Deck 14: Nuclear Magnetic Resonance Spectroscopy

Question 1

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.

Answer 1

I = 2; II = 4; III = 5.

Question 2

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.

Answer 2

I = 7; II = 4; III = 3; IV = 4.

Question 3

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 3

H_d

Question 4

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

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

Question 5

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 6

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.

Question 7

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 8

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 9

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 10

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 11

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 12

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.

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

Into how many peaks will each of the circled protons be split?

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 15

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 16

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 17

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 18

Into how many peaks will each of the circled protons be split?

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 19

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

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

Question 20

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 21

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 22

Which of the indicated protons absorbs furthest downfield?

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

Question 23

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 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 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 26

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 27

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 28

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 29

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 30

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 31

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 32

Into how many peaks will the circled proton be split?

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

Question 33

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

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

Question 34

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 35

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 36

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

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

Question 37

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 38

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 39

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 40

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 41

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 spectroscopy
D) Ultraviolet spectroscopy

Question 42

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

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

Question 43

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.