Deck 7: Structure and Synthesis of Alkenes

Question 1

Draw the line energy orbital diagram for the outer shell of an sp² hybridized carbon atom and explain how a carbon/carbon double is formed.

Answer 1

If we follow Hund's rule and fill each orbital with one electron and then promote one to the lone atomic p orbital, there are single electrons in the three sp hybrid orbitals that can form sigma overlaps with 2-H orbitals and one other sp² hybridized carbon orbital. The atomic p orbital with one electron can then form a pi bond by a side to side overlap with the other p orbital from the other sp² hybridized carbon atom.

Question 2

How many elements of unsaturation are implied by the molecular formula C₇H₁₁Cl?

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

Answer 2

2

Question 3

Which of the following molecular formulas corresponds to a monocyclic saturated compound?

A) C₆H₆
B) C₃H₇Br
C) C₃H₇N
D) C₃H₈O

Answer 3

C₃H₇N

Question 4

How many elements of unsaturation are implied by the molecular formula C₅H₈O?

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

Question 5

Which of the following best approximates the CCC bond angle of propene?

A) 90°
B) 109°
C) 120°
D) 150°
E) 180°

Question 6

A newly isolated natural product was found to have the molecular formula C₁₅H₂₈O₂. By hydrogenating a sample of the compound, it was determined to possess one p bond. How many rings are present in the compound?

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

Question 7

Consider molecules with the formula C₁₀H₁₆. Which of the following structural features are not possible within this set of molecules?

A) 2 triple bonds
B) 1 ring and 1 triple bond
C) 2 rings and 1 double bond
D) 2 double bonds and 1 ring
E) 3 double bonds

Question 8

The steroid testosterone has the molecular formula C₁₉H₂₈O₂. Given that there are two P -bond in a molecule of testosterone, how many rings are present in each molecule?

A) 2
B) 3
C) 4
D) 5
E) 6

Question 9

How many elements of unsaturation do molecules with a molecular formula of C₆H₆Cl₆ have?

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

Question 10

The prostaglandin precursor arachidonic acid has the molecular formula C₂₀H₃₂O₂. Given that arachidonic acid is an acyclic carboxylic acid that contains no carbon-carbon triple bonds, how many carbon-carbon double bonds are present?

A) 2
B) 3
C) 4
D) 5
E) 6

Question 11

What two atomic orbitals or hybrid atomic orbitals overlap to form the C­C π bond in ethylene?

A) C sp³ + C sp³
B) C sp³ + C sp²
C) C sp² + C sp²
D) C sp² + C p
E) C p + C p

Question 12

Which of the following statements best describes the relative bond dissociation energies of the sigma and pi bonds present in the carbon-carbon double bond of an alkene?

A) sigma > pi
B) pi > sigma
C) sigma = pi
D) cannot be estimated

Question 13

What two atomic orbitals or hybrid atomic orbitals overlap to form the C­C σ bond in ethylene?

A) C sp³ + C sp³
B) C sp³ + C sp²
C) C sp² + C sp²
D) C sp³ + C p
E) C sp² + C p

Question 14

What two atomic orbitals or hybrid atomic orbitals overlap to form the C­H bond in ethylene?

A) C sp³ + H s
B) C sp² + H s
C) C sp + H s
D) C p + H s

Question 15

Circle all atoms that are coplanar in the molecule below.

Question 16

How many elements of unsaturation do molecules with a molecular formula of C₈H₄N₂ have?

A) 2
B) 4
C) 6
D) 8
E) 10

Question 17

How many elements of unsaturation are implied by the molecular formula C₆H₁₂?

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

Question 18

The carbon-carbon bond length in ethylene is ________ than the carbon-carbon bond length in ethane, and the HCH bond angle in ethylene is ________ the HCH bond angle in ethane

A) shorter; smaller than
B) shorter; larger than
C) longer; smaller than
D) longer; larger than
E) longer; the same as

Question 19

Why is rotation about the carbon-carbon double bond in alkenes prohibited while relatively free rotation can occur about the carbon-carbon single bond in alkanes?

