Deck 32: Spectroscopy C: Nuclear Magnetic Resonance Spectroscopy

Question 1

Which of the labeled protons absorbs furthest upfield in the ¹H NMR spectrum?

A)H_a
B)H_b
C)H_c
D)H_d

Answer 1

H_d

Question 2

How many different kinds of protons are present in each of the following compounds?

A)I = 4; II = 3; III = 1
B)I = 4; II = 4; III = 1
C)I = 4; II = 4; III = 2
D)I = 3; II = 3; III = 1

Answer 2

I = 4; II = 3; III = 1

Question 3

How many unique protons are present in each of the following compounds?

A)I = 6; II = 3; III = 6
B)I = 5; II = 4; III = 6
C)I = 6,II = 4,III = 4
D)I = 6; II = 4; III = 6

Answer 3

I = 6,II = 4,III = 4

Question 4

How many peaks would be observed for each of the circled protons in the compounds below?

A)I = 1; II = 4; III = 7
B)I = 3; II = 3; III = 7
C)I = 2; II = 4; III = 7
D)I = 2; II = 4; III = 6

Question 5

Which of the following compounds does not show only one signal in its ¹H NMR spectrum?

A)I
B)II
C)III
D)IV

Question 6

How many different kinds of protons are present in each of the following compounds?

A)I = 2; II = 4; III = 6
B)I = 2; II = 4; III = 4
C)I = 3; II = 3; III = 5
D)I = 2; II = 4; III = 5

Question 7

How many different kinds of protons are present in each of the following molecules?

A)I = 3; II = 5; III = 5; IV = 4; V = 3
B)I = 4; II = 5; III = 4; IV = 4; V = 3
C)I = 4; II = 5; III = 5; IV = 4; V = 3
D)I = 4; II = 5; III = 5; IV = 3; V = 4

Question 8

How many peaks would be observed for each of the circled protons in the compounds below?

A)I = 2; II = 6; III = 1
B)I = 3; II = 5; III = 2
C)I = 1; II = 5; III = 1
D)I = 2; II = 6; III = 2

Question 9

How many peaks would be observed for each of the circled protons in the compounds below?

A)I = 8; II = 4; III = 3; IV = 3
B)I = 7; II = 4; III = 3; IV = 4
C)I = 7; II = 3; III = 3; IV = 3
D)I = 7; II = 4; III = 2; IV = 4

Question 10

How many different kinds of protons are present in each of the following compounds?

A)I = 4; II = 4; III = 4
B)I = 4; II = 4; III = 5
C)I = 3; II = 3; III = 5
D)I = 3; II = 4; III = 5

Question 11

Which of the indicated protons would absorb furthest downfield in a ¹H NMR spectrum?

A)I
B)II
C)III
D)IV

Question 12

Into how many peaks will each of the circled protons be split? (Assume complete resolution of all NMR peaks is possible)

A)I = 3; II = 8; III = 1; IV = 4; V = 3
B)I = 9; II = 8; III = 2; IV = 4; V = 4
C)I = 4; II = 8; III = 2; IV = 4; V = 5
D)I = 4; Ii = 7; III = 2; IV = 4; V = 3

Question 13

How many different kinds of protons are present in each of the following molecules?

A)I = 6; II = 3; III = 4
B)I = 5; II = 3; III = 4
C)I = 6; II = 4; III = 5
D)I = 6; II = 4; III = 4

Question 14

How many different kinds of protons are present in each of the following compounds?

A)I = 2; II = 3; III = 4
B)I = 2; II = 3; III = 3
C)I = 3; II = 3; III = 3
D)I = 3; II = 3; III = 4

Question 15

How many peaks would be observed for each of the circled protons in the compounds below?

A)I = 6; II = 2; III = 3
B)I = 7; II = 3; III = 3
C)I = 7; II = 1; III = 3
D)I = 7; II = 2; III = 3

Question 16

Which of the indicated protons in the molecules below would absorb furthest downfield in a ¹H NMR spectrum?

