Deck 20: Dienes, Conjugated Systems, and Pericyclic Reactions

Question 1

What is (are) the major organic product(s) formed in the following reaction?

A) only 1
B) only 1 and 2
C) only 1 and 3
D) only 2 and 4

Answer 1

only 1 and 2

Question 2

Which of the following arrangements of p atomic orbitals gives the lowest energy p-bonding molecular orbital of 1,3-butadiene?

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

Answer 2

2

Question 3

What is the correct order of exothermicity for hydrogenation of the following hexadienes upon treatment with H₂/Pd (more exothermic > less exothermic)?

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

Answer 3

3 > 1 > 2

Question 4

What is (are) the major organic product(s) formed in the following reaction?

A) only 1
B) only 2
C) only 1 and 3
D) only 2 and 4

Question 5

Which of the following terms describes the mechanism for the addition of Br₂ to butadiene?

A) electrophilic addition
B) nucleophilic addition
C) pericyclic addition
D) conjugate addition

Question 6

What is (are) the major organic product(s) formed in the following reaction?

A) only 1
B) only 1 and 3
C) only 2 and 4
D) only 1 and 4

Question 7

Which of the following is(are) formed upon addition of 1 mol of Br₂ to 1,3-cyclohexane?

A) only 2
B) only 1 and 3
C) only 2 and 4
D) 1, 2 and 3

Question 8

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

A) 3,4-dibromo-1-butene
B) (E)-1,4-dibromo-2-butene
C) (Z)-1,4-dibromo-2-butene
D) (Z)-2,3-dibromo-2-butene

Question 9

Which of the following are conjugated dienes?

A) only 1
B) only 2
C) only 1 and 2
D) 1, 2 and 3

Question 10

What is the IUPAC name of the following compound?

A) (R)-3-vinyl-1-butene
B) 3-methyl-1,5-pentadiene
C) 3-methyl-1,4-pentadiene
D) (R)-3-methyl-1,4-pentadiene

Question 11

What is the systematic IUPAC name of the following compound?

A) (3S,4E)-3-ethyl-3,4-dimethyl-1,4-hexadiene
B) (3R,4E)-3-ethyl-3,4-dimethyl-1,4-hexadiene
C) (3S,4Z)-3-ethyl-3,4-dimethyl-1,4-hexadiene
D) (3R,4Z)-3-ethyl-3,4-dimethyl-1,4-hexadiene

Question 12

Which of the following arrangements of p atomic orbitals gives the highest energy p-antibonding molecular orbital of 1,3-butadiene?

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

Question 13

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

A) 3,4-dibromo-1-butene
B) (E)-1,4-dibromo-2-butene
C) (Z)-1,4-dibromo-2-butene
D) (Z)-2,3-dibromo-2-butene

Question 14

What is (are) the major organic product(s) formed in the following reaction?

A) only 1
B) only 3
C) only 1 and 3
D) only 2 and 4

Question 15

What is the reactive intermediate in the reaction of 1,3-butadiene with HBr resulting in 1,2-addition?

A) cyclic bromonium cation
B) allylic cation
C) allylic radical
D) dienophile

Question 16

Which of the following arrangements of p atomic orbitals of 1,3-butadiene has the greatest number of nodes?

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

Question 17

What is the IUPAC name of the following compound?

A) 2,3-dimethyl-2,4-pentadiene
B) (Z)-2,3-dimethyl-2,4-pentadiene
C) 3,4-dimethyl-1,3-pentadiene
D) (Z)-3,4-dimethyl-1,3-pentadiene

Question 18

Which of the following are conjugated dienes?

A) only 1
B) only 2
C) only 1 and 2
D) 1, 2 and 3

Question 19

Which of the following is not a major organic product obtained from the addition of 1 mole of bromine to (E)-1,3-pentadiene?

A) (E)-4,5-dibromo-2-pentene
B) 3,4-dibromo-1-pentene
C) (E)-1,4-dibromo-2-pentene
D) (E)-1,2-dibromo-2-pentene

Question 20

Which of the following alkenes undergoes the least exothermic hydrogenation upon treatment with H₂/Pd

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

Question 21

What are the units of e in ultraviolet-visible spectroscopy?

A) M^-1*cm^-1
B) M*cm
C) J*mol^-1*M^-1
D) none, e is a dimensionless quantity

Question 22

What is the IUPAC name of the following compound?

Question 23

Which of the following laws relates absorbance to the concentration of a sample and the pathlength in ultraviolet-visible spectroscopy?

A) Buzz-Beer law
B) Beer-Lambert law
C) Duff-Beer law
D) Christopher-Lambert law

Question 24

What are the units of l_max in ultraviolet-visible spectroscopy?

A) J*mol^-1
B) M^-1
C) nm
D) none, l_max is a dimensionless quantity

Question 25

What are the two major organic products obtained from the following reaction?

Question 26

What range of wavelengths corresponds to the ultraviolet region of the electromagnetic spectrum?

A) 200-400 nm
B) 400-700 nm
C) 2.5-25 mm
D) 2-10 mm

Question 27

Which of the following electronic transitions is apparent in the ultraviolet-visible spectrum of 1,3-butadiene?

A) n→p*
B) p→p *
C) s→p *
D) s→p

Question 28

Which of the following processes takes place upon absorption of ultraviolet-visible radiation?

A) bond vibration
B) electron excitation
C) nuclear spin flip
D) electron spin flip

Question 29

What is the IUPAC name of the following compound?

Question 30

What is (are) the major organic product(s) formed in the following reaction?

A) only 1
B) only 2
C) only 3
D) 1, 2 and 3

Question 31

Which of the following electronic transitions is (are) apparent in the ultraviolet-visible spectrum of acrolein, H₂C=CHCHO?
1.n→p*
2.p→p*
3.s→ p*

A) only 1
B) only 2
C) only 1 and 2
D) 1, 2 and 3

Question 32

Which of the following energy diagrams represents the electronic state of butadiene after absorption of radiation?

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

Question 33

Which of the following has the highest value of l_max in the ultraviolet-visible spectrum?

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

Question 34

What are the units of absorbance, A, in ultraviolet-visible spectroscopy?

A) J*mol^-1
B) nm*mol^-1
C) J*mol^-1*M^-1
D) none, A is a dimensionless quantity

Question 35

What quantity is abbreviated as e in ultraviolet-visible spectroscopy?

A) absorbance
B) molecular absorptivity
C) intensity of transmitted light
D) wavelength of maximum absorbance

Question 36

Which of the following reaction coordinate diagrams explains the formation of different thermodynamic (T) and kinetic products from the same reactants (R)?

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

Question 37

What are the two major organic products obtained from the following reaction?

Question 38

Which of the following has the highest value of l_max in the ultraviolet-visible spectrum?

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

Question 39

Which of the following energy diagrams represents the electronic state of the ground state of 1,3-butadiene?

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

Question 40

Which of the following relationships is not valid as applied to ultraviolet-visible spectroscopy?

A) A = log (I_o/I)
B) A = ecl
C) DE = hn
D) A = l_maxl

Question 41

What is the major organic product obtained from the following reaction?

Question 42

Draw two resonance structures of the reactive intermediate that accounts for the formation of 1,2- and 1,4-addition products upon reaction of 1,3-butadiene with one equivalent of bromine.

Question 43

Provide the structures of the constitutional isomers of the two major organic products obtained from the following reaction?

Question 44

Draw two resonance structures of the reactive intermediate that accounts for the formation of 1,2- and 1,4-addition products upon reaction of 1,3-butadiene with one equivalent of HBr.