Deck 11: Infrared and Nuclear Magnetic Resonance Spectroscopy

Question 1

How many principal vibrations does benzene (C₆H₆) have?

A) 30
B) 29
C) 18
D) 17

Answer 1

30

Question 2

Very prominent peaks in the IR spectrum are sufficient to distinguish between which compounds?
I. butanoic acid and methyl butanoate
II. dimethylamine and N,N-dimethylformamide
III. triethylamine and dimethylpropanamine
IV. 2-pentanol and 3-pentanol

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

Answer 2

I, II

Question 3

Which is the approximate energy range for absorptions in the infrared region of the electromagnetic spectrum?

A) 0.042 to 0.42 kJ/mol
B) 0.042 to 0.42 kW/mol
C) 420 to 2,100 kJ/mol
D) 8.4 to 41.9 kJ/mol

Answer 3

8.4 to 41.9 kJ/mol

Question 4

How many principal vibrations does aspartame have?

A) 99
B) 141
C) 112
D) 111

Question 5

Which is the order of increasing bond stretching frequency (lowest first)?
I. C=N
II. C=O
III. C=C
IV. C=S

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

Question 6

Which region in the IR spectrum could be used to distinguish between naproxen and diphenhydramine (Benadryl)?

A) 3000-3050 cm^-1
B) 1360-1380 cm^-1
C) 3100-3500 cm^-1
D) 2400-3500 cm^-1

Question 7

A compound has the molecular formula C₅H₁₀O, and strong absorptions at 1100 and 3350 cm^-1. Which is the most likely structure for the compound?

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

Question 8

Which is the wavelength ( $\mu$ m) of an infrared absorption band at 500 cm^-1?

A) 0.2
B) 2.0
C) 20
D) 25

Question 9

The broadening of the stretching vibration peak for alcohols in the liquid or solid phase is mainly due to which of the following?

A) water contamination
B) a strong dipole moment
C) hydrogen bonding
D) coupling peaks

Question 10

Which is the index of hydrogen deficiency for a compound having molecular formula C₇H₅Cl₂NO?

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

Question 11

Which is the approximate energy range for absorptions in the infrared region of the electromagnetic spectrum?

A) 50 to 100 kcal/mol
B) 10 to 50 kcal/mol
C) 2 to 10 kcal/mol
D) 0.01 to 0.1 kcal/mol

Question 12

Prominent peaks in the IR spectrum are sufficient to distinguish between which compounds?
I. diethyl ether and diethylamine
II. cyclohexanone and cyclopentanone
III. pentanal and pentanol
IV. 2-hexene and 3-hexene

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

Question 13

Which is the wave number for an infrared band at 5 microns ( $\mu$ m)?

A) 500 cm^-1
B) 2000 cm^-1
C) 5000 cm^-1
D) 10,000 cm^-1

Question 14

The stretching vibration peak for alcohols is very sharp when the spectrum is recorded in the gas phase. This is mainly due to the following:

A) lower concentration
B) absence of hydrogen bonding
C) higher degree of hydrogen bonding
D) higher temperature

Question 15

Which compounds will have a particularly weak characteristic IR stretching frequency?

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

Question 16

How many principal vibrations does anthracene have?

A) 36
B) 37
C) 66
D) 67

Question 17

Which is the index of hydrogen deficiency for a compound having molecular formula C₁₂H₁₃Br₂NO₂?

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

Question 18

Which region in the IR spectrum could be used to distinguish between the neurotransmitters acetylcholine and 4-aminobutanoic acid ?

A) 2900-3000 cm^-1
B) 1360-1380 cm^-1
C) 3100-3500 cm^-1
D) 2400-3500 cm^-1

Question 19

Which is the order of increasing bond stretching frequency (lowest first)?
I. C-H
II. N-H
III. O-H
IV. F-H

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

Question 20

What is the general formula for the calculation of the number of principal vibrations of a molecule that extends in all three directions (e.g. cyclohexane)? N is the number of atoms that form the molecule.

A) 3N
B) 3N-6
C) 3N-3
D) 3N-5

Question 21

Prominent peaks in the IR spectrum are sufficient to distinguish between which compounds?
I. butane and cyclobutane
II. toluene and methylcyclohexane
III. 2-pentanone and 3-pentanone
IV. pentanal and 1-pentene

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

Question 22

How many states in a static magnetic field can be discerned for an NMR-active isotope with a spin of 1 (e.g. ²D)?

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

Question 23

Which compound has characteristic IR peaks at 3100 cm^-1 and 1650 cm^-1, but not 1480 cm^-1?

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

Question 24

Which compound has a sharp IR absorption at 1710 cm^-1 and a very broad band at 3300 cm^-1?

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

Question 25

How many sets of equivalent hydrogen atoms are there for 2-propanol?

A) 2
B) 3
C) 4
D) 8

Question 26

Which compound has characteristic IR peaks at 3100 cm^-1, 1600 cm^-1, and 1475 cm^-1?

