Deck 13: Structure Determination I

Question 1

What is the degree of unsaturation of a molecule with the molecular formula C₉H₁₃ClO₃?

A)1
B)3
C)5
D)7

Answer 1

3

Question 2

How many unique ¹³C NMR signals are present in the following molecule?

A)2
B)3
C)4
D)6

Answer 2

4

Question 3

What is the multiplicity of the indicated hydrogen?

A)singlet
B)doublet
C)triplet
D)quartet

Answer 3

doublet

Question 4

Which of the following best describes a ¹³C-DEPT-45 spectrum?

A)Primary and tertiary carbons appear as positive signals.
B)Primary and tertiary carbons appear as negative signals.
C)Primary carbons appear as positive signals,and tertiary carbons appear as negative signals.
D)Primary carbons appear as negative signals,and tertiary carbons appear as positive signals.

Question 5

Which proton would you expect to be the most downfield in the following molecule?

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

Question 6

How many unique ¹H NMR signals are present in the following molecule?

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

Question 7

Which of the following best describes the aromatic molecule represented by the ¹H NMR shown below?

A)monosubstituted
B)o-disubstituted
C)m-disubstituted
D)p-disubstituted

Question 8

Which of the following best describes the aromatic molecule represented by the ¹H NMR shown below?

A)monosubstituted
B)o-disubstituted
C)m-disubstituted
D)p-disubstituted

Question 9

How many unique ¹H NMR signals are present in the following molecule?

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

Question 10

What is the expected multiplicity of the indicated proton?

A)singlet
B)doublet
C)triplet
D)quartet

Question 11

What is the degree of unsaturation of a molecule with the molecular formula C₈H₁₃N?

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

Question 12

How many unique ¹H NMR signals are present in the following molecule?

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

Question 13

What is the atomic effect of applying a magnetic field to a molecule?

A)Nuclei spin parallel to the magnetic field.
B)Nuclei spin antiparallel to the magnetic field.
C)Nuclei spin both parallel and antiparallel to the magnetic field.
D)Nuclei spin in random directions.

Question 14

Which of the following best describes a ¹³C-DEPT-135 spectrum?

A)Secondary and tertiary carbons appear as positive signals.
B)Secondary and tertiary carbons appear as negative signals.
C)Secondary carbons appear as positive signals and tertiary carbons appear as negative signals.
D)Secondary carbons appear as negative signals and tertiary carbons appear as positive signals.

Question 15

What is the effect of introducing energy to molecules in a magnetic field?

A)Nuclei transition from parallel spin to antiparallel spin relative to the magnetic field.
B)Nuclei transition from antiparallel spin to parallel spin relative to the magnetic field.
C)Electrons transition from parallel spin to antiparallel spin relative to the magnetic field.
D)Electrons transition from antiparallel spin to parallel spin relative to the magnetic field.

Question 16

How many unique ¹³C NMR signals are present in the following molecule?

A)2
B)3
C)4
D)6

Question 17

What form of carbon can be detected in a ¹³C-DEPT-90 spectrum?

A)primary
B)secondary
C)tertiary
D)quaternary

Question 18

How many unique ¹H NMR signals are present in the following molecule?

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

Question 19

Which of the following best describes protons placed near electron withdrawing groups?

A)They are shielded and upfield.
B)They are shielded and downfield.
C)They are deshielded and upfield.
D)They are deshielded and downfield.

Question 20

Which of the following nuclei is NOT NMR active?

A)(¹H)
B)(¹²C)
C)(¹⁴N)
D)(¹⁷O)

Question 21

How many unique proton signals would be expected in a ¹H NMR spectrum run in D₂O?

A)3
B)4
C)5
D)6

Question 22

What represents the integration ratio of peaks in the ¹H NMR spectrum for the molecule shown below?

A)3:2:2:3
B)3:1
C)6:2:2
D)3:3:1:1:1:1

Question 23

A ¹³C-DEPT-90 spectrum produces positive signals for secondary carbons.

Question 24

How many neighbouring protons does a proton with a doublet multiplicity have in a ¹H NMR?

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

Question 25

What is the multiplicity of the indicated hydrogen?

A)singlet
B)doublet
C)triplet
D)quartet

Question 26

A ¹³C-DEPT-90 spectrum produces positive signals for primary carbons.

Question 27

Which carbon would you expect to be furthest downfield on a ¹³C NMR spectrum?

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

Question 28

How many neighbouring protons does a proton with a triplet multiplicity have in an ¹H NMR?

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

Question 29

What information is obtained by the multiplicity of a proton peak in a ¹H NMR spectrum?

A)the number of hydrogen types
B)the relative number of hydrogens of each type
C)the chemical environment around a hydrogen
D)the molecular connectivity near the hydrogen atom

Question 30

How many positive signals would be expected in a ¹³C-DEPT-135 of the following molecule?

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

Question 31

How many positive signals would be expected in a ¹³C-DEPT-135 of the following molecule?

