Deck 15: Infrared Spectroscopy and Mass Spectrometry

Question 1

Which of the following electromagnetic radiation has the longest wavelength?

A) UV
B) X-ray
C) IR
D) microwave
E) visible

Answer 1

microwave

Question 2

Rank absorption of the indicated bonds in decreasing (highest to lowest) order of wavenumber.

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

Answer 2

I>II>III

Question 3

Which of the following vibrations are observed in IR spectroscopy?

A) stetching
B) rotational
C) bending
D) A & B
E) A & C

Answer 3

A & C

Question 4

Which of the following is currently most often used to indicate the location of a signal on an IR spectrum?

A) wavelength
B) wavenumber
C) frequency
D) A & B
E) all of these

Question 5

Which of the following are units for wavenumber in IR spectroscopy?

A) cm^-1
B) cm
C) J.s^-1
D) mm
E) none of these

Question 6

Rank absorption of the indicated bonds in decreasing (highest to lowest) order of wavenumber.

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

Question 7

Absorption of _______radiation results in vibrational excitation of the bonds in a compound.

A) UV
B) Microwave
C) IR
D) Visible
E) x-ray

Question 8

Which of the following statement(s) is(are) true about the frequency of a stretching vibration according to Hooke's law?

A) it is directly proportional to strength of the bond & the reduced mass
B) it is inversely proportional to strength of the bond & the reduced mass
C) it is directly proportional to strength of the bond
D) it is inversely proportional to the reduced mass
E) C & D

Question 9

Which of the following information is primarily obtained from infrared spectroscopy?

A) arrangement of carbon and hydrogen atoms in a compound
B) molecular weight of a compound
C) conjugated $\pi$ system present in a compound
D) functional groups present in a compound
E) all of these

Question 10

Which of the following electromagnetic radiation has the highest energy?

A) UV
B) X-ray
C) IR
D) microwave
E) visible

Question 11

Which one of the following compounds will have the lowest wavenumber for carbonyl absorption?

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

Question 12

Which of the following wavenumber corresponds to the fingerprint region on an IR spectrum?

A) 1500-4000cm^-1
B) 400-4000cm^-1
C) 400-1500cm^-1
D) 1500-2500cm^-1
E) none of these

Question 13

Which of the following is not true about electromagnetic radiation?

A) frequency is directly proportional to wavelength
B) frequency is directly proportional to energy
C) frequency is inversely proportional to wavelength
D) wavelength is inversely proportional to energy
E) none of these

Question 14

Which of the following wavenumber corresponds to the functional group region on an IR spectrum?

A) 1500-4000cm^-1
B) 400-4000cm^-1
C) 400-1500cm^-1
D) 1500-2500cm^-1
E) none of these

Question 15

Which of the following electromagnetic radiation has the highest frequency?

A) UV
B) X-ray
C) IR
D) microwave
E) visible

Question 16

Which one of the following compounds will have the highest wavenumber for C=C absorption?

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

Question 17

Arrange the following electromagnetic radiation in decreasing (highest to lowest) order of wavelength.

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

Question 18

Which one of the following compounds will have the lowest wavenumber for carbonyl absorption?

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

Question 19

Arrange the following electromagnetic radiation in decreasing (highest to lowest) order of frequency.

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

Question 20

Rank absorption of the indicated bonds in decreasing (highest to lowest) order of wavenumber.

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

Question 21

For the following pair of compounds the expected stretching absorption of the C=O bond is 1685cm^-1 & 1655cm^-1 respectively. Explain using both words and structural drawings.

Question 22

Carboxylic acids show a very broad absorption for the OH compared to alcohols, because they can form a ______.

A) dimer
B) polymer
C) trimer
D) tetramer

Question 23

Concentrated alcohols show a _____absorption in the region of 3200-3600cm^-1, due to _____.

A) sharp, hydrogen bonding
B) broad, hydrogen bonding
C) sharp, polarity
D) broad, polarity

Question 24

Diluted alcohols show a _____absorption around 3600cm^-1, due to _____.

A) sharp, hydrogen bonding
B) broad, hydrogen bonding
C) sharp, absence of hydrogen bonding
D) broad, absence of hydrogen bonding

Question 25

For each of the following IR spectra determine if it is consistent with the structure of an alcohol, a ketone, an aldehyde, a carboxylic acid, a primary amine or a secondary amine.
I. SDBS: National Institute of Advanced Industrial Science and Technology
II.

Question 26

Which of the following alkene groups will produce the stronger signal? Explain why.

Question 27

How can you distinguish between cyclohexanol and cyclohexanecarboxylic acid using IR spectroscopy?

Question 28

Which of the following bonds has the strongest absorption?

A) C=N
B) C $\equiv$ C
C) C=O
D) sp²C-H
E) C-O

Question 29

Which of the following statement(s) is(are) true for an IR-active bond?