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

Question 27

Which region in the IR spectrum could be used to distinguish between aspirin and acetaminophen (tylenol)?

A) 3000-3050 cm^-1
B) 1360-1380 cm^-1
C) 3100-3500 cm^-1
D) 2400-3500 cm^-1

Question 28

Which regions in the IR spectrum could be used to distinguish between benzene and cyclohexane?

A) 1360-1380 cm^-1
B) 2900-3100 cm^-1
C) 1680-1750 cm^-1
D) 3200-3600 cm^-1

Question 29

A compound has a molecular formula of C₅H₉N and the IR spectrum has peaks in the region of 2900 to 3000 cm^-1, 1450 cm^-1 and 1375 cm^-1, but no peaks in the region of 3000-3500 cm^-1. Which of the following could be the compound?

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

Question 30

Which compound has a characteristic IR peak at 2900 cm^-1?

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

Question 31

How many states in a static magnetic field can be discerned for an NMR-active isotope with a spin of 1/2 (e.g. ¹H, ¹³C)?

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

Question 32

The chemical shift in NMR spectroscopy is observed, because________________________.

A) the magnetic field is not constant during the measurement
B) of the interfering magnetic field caused by the electrons in the molecule
C) many elements have more than one isotope
D) the interference of neighboring nuclei

Question 33

Which region in the IR spectrum could be used to distinguish between benzyl amine and benzamide?

A) 1475 cm^-1 and 1600 cm^-1
B) 3030 cm^-1
C) 3100-3500 cm^-1
D) 1630-1690 cm^-1

Question 34

Which region in the IR spectrum could be used to distinguish between aspirin and naproxen (aleve)?

A) 2900-3000 cm^-1
B) 1360-1380 cm^-1
C) 1700-1800 cm^-1
D) 3100-3500 cm^-1

Question 35

Which regions in the IR spectrum could be used to distinguish between butanoic acid and 2-butanone?

A) 3200-3600 cm^-1
B) 1600 cm^-1
C) 1750-1800 cm^-1
D) 2500-3300 cm^-1

Question 36

Which compound has an IR absorption at 3300 cm^-1 but no band at 1710 cm^-1?

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

Question 37

How many states in a static magnetic field can be discerned for an NMR-active isotope with a spin of 3 (e.g. ¹⁰B)?

A) 6
B) 7
C) 8
D) 9

Question 38

Which region in the IR spectrum could be used to distinguish between aspartame and saccharine?

A) 3000-3050 cm^-1
B) 1060-1100 cm^-1
C) 1440-1465 cm^-1
D) 2900-3000 cm^-1

Question 39

A compound has a molecular formula C₇H₁₄O₂ and a broad signal in the region of 2850-3000 cm^-1 and a signal in the region of 1710-1780 cm^-1 in the IR spectrum. Which could be the compound?(Hint: There’s no broad absorption band near 3300 cm-1 in this spectrum..)

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

Question 40

Which is the most likely structure for a compound with molecular formula C₅H₈O, and an IR spectrum with an intense peak at 1710 cm^-1 but no peaks between 3000 and 3050 cm^-1?

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

Question 41

Which splitting pattern (H_a:H_b:H_c) is observed ?

A) singlet:doublet:singlet
B) singlet:triplet:doublet
C) singlet:triplet:singlet
D) doublet:sixtet:doublet

Question 42

Which compound has a singlet in the ¹H-NMR at approximately 2.0 ppm that integrates to 3 hydrogens?

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

Question 43

How many sets of equivalent hydrogen (H) and carbon (C) atoms are there for the following compound?

A) 6H, 9C
B) 12H, 17C
C) 6H, 17C
D) 8H, 9C

Question 44

Which are the relative areas of integration in the ¹H-NMR spectrum for 2-chloro-3-methylbutane?

A) 9:1:1
B) 3:3:3:1:1
C) 6:3:2
D) 6:3:1:1

Question 45

How many sets of equivalent carbon atoms are there for the following compound (C₁₆H₂₆O)?

A) 12
B) 14
C) 16
D) 13

Question 46

Which is the splitting pattern for the hydrogen atoms in 2,2-dibromopropane?

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

Question 47

Which is the splitting pattern for the indicated hydrogen atom?

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

Question 48

Which are the characteristic shift ranges for the indicated hydrogen atoms?

A) I = 0.8-1.0, II = 6.5-8.5, III = 2.2-2.5, IV = 2.1-2.3
B) I = 0.8-1.0, II = 2.2-2.5, III = 6.5-8.5, IV = 2.1-2.3
C) I = 2.2-2.5, II = 6.5-8.5, III = 0.8-1.0, IV = 2.1-2.3
D) I = 2.2-2.5, II = 6.5-8.5, III = 2.1-2.3, IV = 0.8-1.0

Question 49

Which is the order of increasing $\delta$ values in the ¹³C NMR spectra for the following carbon atoms?
CH₄ CH₃F CH₃Br CH₃OH CH₃Cl
I II III IV V

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

Question 50

Which compound has four sets of signals in the ¹H-NMR spectrum?

