Question 1

Absorption of UV-visible energy by a molecule results in:

Accepted Answer

A)  vibrational transitions 
B)  electronic transitions 
C)  rotational transitions 
D)  nuclear transitions 
E)  none of the above 
A)  vibrational transitions 
B)  electronic transitions 
C)  rotational transitions 
D)  nuclear transitions 
E)  none of the above

Question 2

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

Question 3

What is the resonance energy of a system?

Accepted Answer

The extra stability

Question 4

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 5

What is the hybridization of the central carbon of allene (1,2-propadiene)?

Accepted Answer

A)  sp 
B)  sp2 
C)  sp3 
D)  p 
E)  none of the above 
A)  sp 
B)  sp2 
C)  sp3 
D)  p 
E)  none of the above

Question 6

Draw the HOMO of pentadienyl anion.

Accepted Answer

The answer of Draw the HOMO of pentadienyl anion....

Question 7

Is the thermal [4+2] cycloaddition between allyl anion and ethylene an allowed one? To answer, draw the HOMO of allyl anion and the LUMO of ethylene, and comment on the symmetry match of the two.

Accepted Answer

@#IMG-DLM& The cyclo

Question 8

According to the 1,3-butadiene structure below, which positions would be best to place methoxy groups to yield the most reactive dimethoxy-1,3-butadiene isomer in the Diels-Alder reaction?

Accepted Answer

A)  c and d 
B)  a and c 
C)  b and c 
D)  a and d 
E)  a and f 
A)  c and d 
B)  a and c 
C)  b and c 
D)  a and d 
E)  a and f

Question 9

Provide the major organic product of the following reaction.

Accepted Answer

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

Question 10

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 11

Provide the major organic product of the following reaction.

Accepted Answer

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

Question 12

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 13

Draw the s-cis conformation of (E)-1,3-hexadiene.

Accepted Answer

The answer of Draw the s-cis conformation of (E)-1,3-hexadiene....

Question 14

Provide the major organic product of the following reaction.

Accepted Answer

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

Question 15

Consider the possible thermal [4+4] cycloaddition of two molecules of 1,3-butadiene to generate cycloocta-1,5-diene. Show the HOMO/LUMO interaction which would result, and use this interaction to predict whether the proposed cycloaddition could occur.

Accepted Answer

@#IMG-DLM& The cyclo

Question 16

Which compound has the smallest heat of hydrogenation?

Accepted Answer

A)  5-methyl-1,2-hexadiene 
B)  (
E) -5-methyl-1,3-hexadiene 
C)  5-methyl-1,4-hexadiene 
D)  2-methyl-1,5-hexadiene 
E)  (
E) -2-methyl-2,4-hexadiene 
A)  5-methyl-1,2-hexadiene 
B)  (
E) -5-methyl-1,3-hexadiene 
C)  5-methyl-1,4-hexadiene 
D)  2-methyl-1,5-hexadiene 
E)  (
E) -2-methyl-2,4-hexadiene

Question 17

Show how the carbon p orbitals overlap to form the lowest energy π molecular orbital of 1,3-butadiene.

Accepted Answer

The answer of Show how the carbon p orbitals overlap...

Question 18

Provide the structure of the major product which results from 1,4-addition of Br2 to the diene shown below.

Accepted Answer

Question 19

The following Diels-Alder reaction was featured in Tet. Lett. 2011, 960. Predict the structure of the starting materials.

Accepted Answer

The answer of The following Diels-Alder reaction was featured in...

Question 20

Which sequence correctly ranks the following conjugated systems in order of increasing UV 8max absorption values?

Accepted Answer

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

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

Absorption of UV-visible energy by a molecule results in:

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

What is the resonance energy of a system?

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

What is the hybridization of the central carbon of allene (1,2-propadiene)?

Draw the HOMO of pentadienyl anion.

Is the thermal [4+2] cycloaddition between allyl anion and ethylene an allowed one? To answer, draw the HOMO of allyl anion and the LUMO of ethylene, and comment on the symmetry match of the two.

According to the 1,3-butadiene structure below, which positions would be best to place methoxy groups to yield the most reactive dimethoxy-1,3-butadiene isomer in the Diels-Alder reaction?

Provide the major organic product of the following reaction.

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

Provide the major organic product of the following reaction.

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

Draw the s-cis conformation of (E)-1,3-hexadiene.

Provide the major organic product of the following reaction.

Consider the possible thermal [4+4] cycloaddition of two molecules of 1,3-butadiene to generate cycloocta-1,5-diene. Show the HOMO/LUMO interaction which would result, and use this interaction to predict whether the proposed cycloaddition could occur.

Which compound has the smallest heat of hydrogenation?

Show how the carbon p orbitals overlap to form the lowest energy π molecular orbital of 1,3-butadiene.

Provide the structure of the major product which results from 1,4-addition of Br2 to the diene shown below.

The following Diels-Alder reaction was featured in Tet. Lett. 2011, 960. Predict the structure of the starting materials.

Which sequence correctly ranks the following conjugated systems in order of increasing UV 8max absorption values?

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

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

Provide the structure of the major product which results from 1,4-addition of Br₂ to the diene shown below.

Which sequence correctly ranks the following conjugated systems in order of increasing UV 8_max absorption values?