A) the bond must be symmetrical
B) a vibration must result in a change of bond length
C) a vibration must result in a change of bond angle
D) a vibration must result in a change of bond dipole
E) all of these

Question 30

The C-O absorption in carboxylic acids appears around 1250cm^-1, where as the C-O absortion in alcohol appears around 1050cm^-1. Explain why.

Question 31

Which of the following compounds will have the highest wavenumber for carbonyl absorption?

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

Question 32

Primary amines show two medium absorption bands around 3400 cm^-1, due to _______.

A) symmetric stretching
B) asymmetric stretching
C) both symmetric and asymmetric stretching
D) hydrogen bonding

Question 33

For each of the following IR spectra determine if it is consistent with the structure of an alcohol, a ketone, an aldehyde, a carboxylic acid, a primary amine or a secondary amine.
I. SDBS: National Institute of Advanced Industrial Science and Technology
II. SDBS: National Institute of Advanced Industrial Science and Technology

Question 34

Which of the following compounds will show a broad absorption around 3300 cm^-1 and a sharp absorption at 1650 cm^-1?

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

Question 35

Which of the following bonds has the weakest absorption?

A) C=C
B) O-H
C) C=O
D) sp³C-H
E) A & D

Question 36

Which of the following alkene groups will produce the stronger signal? Explain why.

Question 37

For the following pair of compounds the expected stretching absorption of the C=O bond is 1685cm^-1 & 1715cm^-1 respectively. Explain using both words and structural drawings.

Question 38

Which of the following alkene groups will produce the strongest signal?

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

Question 39

Which of the following bonds is IR-inactive?

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

Question 40

Rank absorption of the indicated bonds in decreasing (highest to lowest) order of wavenumber.

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

Question 41

A compound with molecular formula C₆H₁₀O, shows absorptions at 1720 cm^-1 and at 2980 cm^-1 on the IR spectrum. Propose a possible structure for this compound.

Question 42

Which of the following compounds will show two absorptions at 2700 cm^-1 and at 2800 cm^-1 along with the carbonyl absorption?

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

Question 43

Which one of the following compounds is consistent with the following IR spectrum? SDBS: National Institute of Advanced Industrial Science and Technology

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

Question 44

Which of the following compounds will have the lowest wavenumber for carbonyl absorption?

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

Question 45

A compound with molecular formula C₄H₈O₂, shows absorptions at 2200-3600 cm^-1 (broad), 1720 cm^-1 and at 1200 cm^-1 on the IR spectrum. Propose a possible structure for this compound.

Question 46

Which one of the following compounds is consistent with the following IR spectrum? SDBS: National Institute of Advanced Industrial Science and Technology

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

Question 47

For the following reaction, which of the following change(s) in the IR spectrum is consistent with conversion of the reactant to the product?

A) absorption at 2150 cm^-1 should disappear
B) absorption at 3300 cm^-1 and 2150cm^-1 should disappear
C) absorption at 2250 cm^-1 should disappear, a new absorption at 3300 cm^-1 should appear
D) absorption at 1650 cm^-1 should disappear, a new absorption at 3300 cm^-1 should appear
E) absorption at 3300 cm^-1 and 2150cm^-1 should disappear, a new absorption at 1720 cm^-1 should appear

Question 48

Which one of the following compounds is consistent with the following IR spectrum? SDBS: National Institute of Advanced Industrial Science and Technology

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

Question 49

Which one of the following compounds is consistent with the following IR spectrum? SDBS: National Institute of Advanced Industrial Science and Technology

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

Question 50

Which of the following compounds will have two absorptions at 1820 cm^-1 and 1740cm^-1?

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

Question 51

Which one of the following compounds is consistent with the following IR spectrum? SDBS: National Institute of Advanced Industrial Science and Technology

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

Question 52

Which of the following compounds will have the highest wavenumber for carbonyl absorption?

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

Question 53

Which one of the following compounds is consistent with the following IR spectrum? SDBS: National Institute of Advanced Industrial Science and Technology

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

Question 54

Which one of the following compounds is consistent with the following IR spectrum? SDBS: National Institute of Advanced Industrial Science and Technology

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

Question 55

Which of the following compounds will show two sharp absorption at 3300 cm^-1 and at 2150 cm^-1?

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

Question 56

Which of the following compounds will show an absorption at 2250 cm^-1?

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

Question 57

Which of the following compounds will show absorptions at 1640 cm^-1, 2950 cm^-1 and 3050 cm^-1 on the IR spectrum?

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

Question 58

For the following reaction, which of the following change(s) in the IR spectrum is consistent with conversion of the reactant to the product?