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

Question 51

Which are the relative areas of integration in the ¹H-NMR spectrum for the compound shown below?

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

Question 52

Which is the order in increasing chemical shift values in the ¹H-NMR spectrum for the indicated hydrogen atoms (farthest upfield first)?

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

Question 53

Which is the order of increasing $\delta$ values downfield from TMS for the methyl groups shown (farthest upfield first)?

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

Question 54

A compound gave two sets of signals in the ¹H-NMR spectrum with an integration ratio of 60 to 10. Which is the most likely structure for the compound?

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

Question 55

How many sets of equivalent hydrogen atoms are there for the following compound?

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

Question 56

The splitting pattern for a compound with molecular formula C₃H₅OCl gave a quartet and a triplet. Which is the most likely structure for this compound?

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

Question 57

How many sets of signals are there in the ¹H-NMR spectrum for diisopropyl ether?

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

Question 58

Sugar Cane is a so-called C4 plant, a plant having a different mechanism of carbon fixation (binding of atmospheric carbon) than other plants. Consequently, the ¹³C-content of C4 plants is enriched, relative to non-C4 plants. This biochemical finding can be used to detect the amount of sugar from sugarcane, which has been added to the grape juice before its fermentation, by measuring the ¹³C-isotope content in the resulting ethanol. How can you measure the ¹³C-content of ethanol in a wine-sample?

A) "chemical shift"
B) "integration of the signal using a sample with known ¹³C-content of ethanol as standard"
C) "¹H-¹H signal splitting"
D) "¹³C-¹³C signal splitting"

Question 59

Which compounds show signal splitting in the ¹H-NMR spectrum?

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

Question 60

How many sets of signals are there in the ¹H-NMR spectrum for 1,1-dichlorocyclohexane?

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

Question 61

The energy in kJ/mol of 3350 cm^-1 light is ___________________.

Question 62

How many sets of inequivalent carbon atoms are there for 1-bromo-3-chlorocyclohexane?

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

Question 63

A compound has three signals in the ¹³C NMR spectrum and two signals in the ¹H-NMR spectrum. Which is most likely the compound?

A) bromobenzene
B) para dibromobenzene
C) ortho dibromobenzene
D) meta dibromobenzene

Question 64

Testosterone is an anabolic steroid; estradiol is the predominant female sex hormone. How can you discern between these two hormones by using NMR spectroscopy? I) number of ¹³C-signals
II) number of ¹H-signals
III) chemical shifts
IV) ¹H-signal splitting

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

Question 65

The compounds shown below can be distinguished by which ¹H-NMR characteristics? I) number of signals
II) splitting
III) integration
IV) chemical shift

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

Question 66

Which statement is wrong?

A) H_a and H_b are doublets
B) H_c is a doublet
C) H_d is a doublet
D) H_e is a doublet

Question 67

Which compounds have 3 signals in the ¹³C NMR spectrum?

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

Question 68

Which statement is wrong?

A) H_a and H_b are doublets
B) H_c is a doublet
C) H_d is a triplet
D) H_e is a triplet

Question 69

A compound has two signals in the ¹³C NMR spectrum and a single signal in the ¹H-NMR spectrum. Which is most likely the compound?

A) dimethyl ether
B) diethyl ether
C) 2,2-dimethylpropane
D) methyl ethanoate

Question 70

The energy in kcal/mol of 606.06 $\mu$ m light is ___________________.

Question 71

How many sets of inequivalent carbon atoms are there for the following compound?

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

Question 72

The molecules shown below are enantiomers. How do they differ in their 1H-NMR spectra?

A) chemical shifts
B) signal splitting
C) integration
D) none of the above

Question 73

The energy in kcal/mol of 3350 cm^-1 light is ___________________.

Question 74

The compounds shown below can be distinguished by which ¹H-NMR characteristics? I) number of signals
II) splitting
III) integration
IV) chemical shift

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

Question 75

How many sets of equivalent hydrogen (H) and carbon (C) atoms are there for the following compound?

A) 5H, 9C
B) 11H, 17C
C) 5H, 17C
D) 7H, 9C

Question 76

The ___________________functional group has a characteristic absorption in the region of 1630-1800 cm^-1.

Question 77

A compound has a single signal in the ¹³C NMR spectrum and a single signal in the ¹H-NMR spectrum. Which is most likely the compound?

A) dimethyl ether
B) diethyl ether
C) 2,2-dimethylpropane
D) methyl ethanoate

Question 78

The compounds shown below can be distinguished by which ¹H-NMR characteristics? I) number of signals
II) splitting
III) integration
IV) chemical shift

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

Question 79

The ___________________functional group has a characteristic absorption in the region of 3200-3500 cm^-1.

Question 80

The molecules shown below are diastereomers. How do they differ in their 1H-NMR spectra?

A) chemical shifts
B) signal splitting
C) integration
D) none of the above