Question 1

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

Accepted Answer

A)  C­H 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)  C­H 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 2

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 3

Which compound would be expected to show intense IR absorption at 2820, 2710 and 1705 cm-1?

Accepted Answer

A)  CH3COCH2CH3 
B)  PhCOCH3 
C)  PhCHO 
D)  CH2=CHCOCH3 
A)  CH3COCH2CH3 
B)  PhCOCH3 
C)  PhCHO 
D)  CH2=CHCOCH3

Question 4

In addition to a carbonyl stretch, which of the following molecules exhibits two characteristic stretches at 2700 and 2800 cm-1?

Accepted Answer

A)  (CH3CH2)2CO 
B)  CH3CH2CH2CHO 
C)  CH3CH2CO2CH3 
D)  CH3CH2CH2CO2H 
E)  CH3CH2CH2COCl 
A)  (CH3CH2)2CO 
B)  CH3CH2CH2CHO 
C)  CH3CH2CO2CH3 
D)  CH3CH2CH2CO2H 
E)  CH3CH2CH2COCl

Question 5

Which region of the electromagnetic spectrum, IR or X-ray, is characterized by waves of lower frequency?

Accepted Answer

The answer of Which region of the electromagnetic spectrum, IR...

Question 6

The presence of which element is indicated by a peak at m/z 127 and a characteristic 127-unit gap in the mass spectrum?

Accepted Answer

A)  Br 
B)  Cl 
C)  I 
D)  N 
E)  S 
A)  Br 
B)  Cl 
C)  I 
D)  N 
E)  S

Question 7

Which compound lacks a strong, characteristic IR absorption near 1700 cm-1?

Accepted Answer

A)  CH3CH2CO2H 
B)  CH3CH2CHO 
C)  (CH3CH2)2C=O 
D)  (CH3CH2)2O 
E)  H3CH2CO2CH3 
A)  CH3CH2CO2H 
B)  CH3CH2CHO 
C)  (CH3CH2)2C=O 
D)  (CH3CH2)2O 
E)  H3CH2CO2CH3

Question 8

What IR absorption is characteristic of the C=O stretch in aldehydes?

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 9

Which has the higher speed in a vacuum, ultraviolet or infrared light?

Accepted Answer

They have

Question 10

What IR absorption is characteristic of the carbon-carbon triple bond stretch in alkynes?

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 11

The region of the IR spectrum which contains the most complex vibrations (600-1400 cm-1) is called the ________ region of the spectrum.

Accepted Answer

Question 12

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 13

Which region of the electromagnetic spectrum, radio or visible, is characterized by waves of shorter wavelength?

Accepted Answer

The answer of Which region of the electromagnetic spectrum, radio...

Question 14

An infrared wavelength of 5.81μm is equivalent to a wavenumber of ________ cm-1.

Accepted Answer

Question 15

Absorption of what type of electromagnetic radiation results in electronic transitions?

Accepted Answer

A)  X-rays 
B)  radio waves 
C)  microwaves 
D)  ultraviolet light 
E)  infrared light 
A)  X-rays 
B)  radio waves 
C)  microwaves 
D)  ultraviolet light 
E)  infrared light

Question 16

Which of the following has a C→H stretch that occurs at the highest stretching frequency?

Accepted Answer

A)  hexane 
B)  hex-1-ene 
C)  (
E) -hex-2-ene 
D)  hex-1-yne 
E)  hex-2-yne 
A)  hexane 
B)  hex-1-ene 
C)  (
E) -hex-2-ene 
D)  hex-1-yne 
E)  hex-2-yne

Question 17

Which compound would be expected to show intense IR absorption at 1746 cm-1?

Accepted Answer

A)  CH3CH2OCH2CH3 
B)  CH3CH2CN 
C)  CH3CO2CH2CH3 
D)  CH3CH2SCH3 
A)  CH3CH2OCH2CH3 
B)  CH3CH2CN 
C)  CH3CO2CH2CH3 
D)  CH3CH2SCH3

Question 18

Which compound has a single, weak IR absorption at 3300 cm-1?

Accepted Answer

A)  (CH3CH2)2NH 
B)  CH3CH2CH2OH 
C)  CH3CH2CN 
D)  (CH3CH2)2O 
E)  CH3CH=CHCH3 
A)  (CH3CH2)2NH 
B)  CH3CH2CH2OH 
C)  CH3CH2CN 
D)  (CH3CH2)2O 
E)  CH3CH=CHCH3

Question 19

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 20

How could IR spectroscopy be used to distinguish between the following pair of compounds?
CH3COCH-CHCH2CH3 and CH3COCH2CH2CH-CH2

Accepted Answer

C-O absorption in co

Exam 12: Infrared Spectroscopy and Mass Spectrometry

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

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?

Which compound would be expected to show intense IR absorption at 2820, 2710 and 1705 cm-1?

In addition to a carbonyl stretch, which of the following molecules exhibits two characteristic stretches at 2700 and 2800 cm-1?

Which region of the electromagnetic spectrum, IR or X-ray, is characterized by waves of lower frequency?

The presence of which element is indicated by a peak at m/z 127 and a characteristic 127-unit gap in the mass spectrum?

Which compound lacks a strong, characteristic IR absorption near 1700 cm-1?

What IR absorption is characteristic of the C=O stretch in aldehydes?

Which has the higher speed in a vacuum, ultraviolet or infrared light?

What IR absorption is characteristic of the carbon-carbon triple bond stretch in alkynes?

The region of the IR spectrum which contains the most complex vibrations (600-1400 cm-1) is called the ________ region of the spectrum.

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

Which region of the electromagnetic spectrum, radio or visible, is characterized by waves of shorter wavelength?

An infrared wavelength of 5.81μm is equivalent to a wavenumber of ________ cm-1.

Absorption of what type of electromagnetic radiation results in electronic transitions?

Which of the following has a C→H stretch that occurs at the highest stretching frequency?

Which compound would be expected to show intense IR absorption at 1746 cm-1?

Which compound has a single, weak IR absorption at 3300 cm-1?

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

How could IR spectroscopy be used to distinguish between the following pair of compounds? CH3COCH-CHCH2CH3 and CH3COCH2CH2CH-CH2

Introduction and Review

Structure and Properties of Organic Molecules

Structure and Stereochemistry of Alkanes

The Study of Chemical Reactions

Stereochemistry

Alkyl Halides: Nucleophilic Substitution and Elimination

Structure and Synthesis of Alkenes

Reactions of Alkenes

Alkynes

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

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

Which compound would be expected to show intense IR absorption at 2820, 2710 and 1705 cm^-1?

In addition to a carbonyl stretch, which of the following molecules exhibits two characteristic stretches at 2700 and 2800 cm^-1?

Which compound lacks a strong, characteristic IR absorption near 1700 cm^-1?

The region of the IR spectrum which contains the most complex vibrations (600-1400 cm^-1) is called the ________ region of the spectrum.

An infrared wavelength of 5.81μm is equivalent to a wavenumber of ________ cm^-1.

Which compound would be expected to show intense IR absorption at 1746 cm^-1?

Which compound has a single, weak IR absorption at 3300 cm^-1?

How could IR spectroscopy be used to distinguish between the following pair of compounds? CH₃COCH-CHCH₂CH₃ and CH₃COCH₂CH₂CH-CH₂