Deck 16: Nuclear Magnetic Resonance Spectroscopy

Question 1

Protons H_a and H_b in the following compound are _________.

A) homotopic
B) enantiotopic
C) diastereotopic
D) mesotopic
E) none of these

Answer 1

diastereotopic

Question 2

Which of the following can not be probed by an NMR spectrometer?

A) nucleus with odd number of protons & odd number of neutrons
B) nucleus with odd number of protons &even number of neutrons
C) nucleus with even number of protons & odd number of neutrons
D) nucleus with even number of protons & even number of neutrons
E) none of these

Answer 2

nucleus with even number of protons & even number of neutrons

Question 3

Protons H_a and H_b in the following compound are _________.

A) homotopic
B) enantiotopic
C) diastereotopic
D) mesotopic
E) none of these

Answer 3

enantiotopic

Question 4

Protons H_a and H_b in the following compound are _________.

A) homotopic
B) enantiotopic
C) diastereotopic
D) mesotopic
E) none of these

Question 5

Protons H_a and H_b in the following compound are _________.

A) homotopic
B) enantiotopic
C) diastereotopic
D) mesotopic
E) none of these

Question 6

The strength of the magnetic field is a determining factor for the range of _______that must be used for NMR spectrometer.

A) temperature
B) frequencies
C) tesla
D) spin states
E) none of these

Question 7

_______ protons experience a net magnetic field strength that is higher than the _____ protons.

A) Deshielded, shielded
B) Shielded, deshielded
C) Paramagnetic, diamagnetic
D) Shielded, diamagnetic
E) none of these

Question 8

How many nuclear spin states are possible for the ¹H nucleus?

A) 1
B) 2
C) 4
D) 5
E) none of these

Question 9

Protons H_a and H_b in the following compound are _________.

A) homotopic
B) enantiotopic
C) diastereotopic
D) mesotopic
E) none of these

Question 10

Which of the following type of protons are chemically equivalent?

A) homotopic
B) enantiotopic
C) diastereotopic
D) A & B
E) B & C

Question 11

Protons H_a and H_b in the following compound are _________.

A) homotopic
B) enantiotopic
C) diastereotopic
D) mesotopic
E) none of these

Question 12

Which of the following type of protons are chemically non-equivalent?

A) homotopic
B) enantiotopic
C) diastereotopic
D) A & B
E) B & C

Question 13

Which of the following is true about the location of signals in a ¹H NMR spectrum?

A) it indicates the number of neighboring protons
B) it indicates the electronic environment of neighboring protons
C) it indicates the number of different protons
D) it indicates the electronic environment of absorbing protons
E) it indicates the number of protons in the signal

Question 14

Which of the following is true about the shape (multiplicity) of the signal in a ¹H NMR spectrum?

A) it indicates the number of neighboring protons
B) it indicates the electronic environment of neighboring protons
C) it indicates the number of different protons
D) it indicates the electronic environment of absorbing protons
E) it indicates the number of protons in the signal

Question 15

Which of the following is true about the area under each signal in a ¹H NMR spectrum?

A) it indicates the number of neighboring protons
B) it indicates the electronic environment of neighboring protons
C) it indicates the number of different protons
D) it indicates the electronic environment of absorbing protons
E) it indicates the relative number of protons in the signal

Question 16

Which of the following is not a common solvent used for acquiring a ¹H NMR spectrum?

A) CDCl₃
B) CCl₄
C) CD₃CN
D) CH₃OH
E) D₂O

Question 17

Which of the following electromagnetic radiation is used in NMR spectroscopy?

A) UV
B) IR
C) visible
D) $\gamma$ -rays
E) radio wave

Question 18

Which of the following is true about the relationship between the energy gap ( $\Delta$ E) between the spin states for a ¹H nucleus and the strength of the external magnetic field?.

A) they are inversely proportional
B) they are directly proportional
C) there is no relationship
D) the magnetic field is slightly less
E) none of these

Question 19

Which of the following is true about the number of signals in a ¹H NMR spectrum?

A) it indicates the number of neighboring protons
B) it indicates the electronic environment of neighboring protons
C) it indicates the number of different kinds of protons
D) it indicates the electronic environment of absorbing protons
E) it indicates the number of protons in the signal

Question 20

_______ protons experience a net magnetic field strength that is smaller than the applied magnetic field.

A) Deshielded
B) Shielded
C) Paramagnetic
D) Diamagnetic
E) none of these

Question 21

How many signals would you expect in the ¹H NMR spectrum of CH₃OCH₂CH₂OCH₃?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 22

How many signals would you expect in the ¹H NMR spectrum of the following compound?

A) 4
B) 5
C) 6
D) 7
E) 8

Question 23

How many signals would you expect in the ¹H NMR spectrum of (CH₃)₂CHCH₂CH₂CH₃?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 24

Protons H_a and H_b in the following compound are _________.

A) homotopic
B) enantiotopic
C) diastereotopic
D) mesotopic
E) none of these

Question 25

How many signals would you expect in the ¹H NMR spectrum of the following compound?

Question 26

Which of the following is the best prediction of the chemical shifts for the signals in the ¹H NMR spectrum for the following compound?

