Question 1

Which of the following methods is most suitable for studying conjugation in molecules?

Accepted Answer

A) infrared 
B) NMR 
C) mass spectrometry 
D) X-ray 
E) UV visible 
A) infrared 
B) NMR 
C) mass spectrometry 
D) X-ray 
E) UV visible

Question 2

Which compound would be expected to show intense IR absorption at 3300 cm-1?

Accepted Answer

A) CH3CCCH3 
B) butane 
C) 1-butene 
D) CH3CH2CCH 
A) CH3CCCH3 
B) butane 
C) 1-butene 
D) CH3CH2CCH

Question 3

Deduce a possible structure for the compound with the IR absorptions below.
C3H5N: 3000, 2250 cm-1

Accepted Answer

Question 4

Which of the following molecular changes is necessary for mass spectrometry to occur?

Accepted Answer

A) excitation of an electron from the ground state to higher energy state 
B) change of alignment of an electron in a magnetic field 
C) change of alignment of a proton in a magnetic field 
D) loss of an electron 
E) molecular vibration 
A) excitation of an electron from the ground state to higher energy state 
B) change of alignment of an electron in a magnetic field 
C) change of alignment of a proton in a magnetic field 
D) loss of an electron 
E) molecular vibration

Question 5

Identify the compound with the shortest λmax in an UV spectrum.

Accepted Answer

A) 1-decene 
B) 1,3-decadiene 
C) 1,3,5-decatriene 
D) 1,4-decadiene 
E) 1,3,5,7-decatetraene 
A) 1-decene 
B) 1,3-decadiene 
C) 1,3,5-decatriene 
D) 1,4-decadiene 
E) 1,3,5,7-decatetraene

Question 6

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

Accepted Answer

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

Question 7

Deduce a possible structure for the compound with the IR absorptions below.
C4H8O: 3000, 2800, 2715, 1715 cm-1

Accepted Answer

Question 8

Give the ion that corresponds a m/z ratio of 31 in a mass spectrum of 1-butanol.

Accepted Answer

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

Question 9

Explain how hydrogen bonding affects the shape of O-H and N-H absorption bands in IR spectra.

Accepted Answer

O-H and N-H bands are generally quite br

Question 10

Which compound would be expected to show intense IR absorption at 2250 cm-1?

Accepted Answer

A) CH3CH2CH2CO2H 
B) CH3CH2CH2CN 
C) CH3CH2CH2CH2OH 
D) CH3CH2CH2CONH2 
A) CH3CH2CH2CO2H 
B) CH3CH2CH2CN 
C) CH3CH2CH2CH2OH 
D) CH3CH2CH2CONH2

Question 11

Which of the following regions of the electromagnetic spectrum has the greatest energy per photon?

Accepted Answer

A) visible 
B) microwave 
C) radio 
D) ultraviolet 
E) infrared 
A) visible 
B) microwave 
C) radio 
D) ultraviolet 
E) infrared

Question 12

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 13

How could IR spectroscopy be used to distinguish between the following pair of compounds?
HOCH2CH2CHO and CH3CH2CO2H

Accepted Answer

Carboxylic acid will

Question 14

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

Accepted Answer

High resol

Question 15

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 16

An acylium ion is often produced as a fragment in the MS of which of the following class of organic compounds?

Accepted Answer

A) ketones 
B) ethers 
C) alkyl halides 
D) alcohols 
E) peroxides 
A) ketones 
B) ethers 
C) alkyl halides 
D) alcohols 
E) peroxides

Question 17

Which compound's carbonyl stretch occurs at the greatest wavenumber?

Accepted Answer

A) CH3CH2CH2CHO 
B) CH3COCH2CH3 
C) CH3CH2CONH2 
D) CH3CH2CO2CH3 
E) CH3CH2COCH2CH3 
A) CH3CH2CH2CHO 
B) CH3COCH2CH3 
C) CH3CH2CONH2 
D) CH3CH2CO2CH3 
E) CH3CH2COCH2CH3

Question 18

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

Accepted Answer

C-D; heavier atoms i

Question 19

The pKa of a compound whose acidic or basic form absorbs UV or visible light can be determined spectroscopically since ________.

