Question 1

Which compound would be expected to show intense IR absorption at 1640 cm-1?

Accepted Answer

A)  hex-1-ene 
B)  2-methylheptane 
C)  CH3CH2CH2OH 
D)  CH3CH2COCH3 
A)  hex-1-ene 
B)  2-methylheptane 
C)  CH3CH2CH2OH 
D)  CH3CH2COCH3

Question 2

Deduce a possible structure for the compound with the IR absorptions below.
C4H8O: 2950, 2820, 2715, 1715 cm-1

Accepted Answer

Question 3

Which has a lower characteristic stretching frequency, the C-H or C-D bond? Explain briefly.

Accepted Answer

C-D; heavi

Question 4

Which of the following molecules would be expected to have its C=C stretching frequency at the highest wavenumber: benzene, 1,3-pentadiene, or 1-pentene?

Accepted Answer

The answer of Which of the following molecules would be...

Question 5

What IR absorption is characteristic of the C-H stretch in alkanes?

Accepted Answer

A)  3500 cm-1 
B)  3300 cm-1 
C)  2950 cm-1 
D)  2250 cm-1 
E)  1710 cm-1 
A)  3500 cm-1 
B)  3300 cm-1 
C)  2950 cm-1 
D)  2250 cm-1 
E)  1710 cm-1

Question 6

Which of the following fragment peaks would not be present in the mass spectrum of n-hexane?

Accepted Answer

A)  87 
B)  71 
C)  57 
D)  43 
E)  29 
A)  87 
B)  71 
C)  57 
D)  43 
E)  29

Question 7

Which of the following structures is consistent with the mass spectrum shown below?

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Question 8

What spectroscopic technique can be used to determine the molecular formula of a compound?

Accepted Answer

high resol

Question 9

When a high energy electron impacts molecule M in the ionization chamber, what type of species is initially produced?

Accepted Answer

A)  cation 
B)  anion 
C)  radical 
D)  radical cation 
E)  radical anion 
A)  cation 
B)  anion 
C)  radical 
D)  radical cation 
E)  radical anion

Question 10

In what units are frequency values typically given?

Accepted Answer

Hertz or c

Question 11

In a mass spectrum, what m/z value would correspond to the following fragment?

Accepted Answer

The answer of In a mass spectrum, what m/z value...

Question 12

How does the O-H stretch in the IR spectrum of a carboxylic acid differ from the O-H stretch of an alcohol?

Accepted Answer

Because of the unusually strong hydrogen

Question 13

In an IR spectrometer, the ________ uses prisms or diffraction gratings to allow only one frequency of light to enter the detector at a time.

Accepted Answer

The answer of In an IR spectrometer, the ________ uses...

Question 14

Which IR band is typically more intense, the C≡C stretch or the C≡N stretch? Explain briefly.

Accepted Answer

The C≡N stretch tends to be mo

Question 15

Which of the following does not have a broad absorption with one or more spikes that is centered about 3300 cm-1 in the IR?

Accepted Answer

A)  (CH3CH2CH2)3N 
B)  (CH3CH2CH2)2NH 
C)  CH3CH2CH2NH2 
D)  (CH3)3CNH2 
E)  (CH2=CHCH2)2NH 
A)  (CH3CH2CH2)3N 
B)  (CH3CH2CH2)2NH 
C)  CH3CH2CH2NH2 
D)  (CH3)3CNH2 
E)  (CH2=CHCH2)2NH

Question 16

Provide an equation which relates the energy of a photon to its wavelength.

Accepted Answer

The answer of Provide an equation which relates the energy...

Question 17

Ethyne (HC   CH) does not show IR absorption in the region 2000-2500 cm-1 because ________.

Accepted Answer

A)  C-H stretches occur at lower energies 
B)  C   C stretches occur at about 1640 cm-1 
C)  there is no change in the dipole moment when the C   C bond in ethyne stretches 
D)  there is a change in the dipole moment when the C   C bond in ethyne stretches 
A)  C-H stretches occur at lower energies 
B)  C   C stretches occur at about 1640 cm-1 
C)  there is no change in the dipole moment when the C   C bond in ethyne stretches 
D)  there is a change in the dipole moment when the C   C bond in ethyne stretches

Question 18

Which of the following molecules has a characteristic stretch at 2250 cm-1?