A) I=3.9 ppm, II=4.2 ppm, III=2.2 ppm, IV=3.4 ppm
B) I=3.4 ppm, II=2.2 ppm, III=2.2 ppm, IV=3.4 ppm
C) I=3.4 ppm, II=2.2 ppm, III=4.2 ppm, IV=3.4 ppm
D) I=3.4 ppm, II=4.2 ppm, III=4.2 ppm, IV=3.4 ppm
E) none of these

Question 27

Which of the indicated protons in the following compound would appear most downfield in the ¹H NMR spectrum?

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

Question 28

How many signals would you expect in the ¹H NMR spectrum of the following compound?

A) 4
B) 5
C) 6
D) 7
E) 8

Question 29

Which of the indicated protons in the following compound would appear most downfield in the ¹H NMR spectrum?

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

Question 30

How many signals would you expect in the ¹H NMR spectrum of HOCH₂CH₂CH₂CH₂OH?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 31

Which of the following is the best prediction of the chemical shifts for the signals in the ¹H NMR spectrum for the following compound?

A) I=0.9 ppm, II=2.7 ppm, III=1.2 ppm, IV=0.9 ppm
B) I=1.1 ppm, II=3.2 ppm, III=1.4 ppm, IV=0.9 ppm
C) I=0.9 ppm, II=1.7 ppm, III=1.2 ppm, IV=1.1 ppm
D) I=0.9 ppm, II=1.9 ppm, III=3.4 ppm, IV=0.9 ppm
E) none of these

Question 32

How many signals would you expect in the ¹H NMR spectrum of the following compound?

A) 4
B) 5
C) 6
D) 7
E) 9

Question 33

Which of the following is the best prediction of the chemical shifts for the signals in the ¹H NMR spectrum for the following compound?

A) I=3.7 ppm, II=2.7 ppm, III=1.9 ppm
B) I=3.7 ppm, II=2.2 ppm, III=1.9 ppm
C) I=3.9 ppm, II=2.7 ppm, III=1.9 ppm
D) I=3.9 ppm, II=2.2 ppm, III=2.4 ppm
E) none of these

Question 34

Protons H_a and H_b in the following compound are _________.

A) homotopic
B) enantiotopic
C) diastereotopic
D) mesotopic
E) none of these

Question 35

______is used as a reference for recording NMR spectra and is assigned a chemical shift value of zero.

Question 36

Which of the indicated protons in the following compound would appear most upfield in the ¹H NMR spectrum?

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

Question 37

How many signals would you expect in the ¹H NMR spectrum of the following compound?

Question 38

How many signals would you expect in the ¹H NMR spectrum of CH₃OCH₂CH₃?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 39

How many signals would you expect in the ¹H NMR spectrum of the following compound?

Question 40

Which of the following is the best prediction of the chemical shifts for the signals in the ¹H NMR spectrum for the following compound?

A) I=0.9 ppm, II=1.7 ppm, III=3.9 ppm, IV=2.4 ppm
B) I=0.9 ppm, II=1.2 ppm, III=3.7 ppm, IV=1.9 ppm
C) I=0.9 ppm, II=1.7 ppm, III=3.4 ppm, IV=2.4 ppm
D) I=0.9 ppm, II=1.7 ppm, III=3.4 ppm, IV=1.9 ppm
E) none of these

Question 41

Determine the multiplicity of each signal in the expected ¹H NMR spectrum of the following compound.

Question 42

Determine the multiplicity of each signal in the expected ¹H NMR spectrum of the following compound.

Question 43

Predict the chemical shifts for the signals in the ¹H NMR spectrum for the following compound.

Question 44

Which of the following is the maximum multiplicity observed for H_b protons in the following compound? Assume that J_ab and J_bc values are different.

A) 9
B) 12
C) 21
D) 24
E) none of these

Question 45

Which of the following compounds displays two triplets and a singlet in its ¹H NMR spectrum?

A) CH₃CH(OCH₃)₂
B) CH₃OCH₂CH₂OCH₃
C) CH₃OCH₂CH(OH)CH₃
D) CH₃OCH₂CH₂CH₂CH₂OCH₃
E) none of these

Question 46

Determine the multiplicity of each signal in the expected ¹H NMR spectrum of the following compound.

Question 47

Determine the multiplicity of each signal in the expected ¹H NMR spectrum of the following compound.

Question 48

Which of the following compounds will display only three singlets in its ¹H NMR spectrum?

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

Question 49

Determine the multiplicity of each signal in the expected ¹H NMR spectrum of 2,3-dimethyl-2-pentanol.

Question 50

How many ¹H NMR signals does 2-chloro-3-methyl-2-butene exhibit?

A) 1
B) 2
C) 3
D) 4
E) none of these

Question 51

Determine the multiplicity of each signal in the expected ¹H NMR spectrum of the following compound.

Question 52

Presence of which of the following protons is confirmed by D₂O exchange?

A) OH
B) NH₂
C) CH
D) A & B
E) none of these

Question 53

Which of the following protons appear most upfield in the ¹H NMR spectrum?