A)I
B)II
C)III
D)IV

Question 17

Into how many peaks will each of the circled protons be split? (Assume complete resolution of all NMR peaks is possible)

A)I = 3; II = 7; III = 4
B)I = 2; II = 7; III = 4
C)I = 2; II = 7; III = 3
D)I = 2; II = 6; III = 4

Question 18

Which compound does not give four sets of absorptions in its ¹H NMR spectrum (i.e.,which compound does not have four unique hydrogens)?

A)I
B)II
C)III
D)IV

Question 19

How many different kinds of protons are present in each of the following compounds?

A)I = 6; II = 5; III = 3
B)I = 7; II = 5; III = 3
C)I = 7; II = 6; III = 3
D)I = 6; II = 6; III = 3

Question 20

Which of the labeled protons would absorb furthest downfield in a ¹H NMR spectrum?

A)I
B)II
C)III
D)IV

Question 21

Which of the following statements about ¹³C NMR is not true?

A)"In ¹³C proton-decoupled NMR spectra,all peaks are singlets."
B)"¹³C NMR spectra display peaks for only carbons that bear hydrogen atoms."
C)"¹³C NMR chemical shifts occur over a greater range than ¹H NMR chemical shifts."
D)"¹³C NMR easily differentiates between the different hybridized carbons (sp³,sp²,and sp hybridized carbons)."

Question 22

For each of the following compounds,indicate how many ¹³C NMR signals will be observed.

A)a: 4; b: 4; c: 7; d: 4
B)a: 5; b: 4; c: 7; d: 3
C)a: 4; b: 7; c: 7; d: 3
D)a: 5; b: 4; c: 6; d: 5

Question 23

Which of the indicated protons absorbs furthest downfield?

A)H_a
B)H_b
C)H_c
D)H_d

Question 24

What is the relationship between H_a and H_b in the following compound?

A)Homotopic
B)Enantiotopic
C)Diastereotopic
D)Mesotopic

Question 25

An unknown compound X has the molecular formula C₆H₁₂O₂.Compound X shows a strong peak in its IR spectrum at 1700 cm^-1.The ¹H NMR spectral data of compound X is given below.What is the structure of compound X?

A)I
B)II
C)III
D)IV

Question 26

What is the relationship between H_a and H_b in the following compound?

A)Homotopic
B)Enantiotopic
C)Diastereotopic
D)Mesotopic

Question 27

An unknown compound X has the molecular formula C₆H₁₄O.Compound X shows a strong peak in its IR spectrum at 3000 cm^-1.The ¹H NMR spectral data of compound X is given below.What is the structure of compound X?

A)I
B)II
C)III
D)IV

Question 28

An unknown compound X has the empirical formula C₃H₆O and a molecular ion in its mass spectrum at 116.Compound X shows no IR absorption at 3200-3600 cm^-1 but shows a peak at 1700 cm^-1.The ¹H NMR spectral data of X is shown below.What is the structure of compound X?

A)I
B)II
C)III
D)IV

Question 29

How many different kinds of protons are present in each of the following compounds?

A)a: 5; b: 6
B)a: 5; b: 5
C)a: 4; b: 6
D)a: 4; b: 5

Question 30

An unknown compound A has the molecular formula C₁₂H₁₆O.Compound A absorbs strongly in the IR at 1700 cm^-1.The NMR spectral data for compound A are given below.What is the structure of compound A?

A)I
B)II
C)III
D)IV

Question 31

What region of the electromagnetic spectrum does nuclear magnet resonance spectroscopy use?

A)Radio frequency
B)Microwave frequency
C)Infrared frequency
D)Visible frequency
E)Ultraviolet frequency

Question 32

Into how many peaks will the circled proton be split?

A)5
B)6
C)7
D)8

Question 33

An unknown compound A has the molecular formula C₇H₁₄O₂.Compound A absorbs strongly in the IR at 1700 cm^-1.The ¹H NMR spectral data for compound A are given below.What is the structure of compound A?

A)I
B)II
C)III
D)IV

Question 34

Which of the following compounds would give rise to a ¹³C spectrum with 6 peaks?

A)I
B)II
C)III
D)IV

Question 35

An unknown compound X has the molecular formula C₇H₁₃OBr.Compound X shows a strong peak in its IR spectrum at 1700 cm^-1.The ¹H NMR spectral data of compound X is given below.What is the structure of compound X?