Accepted Answer

A)  (CH3)2CHCH2OH 
B)  (CH3)3CH 
C)  (CH3)2CHCCN 
D)  (CH3)2CHCH=CH2 
E)  (CH3)2CHCO2CH3 
A)  (CH3)2CHCH2OH 
B)  (CH3)3CH 
C)  (CH3)2CHCCN 
D)  (CH3)2CHCH=CH2 
E)  (CH3)2CHCO2CH3

Question 19

How could IR spectroscopy be used to distinguish between the following pair of compounds?
CH2
    
CHCH2CH(CH3)2 and CH3CH2CH2CH(CH3)2

Accepted Answer

C @#IMG-DLM& C stretch around

Question 20

In order for a vibration mode to be observable in the IR, the vibration must change the ________ of the molecule.

Accepted Answer

The answer of In order for a vibration mode to...

Exam 12: Infrared Spectroscopy and Mass Spectrometry

Which compound would be expected to show intense IR absorption at 1640 cm-1?

Deduce a possible structure for the compound with the IR absorptions below. C4H8O: 2950, 2820, 2715, 1715 cm-1

Which has a lower characteristic stretching frequency, the C-H or C-D bond? Explain briefly.

Which of the following molecules would be expected to have its C=C stretching frequency at the highest wavenumber: benzene, 1,3-pentadiene, or 1-pentene?

What IR absorption is characteristic of the C-H stretch in alkanes?

Which of the following fragment peaks would not be present in the mass spectrum of n-hexane?

Which of the following structures is consistent with the mass spectrum shown below?

What spectroscopic technique can be used to determine the molecular formula of a compound?

When a high energy electron impacts molecule M in the ionization chamber, what type of species is initially produced?

In what units are frequency values typically given?

In a mass spectrum, what m/z value would correspond to the following fragment?

How does the O-H stretch in the IR spectrum of a carboxylic acid differ from the O-H stretch of an alcohol?

In an IR spectrometer, the ________ uses prisms or diffraction gratings to allow only one frequency of light to enter the detector at a time.

Which IR band is typically more intense, the C≡C stretch or the C≡N stretch? Explain briefly.

Which of the following does not have a broad absorption with one or more spikes that is centered about 3300 cm-1 in the IR?

Provide an equation which relates the energy of a photon to its wavelength.

Ethyne (HC CH) does not show IR absorption in the region 2000-2500 cm-1 because ________.

Which of the following molecules has a characteristic stretch at 2250 cm-1?

How could IR spectroscopy be used to distinguish between the following pair of compounds? CH2 CHCH2CH(CH3)2 and CH3CH2CH2CH(CH3)2

In order for a vibration mode to be observable in the IR, the vibration must change the ________ of the molecule.

Structure and Bonding

Acids and Bases; Functional Groups

Structure and Stereochemistry of Alkanes

The Study of Chemical Reactions

Stereochemistry

Alkyl Halides; Nucleophilic Substitution

Structure and Synthesis of Alkenes; Elimination

Reactions of Alkenes

Structure and Synthesis of Alcohols

Reactions of Alcohols

Nuclear Magnetic Resonance Spectroscopy

Ethers, Epoxides, and Thioethers

Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy

Aromatic Compounds

Reactions of Aromatic Compounds

Ketones and Aldehydes

Amines

Carboxylic Acids

Carboxylic Acid Derivatives

Condensations and Alpha Substitutions of Carboxyl Compounds

Carbohydrates and Nucleic Acids

Amino Acids, Peptides, and Proteins

Lipids

Synthetic Polymers

Filters

Which compound would be expected to show intense IR absorption at 1640 cm^-1?

Deduce a possible structure for the compound with the IR absorptions below. C₄H₈O: 2950, 2820, 2715, 1715 cm^-1

Which of the following does not have a broad absorption with one or more spikes that is centered about 3300 cm^-1 in the IR?

Ethyne (HC CH) does not show IR absorption in the region 2000-2500 cm^-1 because ________.

Which of the following molecules has a characteristic stretch at 2250 cm^-1?

How could IR spectroscopy be used to distinguish between the following pair of compounds? CH₂ CHCH₂CH(CH₃)₂ and CH₃CH₂CH₂CH(CH₃)₂