A) I
B) II
C) III
D) IV
E) none of these

Question 54

Aromatic protons produce signal in the range of 7-8 ppm, due to the _________effect of $\pi$ electrons

A) diamagnetic anisotropy
B) paramagnetic anisotropy
C) diamagnetic isotropy
D) paramagnetic isotropy
E) none of these

Question 55

Which of the following is the maximum multiplicity observed for H_c protons in the following compound? Assume that J_cd and J_cb values are different.

A) 5
B) 6
C) 8
D) 12
E) none of these

Question 56

Which of the following compounds will display only two singlets in its ¹H NMR spectrum?

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

Question 57

Predict the chemical shifts for the signals in the ¹H NMR spectrum for the following compound.

Question 58

Determine the multiplicity of each signal in the expected ¹H NMR spectrum of the following compound.

Question 59

Which of the following compounds will display a singlet, a triplet and a quartet in its ¹H NMR spectrum?

A) 2-chloro-4-methylpentane
B) 3-chloro-2-methylpentane
C) 3-chloropentane
D) 1-chloro-2,2-dimethylbutane
E) 3-chloro-3-methylpentane

Question 60

Which of the following compounds gives a ¹H NMR spectrum consisting of only a singlet?

A) 1,1-dichloropropane
B) 1,3-dichloropropane
C) 1,2-dichloropropane
D) 2,2-dichloropropane
E) none of these

Question 61

Determine the multiplicity and predict the chemical shifts of each signal in the expected ¹H NMR spectrum of the following compound.

Question 62

The ¹H NMR spectrum of ethaneamine(CH₃CH₂NH₂) displays a singlet for the NH₂ protons instead of a triplet. Explain why.

Question 63

How would you use ¹H NMR spectroscopy to distinguish between the following compounds?

Question 64

How would you use ¹H NMR spectroscopy to distinguish between the following compounds?

A) I=3 & II=2 signals
B) I=4 & II=3 signals
C) I=5 & II=3 signals
D) none of these

Question 65

How many signals would you expect to find in the ¹³C NMR spectrum of the following compound?

A) 6
B) 7
C) 8
D) 9
E) none of these

Question 66

How many signals would you expect to find in the ¹³C NMR spectrum of the following compound?

A) 6
B) 7
C) 8
D) 9
E) none of these

Question 67

Propose a structure for a compound with molecular formula C₈H₁₄O₃ that fits the following spectroscopic data.
IR:1820cm^-1, 1760cm^-1
1H NMR: 1.0 $\delta$ (triplet, I=6), 1.6 $\delta$ (sextet, I=4), 2.2 $\delta$ (triplet, I=4)

Question 68

The broadband decoupling in ¹³CNMR suppresses ________ splitting.

A) .¹²C-¹³C
B) .¹²C-¹H
C). ¹³C-¹³C
D). ¹³C-¹H
E) none of these

Question 69

The off-resonance decoupling in ¹³CNMR allows for ________ splitting.

A). ¹²C-¹³C
B) .¹²C-¹H
C) .¹³C-¹³C
D). ¹³C-¹H
E) none of these

Question 70

Propose a structure for a compound with molecular formula C₁₀H₁₂O that fits the following spectroscopic data.
IR:1680cm^-1
1H NMR: 1.0 $\delta$ (triplet, I=3), 1.5 $\delta$ (sextet, I=2), 2.6 $\delta$ (triplet, I=2), 7.4 $\delta$ (triplet, I=2), 7.5 $\delta$ (triplet, I=1), 7.9 $\delta$ (doublet, I=2)

Question 71

How many signals would you expect to find in the ¹³C NMR spectrum of the following compound?

A) 2
B) 3
C) 4
D) 5
E) none of these

Question 72

Propose a structure for a compound with molecular formula C₅H₁₁Cl, that fits the following spectroscopic data:
¹H NMR: 0.9 $\delta$ (triplet, I=3), 1.3 $\delta$ (sextet, I=2), 1.5 $\delta$ (quartet, I=2), 1.6 $\delta$ (doublet, I=3), 3.6 $\delta$ (sextet, I=1)

Question 73

How would you use ¹H NMR spectroscopy to distinguish between the following compounds?

Question 74

Determine the multiplicity and predict the chemical shifts of each signal in the expected ¹H NMR spectrum of the following compound.

Question 75

Determine the multiplicity and predict the chemical shifts of each signal in the expected ¹H NMR spectrum of the following compound.

Question 76

A compound with a molecular formula C₉H₁₂ has the following ¹H NMR spectrum. Which of the following structures is consistent with this spectrum?

A) I
B) II
C) III
D) IV
E) none of these

Question 77

The ¹H NMR spectrum of alcohols displays a singlet for OH protons in the range of
2-5ppm. Explain how you will confirm the signal for OH protons..

Question 78

How many signals would you expect to find in the ¹³C NMR spectrum of the following compounds?

A) I-5, II-8
B) I-3, II-6
C) I-4, II-8
D) I-5, II-6
E) none of these

Question 79

The ¹H NMR spectrum of 1-propanol displays a singlet for the OH proton instead of a triplet. Explain why.

Question 80

How would you use ¹H NMR spectroscopy to distinguish between the following compounds?