A) absorption at 2250 cm^-1 should disappear
B) absorption at 3200-3400 cm^-1 and 1720cm^-1 should appear
C) absorption at 2250 cm^-1 should disappear, new absorptions at 2600-2800 cm^-1 and 1720 cm^-1 should appear.
D) absorption at 2250 cm^-1 should disappear, a new absorption around 3400 cm^-1 should appear.
E) none of these

Question 59

Which of the following is true about the IR spectrum of the compound shown below?

A) absorptions at 1720 cm^-1 & 2150 cm^-1
B) absorptions at 1800 cm^-1 & 2150 cm^-1
C) absorptions at 1720 cm^-1 & 2250 cm^-1
D) absorptions at 1800 cm^-1 & 2250 cm^-1
E) absorptions at 1650 cm^-1 & 2150 cm^-1

Question 60

A compound with molecular formula C₃H₉N, shows absorptions at 3400 cm^-1 (two), 2980 cm^-1 and at 1100 cm^-1 on the IR spectrum. Propose a possible structure for this compound.

Question 61

Which of the m/z values corresponds to the base peak in the following mass spectrum?

A) 45
B) 44
C) 29
D) 15
E) none of these

Question 62

Which of the following is true about CH₃CH₃^{+ .} ?

A) it is the parent ion of ethane
B) it is a molecular ion of ethane with m/z =30
C) it is a fragment of propane
D) A & B
E) none of these

Question 63

Which of the m/z values correspond to the molecular ion for the following compound?

A) 18
B) 82
C) 100
D) 102
E) 103

Question 64

Which of the following compounds will have odd m/z value for the molecular ion?

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

Question 65

Predict the product for the following reaction and explain how you will use IR spectroscopy to monitor the progress of the reaction.

Question 66

In mass spectrometry, the cations are separated by their ______________.

Question 67

For the following reaction, which of the following change(s) in the IR spectrum is consistent with conversion of the reactant to the product?

A) absorption at 3200-3600 cm^-1 should disappear
B) absorption at 3200-3600 cm^-1 and 1100 cm^-1 should disappear
C) absorption at 1100 cm^-1 should disappear, a new absorption at 3100 cm^-1 should appear
D) absorption at 1650 cm^-1 should disappear, a new absorption at 3300 cm^-1 should appear.
E) none of these

Question 68

In mass spectrometry using electron impact ionization technique, a beam of high-energy electrons initially ejects one electron from the compound being studied. This produces a positively charged ion called the ____________________.

Question 69

Which of the following is always true about the base peak in a mass spectrum?

A) peak corresponding to molecular ion
B) peak corresponding to the most abundant ion
C) peak corresponding to lowest m/z
D) A & C
E) none of these

Question 70

For the following reaction, which of the following change(s) in the IR spectrum is consistent with conversion of the reactant to the product?

A) absorption at 3300-3400 cm^-1 should disappear
B) absorption at 3300-3400 cm^-1 and 1100 cm^-1 should disappear
C) absorption at 1100 cm^-1 should disappear, a new absorption at 3100 cm^-1 should appear
D) absorption at 1650 cm^-1 should disappear, a new absorption at 3300 cm^-1 should appear.
E) none of these

Question 71

Mass spectrometry is primarily used to determine:

A) molecular formula of a compound
B) molecular weight of a compound
C) conjugation in a compound
D) A & B
E) A & C

Question 72

Which of the following is not true about the molecular ion in mass spectrometry?

A) The molecular ion is produced by loss of one electron from the molecule.
B) The mass of the molecular ion is equivalent to the mass of the molecule.
C) The ion is produced by a loss of pair of electrons from the molecule.
D) The molecular ion is often unstable and can undergo fragmentation.
E) none of these

Question 73

Which of the m/z values correspond to the molecular ion peak in the following mass spectrum?

A) 45
B) 44
C) 29
D) 15
E) none of these

Question 74

In mass spectrometry, the tallest peak is assigned an intensity of 100% and is referred to as the ______________.

Question 75

The separation of ions in the mass spectrometer is done by their ______.

A) electrons to protons ratio
B) mass to neutrons ratio
C) protons to neutrons ratio
D) mass to charge ratio
E) none of these

Question 76

For the following reaction, explain how you will use IR spectroscopy to monitor the progress of the reaction.

Question 77

Which of the following is initially produced when a compound is bombarded with high energy electrons?

A) anion
B) free radical
C) radical cation
D) cation
E) none of these

Question 78

Predict the product for the following reaction and explain how you will use IR spectroscopy to monitor the progress of the reaction.

Question 79

Which of the following m/z values corresponds to the base peak for 2-chloro-2-methylpropane?

A) 15
B) 92
C) 77
D) 47
E) 57

Question 80

Predict the product for the following reaction and explain how you will use IR spectroscopy to monitor the progress of the reaction.