Question 1

Draw the LUMO of 1,3-butadiene.

Accepted Answer

The answer of Draw the LUMO of 1,3-butadiene....

Question 2

Draw the HOMO of 1,3-butadiene.

Accepted Answer

The answer of Draw the HOMO of 1,3-butadiene....

Question 3

What diene and dienophile would react to give the product below?

Accepted Answer

The answer of What diene and dienophile would react to...

Question 4

The number of π molecular orbitals in a molecule is always equal to the number of ________.

Accepted Answer

A)  π bonds 
B)  p orbitals used to construct the π bonds 
C)  electrons in the π system 
D)  hydrogen atoms in the molecule 
A)  π bonds 
B)  p orbitals used to construct the π bonds 
C)  electrons in the π system 
D)  hydrogen atoms in the molecule

Question 5

In the UV-visible spectrum of (E)-1,3,5-hexatriene, the lowest energy absorption corresponds to a ________.

Accepted Answer

A)  σ to π transition 
B)  σ to π* transition 
C)  π to σ* transition 
D)  σ to σ* transition 
E)  π to π* transition 
A)  σ to π transition 
B)  σ to π* transition 
C)  π to σ* transition 
D)  σ to σ* transition 
E)  π to π* transition

Question 6

Draw the 2 organic products expected from this reaction, label them as thermodynamic or kinetic and tell which predominates at -80°C.

Accepted Answer

The answer of Draw the 2 organic products expected from...

Question 7

Show how the reaction of an allylic halide with a Grignard reagent might be used to synthesize the following:

Accepted Answer

The answer of Show how the reaction of an allylic...

Question 8

What is the resonance energy of a system?

Accepted Answer

The extra stability

Question 9

Give a representation of the lowest occupied π MO of 1,3-butadiene in its ground state.

Accepted Answer

The answer of Give a representation of the lowest occupied...

Question 10

Draw mechanism for the following reaction:

Accepted Answer

The answer of Draw mechanism for the following reaction: ...

Question 11

Which of the following compounds absorbs the longest wavelength of UV-visible light?

Accepted Answer

A)  (
E) -but-2-ene 
B)  (Z)-but-2-ene 
C)  hex-1-ene 
D)  (Z)-1,3-hexadiene 
E)  (
E) -1,3,5-hexatriene 
A)  (
E) -but-2-ene 
B)  (Z)-but-2-ene 
C)  hex-1-ene 
D)  (Z)-1,3-hexadiene 
E)  (
E) -1,3,5-hexatriene

Question 12

UV spectroscopy measures the energy required to promote an electron from the ________ molecular orbital to the ________ molecular orbital.

Accepted Answer

A)  highest occupied, lowest unoccupied 
B)  lowest occupied, lowest unoccupied 
C)  lowest occupied, highest unoccupied 
D)  highest occupied, highest unoccupied 
E)  None of the above 
A)  highest occupied, lowest unoccupied 
B)  lowest occupied, lowest unoccupied 
C)  lowest occupied, highest unoccupied 
D)  highest occupied, highest unoccupied 
E)  None of the above

Question 13

Which sequence correctly ranks the following dienes in order of increasing reactivity in the Diels-Alder reaction?

Accepted Answer

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

Question 14

What are the structures of A, B, and C?

Accepted Answer

The answer of What are the structures of A, B,...

Question 15

How many molecular orbitals are needed to represent the conjugated π system of β-carotene?

Accepted Answer

A)  1 
B)  10 
C)  11 
D)  20 
E)  22 
A)  1 
B)  10 
C)  11 
D)  20 
E)  22

Question 16

Why does the (E,E)-isomer of 2,4-hexadiene react much more rapidly with dienophiles than does the (Z,Z)-isomer?

Accepted Answer

The s-cis conformation, which

Question 17

Draw (Z)-1,3-hexadiene in its s-trans conformation.

Accepted Answer

The answer of Draw (Z)-1,3-hexadiene in its s-trans conformation....

Question 18

Which of the following alkyl halides yields the most stable carbocation intermediate during solvolysis in hot ethanol?

Accepted Answer

A)  methyl iodide 
B)  (S)-2-bromopentane 
C)  (R)-2-bromopentane 
D)  (S)-3-bromopent-1-ene 
E)  1-chlorobutane 
A)  methyl iodide 
B)  (S)-2-bromopentane 
C)  (R)-2-bromopentane 
D)  (S)-3-bromopent-1-ene 
E)  1-chlorobutane

Question 19

Provide the structure of the major organic product in the following reaction.

Accepted Answer

The answer of Provide the structure of the major organic...

Question 20

How many electrons are present in the nonbonding π molecular orbital of the allyl cation?

Accepted Answer

A)  0 
B)  1 
C)  2 
D)  3 
E)  4 
A)  0 
B)  1 
C)  2 
D)  3 
E)  4

Exam 15: Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy

Draw the LUMO of 1,3-butadiene.

Draw the HOMO of 1,3-butadiene.

What diene and dienophile would react to give the product below?

The number of π molecular orbitals in a molecule is always equal to the number of ________.

In the UV-visible spectrum of (E)-1,3,5-hexatriene, the lowest energy absorption corresponds to a ________.

Draw the 2 organic products expected from this reaction, label them as thermodynamic or kinetic and tell which predominates at -80°C.

Show how the reaction of an allylic halide with a Grignard reagent might be used to synthesize the following:

What is the resonance energy of a system?

Give a representation of the lowest occupied π MO of 1,3-butadiene in its ground state.

Draw mechanism for the following reaction:

Which of the following compounds absorbs the longest wavelength of UV-visible light?

UV spectroscopy measures the energy required to promote an electron from the ________ molecular orbital to the ________ molecular orbital.

Which sequence correctly ranks the following dienes in order of increasing reactivity in the Diels-Alder reaction?

What are the structures of A, B, and C?

How many molecular orbitals are needed to represent the conjugated π system of β-carotene?

Why does the (E,E)-isomer of 2,4-hexadiene react much more rapidly with dienophiles than does the (Z,Z)-isomer?

Draw (Z)-1,3-hexadiene in its s-trans conformation.

Which of the following alkyl halides yields the most stable carbocation intermediate during solvolysis in hot ethanol?

Provide the structure of the major organic product in the following reaction.

How many electrons are present in the nonbonding π molecular orbital of the allyl cation?

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

Infrared Spectroscopy and Mass Spectrometry

Nuclear Magnetic Resonance Spectroscopy

Ethers, Epoxides, and Thioethers

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

UV spectroscopy measures the energy required to promote an electron from the molecular orbital to the molecular orbital.