Question 20

Carbon-carbon single bonds tend to be ________ and ________ than carbon-carbon double bonds.

A) shorter, stronger
B) longer, stronger
C) shorter, weaker
D) longer, weaker

Question 21

Draw an acceptable structure for 4-ethylhept-1-ene.

Question 22

Draw and name all alkenes which have the molecular formula C₄H₈.

Question 23

Provide a correct IUPAC name for the structure below.

Question 24

A chemist has isolated a new natural product and determined its molecular formula to be C₂₄H₄₀O₄. In hydrogenation experiments the chemist found that each mole of the natural product reacted with two moles of H₂. How many rings are present in the structure of the new natural product?

A) 2
B) 3
C) 4
D) 5
E) 6

Question 25

Provide the proper IUPAC name for the alkene shown below.

Question 26

Which of the following alkenes can show geometric isomerism: 2,3-dichloro-2-pentene, 4-chloro-3-ethyl-3-hexene, 3-chloro-2-methyl-2-butene, and 3-chloro-2-methyl-1-butene?

Question 27

Draw an acceptable structure for 1,2-dimethylcyclohexene.

Question 28

Draw an acceptable structure for 4-phenylbut-1-ene.

Question 29

Identify the correct name for the following structure.

A) 3-methoxy-5-methylcyclohepta-1,5-diene
B) 6-methoxy-1-methylcyclohepta-1,4-diene
C) 7-methoxy-5-methylcyclohepta-1,4-diene
D) 4-methoxy-2-methylcyclohepta-1,5-diene

Question 30

Provide an acceptable name for (CH₃CH₂)₂CHCH₂CH=CH₂.

Question 31

Provide the proper IUPAC name for the alkene shown below.
CH₂=CHCH₂CH₂CH₂CH₃

Question 32

How many elements of unsaturation are implied by the molecular formula C₅H₅NO₂?

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

Question 33

Name the alkene shown. Be sure to include the appropriate E or Z label necessary.

Question 34

Provide an acceptable name for (CH₃)₂CHCH=C(CH₃)CH₂CH₃.

Question 35

Provide the proper IUPAC name for the alkene shown below.

Question 36

Draw and name the six alkenes which have the molecular formula C₅H₁₀.

Question 37

Provide the proper IUPAC name for the alkene shown below.

Question 38

Name the compound shown below.

Question 39

How many elements of unsaturation are implied by the molecular formula C₈H₁₁N?

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

Question 40

For which of the following alkenes will cis- and trans- isomers not exist?

A) a) only
B) b) only
C) both a) and c)
D) d) only
E) both c) and d)

Question 41

Which of the following best describes the geometry about the carbon-carbon double bond in the alkene below?

A) E
B) Z
C) neither E nor Z

Question 42

Which of the following best describes the geometry about the carbon-carbon double bond in the alkene below?

A) E
B) Z
C) neither E nor Z

Question 43

Which of the following best describes the geometry about the carbon-carbon double bond in the alkene below?

A) E
B) Z
C) neither E nor Z

Question 44

Which has the smaller heat of hydrogenation, (E)-2-pentene or (Z)-2-pentene? What is the structural origin of this difference?

Question 45

Draw the structure of polyethylene.

Question 46

Circle the alkene below which has the smallest heat of hydrogenation.

Question 47

Provide the proper IUPAC name for the alkene shown below.

Question 48

Provide the proper IUPAC name for the alkene shown below.

Question 49

Provide the proper IUPAC name for the alkene shown below.

Question 50

Draw an acceptable structure for (Z)-2-chloro-4-ethylhex-2-ene.

Question 51

Which of the following best describes the geometry about the carbon-carbon double bond in the alkene below?

A) E
B) Z
C) neither E nor Z

Question 52

Translate the following condensed structure to a line-angle structure.
(E) CH₃CBrCH(CH₂)₂C(O)CH(CH₃)₂

Question 53

The compound produced when 3-methylpent-2-ene undergoes hydrogenation in the presence of a platinum catalyst is ________.