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

Question 32

What type of electromagnetic radiation is required to flip the spin of nuclei in an NMR scan?

A)X-rays
B)UV-Vis
C)microwaves
D)radiowaves

Question 33

A ¹³C-DEPT-135 spectrum produces negative signals for secondary carbons.

Question 34

How many degrees of unsaturation does phenol contain?

A)3
B)4
C)5
D)6

Question 35

What represents the integration ratio of peaks in the ¹H NMR spectrum for the molecule shown below?

A)9:2:2:9
B)9:2
C)9:1:1
D)3:3:3:2

Question 36

What is the multiplicity of the indicated hydrogen?

A)singlet
B)doublet
C)triplet
D)quartet

Question 37

Which of the following can introduce unsaturation into a molecular formula?

A)rings
B)ð bonds
C)both rings and ð bonds
D)ó bonds

Question 38

Which of the following molecules would have the most downfield signal in a ¹H NMR?

A)CH₄
B)CHCl₃
C)CHBr₃
D)CHF₃

Question 39

What molecule is used as a reference for NMR spectroscopy?

A)trimethylsilane
B)tetramethylsilane
C)trimethylsilane chloride
D)trimethylsilane oxide

Question 40

How many positive signals would be expected in a ¹³C-DEPT-135 of the following molecule?

A)2
B)3
C)5
D)8

Question 41

A ¹³C-DEPT-45 spectrum produces positive signals for tertiary carbons.

Question 42

A doublet in a ¹H NMR spectrum represents a proton with a single proton neighbour.

Question 43

Electromagnetic radiation in the UV-Vis range is required in NMR spectroscopy.

Question 44

Stronger NMR magnets increase the energy difference between the á and â spin states of a nuclei.

Question 45

The aromatic protons on a para-substituted aromatic ring are seen as doublets on a ¹H NMR spectrum.

Question 46

A quartet in a ¹H NMR spectrum represents a proton with four proton neighbours.

Question 47

¹²C is a NMR active nuclei.

Question 48

C₁₄H₁₆N₂ has eight degrees of unsaturation.

Question 49

p-dichlorobenzene contains a single peak in a ¹H NMR spectrum.

Question 50

C₆H₁₂O₆ has two degrees of unsaturation.

Question 51

p-dichlorobenzene has three degrees of unsaturation.

Question 52

Quaternary carbons don't show any signals in any ¹³C-DEPT scan.

Question 53

An NMR spectrum is a result of nuclei excitation.

Question 54

Protons in electron-rich environments are found upfield in ¹H NMR spectra.

Question 55

Anisotropy is a result of magnetic fields created by electron currents.

Question 56

Hydrogen bonding shields protons in ¹H NMR spectra.

Question 57

Nuclei in close proximity above the plane of an aromatic ring are shielded by anisotropy.

Question 58

The multiplicity of a peak in a ¹H NMR spectrum tells the molecular connectivity of a proton within a molecule.

Question 59

Integration of a peak in a ¹H NMR spectrum tells the absolute number of protons within a chemical environment.

Question 60

Acidic protons are masked in ¹H NMR spectra when run in D₂O.

Question 61

A triplet in a ¹H NMR spectrum represents a proton with _______________ neighbours.

Question 62

Predict the structure of a molecule with the formula C₆H₁₅N from the ¹H NMR shown below and assign each peak.

Question 63

A primary carbon is a(n)_______________ signal in a ¹³C DEPT-45 spectrum.

Question 64

C₁₁H₁₅NO has _______________ degrees of unsaturation.

Question 65

Protons near electron withdrawing group are found _______________ on a ¹H NMR spectrum.

Question 66

Predict the structure of a molecule with the formula C₈H₅Cl from the ¹H NMR shown below and assign each peak.

Question 67

Predict the structure of a molecule with the formula C₁₁H₁₅NO from the ¹H NMR and ¹³C NMR shown below.

Question 68

Determine the types of signals of the carbons in a ¹³C DEPT 45 and ¹³C DEPT 135 spectrum of the following molecule.

Question 69

Integrations of peaks in ¹H NMR spectra represent a relative number of protons.

Question 70

A(n)_______________ in a ¹H NMR spectrum represents a proton with four neighbours

Question 71

_______________ carbons are always absent in ¹³C DEPT spectrums.

Question 72

Predict the structure of a molecule with the formula C₈H₉Cl from the ¹H NMR shown below and assign each peak.

Question 73

_______________ spectra can produce negative signals for secondary carbons.

Question 74

Determine the expected multiplicity of the protons indicated at each point of the molecule shown below.

Question 75

Protons found near electron withdrawing groups in ¹H NMR spectra are considered _______________ .

Question 76

Diastereotopic protons are equivalent.

Question 77

C₁₄H₁₆N₂ has _______________ degrees of unsaturation.

Question 78

A negative signal in a ¹³C DEPT-135 spectrum represents a(n)_______________ carbon

Question 79

Predict the structure of a molecule with the formula C₈H₆ from the ¹H NMR shown below and assign each peak.