Accepted Answer

A) lmax always decreases as acidic form is converted to basic 
B) the pKa is the same as the pH at which half of the total absorbance increase occurs 
C) absorbance of the basic form is always twice that of the acidic form 
D) absorbance of the acidic form is always twice that of the basic form 
E) delocalization always leads to a decrease in acidity 
A) lmax always decreases as acidic form is converted to basic 
B) the pKa is the same as the pH at which half of the total absorbance increase occurs 
C) absorbance of the basic form is always twice that of the acidic form 
D) absorbance of the acidic form is always twice that of the basic form 
E) delocalization always leads to a decrease in acidity

Question 20

The mass spectrum of an unknown compound has a molecular ion peak with a relative abundance of 43.27% and an M + 1 peak with a relative abundance of 3.81%. How many carbon atoms are in the compound?

Accepted Answer

# of carbon atoms =

Exam 14: Mass Spectrometry, Infrared Spectroscopy, and Uvvis Spectroscopy

Which of the following methods is most suitable for studying conjugation in molecules?

Which compound would be expected to show intense IR absorption at 3300 cm-1?

Deduce a possible structure for the compound with the IR absorptions below. C3H5N: 3000, 2250 cm-1

Which of the following molecular changes is necessary for mass spectrometry to occur?

Identify the compound with the shortest λmax in an UV spectrum.

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

Deduce a possible structure for the compound with the IR absorptions below. C4H8O: 3000, 2800, 2715, 1715 cm-1

Give the ion that corresponds a m/z ratio of 31 in a mass spectrum of 1-butanol.

Explain how hydrogen bonding affects the shape of O-H and N-H absorption bands in IR spectra.

Which compound would be expected to show intense IR absorption at 2250 cm-1?

Which of the following regions of the electromagnetic spectrum has the greatest energy per photon?

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

How could IR spectroscopy be used to distinguish between the following pair of compounds? HOCH2CH2CHO and CH3CH2CO2H

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

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

An acylium ion is often produced as a fragment in the MS of which of the following class of organic compounds?

Which compound's carbonyl stretch occurs at the greatest wavenumber?

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

The pKa of a compound whose acidic or basic form absorbs UV or visible light can be determined spectroscopically since ________.

The mass spectrum of an unknown compound has a molecular ion peak with a relative abundance of 43.27% and an M + 1 peak with a relative abundance of 3.81%. How many carbon atoms are in the compound?

Remembering General Chemistry: Electronic Structure and Bonding

Acids and Bases: Central to Understanding Organic Chemistry

An Introduction to Organic Compounds

Isomers: the Arrangement of Atoms in Space

Alkenes Thermodynamics and Kinetics

Reactions of Alkenes

Reactions of Alkynes Introduction to Multistep Synthesis

Electron Delocalization, Resonance, and Aromaticity More About Molecular Orbital Theory

Substitution Reactions of Alkyl Halides

Elimination Reactions of Alkyl Halides Competition Between Substitution and Elimination

Reactions of Alcohols, Ethers, Epoxides, and Sulfur-Containing Compounds

Organometallic Compounds

Reactions of Alkanes, Radicals

Nmr Spectroscopy

Reactions of Carboxylic Acids and Carboxylic Acid Derivatives

Reactions of Aldehydes and Ketones

Reactions at the Alpha Carbon of Carbonyl Compounds

Reactions of Benzene and Substituted Benzenes

More About Amines Heterocylic Compounds

Carbohydrates

Amino Acids, Peptides, and Proteins

Catalysis

The Organic Mechanisms of the Coenzymes

The Chemistry of Metabolism

Nucleosides, Nucleotides, and Nucleic Acids

Synthetic Polymers

Pericyclic Reactions

Filters

Which compound would be expected to show intense IR absorption at 3300 cm^-1?

Deduce a possible structure for the compound with the IR absorptions below. C₃H₅N: 3000, 2250 cm^-1

Identify the compound with the shortest λ_max in an UV spectrum.

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

Deduce a possible structure for the compound with the IR absorptions below. C₄H₈O: 3000, 2800, 2715, 1715 cm^-1

Which compound would be expected to show intense IR absorption at 2250 cm^-1?

How could IR spectroscopy be used to distinguish between the following pair of compounds? HOCH₂CH₂CHO and CH₃CH₂CO₂H

The pK_a of a compound whose acidic or basic form absorbs UV or visible light can be determined spectroscopically since ________.