Deck 16: Conjugation, Resonance, and Dienes

Question 1

Rank the following dienes in order of increasing reactivity in a Diels-Alder reaction, listing the least reactive first.

A)I< II < III
B)III < I < II
C)II < I < III
D)I < III < II

Answer 1

III < I < II

Question 2

Which of the following statements about resonance structures is true?

A)The placement of atoms is different.
B)The placement of p bonds is different.
C)The placement of s bonds is different.
D)The placement of nonbonded electrons is the same.

Answer 2

The placement of p bonds is different.

Question 3

Rank the following compounds in order of increasing stability, putting the least stable first.

A)I< II < III
B)III < II < I
C)II < I < III
D)III < I < II

Answer 3

I< II < III

Question 4

Which of the following statements about the Diels-Alder reaction is true?

A)The diene can react only when it adopts the s-trans conformation.
B)Electron-withdrawing substituents in the diene increase reaction rate.
C)Electron-donating substituents in the dienophile increase the reaction rate.
D)The stereochemistry of the dienophile is retained in the product.

Question 5

Which of the following is (are) conjugated dienes?

A)Only I
B)Only II
C)Only I and II
D)I, II, and III

Question 6

Which of the following statements about the mechanism of the Diels-Alder reaction is true?

A)Three π bonds break; two σ bonds and one π bond form.
B)Three π bonds break; one σ bond and two π bonds form.
C)Two π bonds break; one σ bond and one π bond form.
D)Two π bonds break; two σ bonds and one π bond form.

Question 7

Which of the following is the least reactive diene in a Diels-Alder reaction?

A)I
B)II
C)III
D)IV

Question 8

What is the thermodynamic product obtained from the addition of 1 equivalent of HBr to 1,3-butadiene?

A)3-Bromo-1-butene
B)1-Bromo-2-butene
C)2-Bromo-2-butene
D)2-Bromo-1-butene

Question 9

What is (are) the major product(s) of the following reaction?

A)Only I
B)Only II
C)Only I and II
D)I, II, and III

Question 10

What is (are) the major product(s) of the following reaction?

A)Only I
B)Only II and IV
C)Only I and III
D)Only I, II, and III

Question 11

Which of the following dienes contain conjugated double bonds?

A)Only I and II
B)Only II and III
C)Only I and III
D)Only II and IV

Question 12

Which of the following is not a product obtained from the addition of 1 equivalent of HBr to (E)-1,3-pentadiene?

A)(E)-4-Bromo-2-pentene
B)(E)-1-Bromo-2-pentene
C)3-Bromo-1-pentene
D)(E)-3-Bromo-2-pentene

Question 13

What is (are) the major product(s) of the following reaction?

A)Only I
B)Only I and III
C)Only II and IV
D)Only I, II, and III

Question 14

Which of the following is not a feature of the Diels-Alder reaction?

A)They are initiated by peroxides.
B)They form new six-membered rings.
C)Three π bonds break.
D)They are concerted.

Question 15

What is the kinetic product obtained from the addition of 1 equivalent of HBr to 1,3-butadiene?

A)3-Bromo-1-butene
B)1-Bromo-2-butene
C)2-Bromo-2-butene
D)2-Bromo-1-butene

Question 16

Which of the following is the appropriate term for the mechanism of the addition of HBr to 1,3-dienes?

A)Nucleophilic addition
B)Electrophilic addition
C)Free radical addition
D)Conjugate addition

Question 17

Which of the following statements about kinetic vs.thermodynamic products is true?

A)The product that is formed faster is the thermodynamic product.
B)The kinetic product predominates at low temperature.
C)The product that predominates at equilibrium is the kinetic product.
D)The thermodynamic product is less stable.

Question 18

What is the reactive intermediate in the reaction of 1,3-diene with HBr, resulting in 1,4-addition?

A)Allylic radical
B)Cyclic bromonium
C)Dienophile
D)Allylic carbocation

Question 19

What is the hybridization around the indicated carbon atom in the following anion?

A)sp³
B)sp²
C)sp
D)p

Question 20

Which of the following conjugated dienes represent two conformations?

A)Only I and II
B)Only I and III
C)Only II and III
D)None of the choices

Question 21

Rank the following dienophile in order of increasing reactivity in a Diels-Alder reaction, listing the least reactive first.

A)I< II < III
B)III < I < II
C)II < I < III
D)III < II < I

Question 22

Which of the following compounds is the least reactive dienophile in a Diels-Alder reaction?

A)I
B)II
C)III
D)IV

Question 23

Which of the following is the most reactive diene in a Diels-Alder reaction?

A)I
B)II
C)III
D)IV

Question 24

What is the major organic product of the following reaction?

A)I
B)II
C)III
D)IV

Question 25

Why would the compound below not react with a dienophile in a Diels-Alder reaction?

A)The compound is not a conjugated diene.
B)There are no electron withdrawing groups on the compound.
C)There are no electron donating groups on the compound.
D)The compound cannot adopt the s-cis conformation.

Question 26

Which of the following electronic transitions is common in the UV spectrum of 1,3-butadiene?

A)sp
B)sp*
C)n p*
D)pp*

Question 27

What is the definition of a resonance structure?

A)Compounds with the same molecular formula.
B)Compounds with different carbon frameworks.
C)Structures that differ only in the placement of π and nonbonding electrons.
D)Structures that differ only in the location of bonds.

Question 28

Which of the following compound absorbs UV light at the longest wavelength?

A)I
B)II
C)III
D)IV

Question 29

Which of the following compounds is the most reactive dienophile in a Diels-Alder reaction?

A)I
B)II
C)III
D)IV

Question 30

Which of the following is an example of a bridged bicyclic system?

A)I
B)II
C)III
D)IV

Question 31

What is the major organic product of the following reaction?

A)I
B)II
C)III
D)IV

Question 32

What is the major organic product of the following reaction?

A)I
B)II
C)III
D)IV

Question 33

Which of the following is the least reactive diene in a Diels-Alder reaction?

A)I
B)II
C)III
D)IV

Question 34

What is the major organic product of the following reaction?

A)Only I
B)Only II
C)Only III
D)Only I and II

Question 35

Which of the following is not a resonance structure of acetic anhydride?

A)I
B)II
C)III
D)IV

Question 36

Rank the following anions from most to least stable, listing the most stable first.

A)I> II > III
B)III > II > I
C)I > III > II
D)III > I > II

Question 37

What diene and dienophile are used in a Diels-Alder reaction to prepare the following compound?

A)I
B)II
C)III
D)IV

Question 38

What is the major organic product of the following reaction?

A)Only I
B)Only I and II
C)Only II and III
D)I, II, and III

Question 39

What is the major organic product of the following reaction?

A)Only I
B)Only II
C)Only III
D)Only I and II

Question 40

Which of the following compound absorbs UV light at the longest wavelength?

A)I
B)II
C)III
D)IV

Question 41

Which triene absorbs the longest wavelength of UV light?

A)I
B)II
C)III
D)IV

Question 42

Which triene has the smallest heat of hydrogenation?

A)I
B)II
C)III
D)IV

Question 43

Which triene has the largest heat of hydrogenation?

A)I
B)II
C)III
D)IV