Testname: NMR
(CH
CHCOCH
(CH
CH
COH
88) (CH
CC(CH
OH
91) B
92) D
- Hb, Jab = 10 Hz (cis), Jbc = 2 Hz (geminal)
94) H
a
& H
b
Diastereotopic H a
H
c
: Enantiotopic H
b
H
c
: Diastereotopic
95) E
- δ 3.9 ppm (d, 2H), 2.1 ppm (s, 3H), 1.9 ppm (m, 1H), 0.9 ppm (d, 6H).