A)I
B)II
C)III
D)IV

Question 36

An unknown compound X has the molecular formula C₁₀H₁₁O₂Br.Compound X shows a strong absorption in its IR spectrum at 1700 cm^-1.The ¹H NMR spectral data for compound X is given below.What is the structure of compound X?

A)Only I
B)Only II
C)Only III
D)I or II

Question 37

An unknown compound X has the molecular formula C₆H₁₄O.Compound X shows a peak in its IR spectrum at 3200-3600 cm^-1.The ¹H NMR spectral data for compound X is given below.What is the structure of compound X?

A)I
B)II
C)III
D)IV

Question 38

For each of the following compounds,indicate how many ¹³C NMR signals will be seen.

A)a: 3; b: 3; c: 5; d: 3
B)a: 4; b: 3; c: 5; d: 3
C)a: 3; b: 4; c: 5; d: 3
D)a: 4; b: 3; c: 3; d: 3

Question 39

How could spectroscopy be used to distinguish between the following compounds?

A)Compound A has a triplet in its ¹H NMR spectrum at 1.0 ppm.
B)Compound B has a peak at 3200-3500 cm^-1 in its IR spectrum.
C)Compound A has a peak in its IR spectrum at 2900 cm^-1.
D)Compound A has a triplet in its ¹H NMR spectrum at 1.0 ppm and compound B has a peak at 3200-3500 cm^-1 in its IR spectrum.

Question 40

Compound X has a molecular formula C₈H₁₀ and gives the ¹H NMR spectrum below.What is the structure of X?

A)A
B)B
C)C
D)D

Question 41

What effect does increasing the operating frequency of a ¹H NMR spectrum have on the value of chemical shift in Δ?

A)Chemical shift in Δ will also increase.
B)Chemical shift in Δ will decrease.
C)Chemical shift in Δ will remain the same.
D)It is not possible to predict the change in chemical shift in Δ.

Question 42

Which of the following spectroscopy methods does not involve the interaction of organic molecules with electromagnetic radiation?

A)Nuclear magnetic resonance
B)Infrared spectroscopy
C)Mass spectrometry
D)Ultraviolet spectroscopy

Question 43

How many different kinds of protons are present in the following molecule?

A)2
B)3
C)4
D)5

Question 44

An unknown compound has the formula of C₉H₁₂.The following ¹H NMR peaks were observed: Doublet at Δ 1.22
Septet at Δ 2.83
Multiplet at Δ 7.09
From the data above,pick the compound below that fits the spectra data.

A)I
B)II
C)III
D)IV

Question 45

How many different kinds of protons are present in the following molecule?

A)2
B)3
C)4
D)5

Question 46

Which of the following statements is true about electromagnetic radiation?

A)All molecules absorb electromagnetic radiation at some frequency.
B)Frequency is directly proportional to wavelength.
C)NMR uses the microwave region of the electromagnetic spectrum.
D)The radio frequency region of the electromagnetic spectrum has the largest energy per photon.
E)Energy is inversely proportional to frequency.

Question 47

How many different kinds of ¹³C peaks will be seen?

A)2
B)3
C)4
D)5

Question 48

What effect does increasing the operating frequency of a ¹H NMR spectrum have on the frequency of an absorption in Hz?

A)Frequency of an absorption in Hz will also increase.
B)Frequency of an absorption in Hz will decrease.
C)Frequency of an absorption in Hz will remain the same.
D)It is not possible to predict the change in frequency of an absorption in Hz.

Question 49

What effect does increasing the operating frequency of a ¹H NMR spectrum have on the magnitude of a coupling constant J in Hz?

A)Magnitude of coupling constant J in Hz will also increase.
B)Magnitude of coupling constant J in Hz will decrease.
C)Magnitude of coupling constant J in Hz will remain the same.
D)It is not possible to predict the change in the magnitude of coupling constant J in Hz.

Question 50

How many different kinds of ¹³C peaks will be seen?

A)2
B)3
C)4
D)5

Question 51

Which of the indicated protons absorbs further downfield?

A)H_A
B)H_B
C)H_C
D)H_D