Question 54

Provide the structure of the monomer from which PVC or poly(vinyl chloride) is made.

Question 55

Provide a structure for (Z)-4-bromo-3-heptene.

Question 56

Name the alkene shown. Be sure to include the appropriate E or Z label necessary.

Question 57

Provide the structure of (Z)-1-chloro-1-fluoro-1-butene.

Question 58

Draw the structure of poly(tetrafluoroethylene) or Teflon.

Question 59

Provide the proper IUPAC name for the alkene shown below.

Question 60

Which of the following best describes the geometry about the carbon-carbon double bond in the alkene below?

A) E
B) Z
C) neither E nor Z

Question 61

Draw the alkene of formula C₅H₁₀ which evolves the most heat per mole upon hydrogenation.

Question 62

Compare the relative heats of hydrogenation of cyclobutene and cyclopentene and explain the difference in magnitude.

Question 63

The trans isomers of cycloalkenes with rings containing fewer than ________ atoms are unstable at room temperature.

Question 64

Does the alkene shown below violate Bredt's rule?

Question 65

Which sequence ranks the following compounds in order of increasing heat of hydrogenation, ΔH_hyd?
1. cis-2-butene
2. 1-butene
3. cyclohexene

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

Question 66

Circle the most stable alkene in the set of isomers below.

Question 67

Using Zaitsev's rule, choose the most stable alkene among the following.

A) 1,2-dimethylcyclohexene
B) 1,6-dimethylcyclohexene
C) cis-3,4-dimethylcyclohexene
D) They are all of equal stability according to Zaitsev's rule.

Question 68

Circle the alkene isomer that has the largest heat of hydrogenation.

Question 69

Circle the most stable alkene in the set of isomers below.

Question 70

Which of the following alkenes has the largest molar heat of hydrogenation (ie, releases the most heat upon hydrogenation)?

A) 2,3-dimethyl-2-butene
B) 2-methyl-2-butene
C) $\underline{\text{ trans }}$ -2-butene
D) $\underline{\text{ cis }}$ -2-butene
E) 1-hexene

Question 71

Which of the following cycloalkenes would be expected to be stable?

A) 1 & 2
B) 2 & 3
C) 2
D) 1 & 3
E) None are stable.

Question 72

Using Zaitsev's rule, choose the most stable alkene among the following.

A) hex-1-ene
B) (E)-hex-2-ene
C) (Z)-hex-2-ene
D) They are all of equal stability according to Zaitsev's rule.

Question 73

There are three isomeric methylbutene structures. Draw each of them and then circle the isomer with the highest heat of hydrogenation.

Question 74

Does the alkene shown below violate Bredt's rule?

Question 75

Draw all likely alkene products in the following reaction and circle the product you expect to predominate.

Question 76

Does the alkene shown below violate Bredt's rule?

Question 77

Using Zaitsev's rule, choose the most stable alkene among the following.

A) 1-methylcyclohexene
B) 3-methylcyclohexene
C) 4-methylcyclohexene
D) They are all of equal stability according to Zaitsev's rule.

Question 78

Which of the following alkenes has the smallest molar heat of hydrogenation (ie, releases the least heat upon hydrogenation)?

A) 2,3-dimethyl-2-butene
B) 2-methyl-2-butene
C) $\underline{\text{ trans }}$ -2-butene
D) $\underline{\text{ cis }}$ -2-butene
E) 1-hexene

Question 79

Does the alkene shown below violate Bredt's rule?

Question 80

Consider the constitutional isomers 2-methylbut-1-ene, 2-methylbut-2-ene, and 3-methylbut-1-ene. When each of these alkenes is subjected to catalytic hydrogenation (H₂, Pt), a single product results. Which of the following best describes the structural relationship among these products?

A) The products are cis-trans isomers.
B) The products are identical.
C) The products are constitutional isomers.
D) The products are enantiomers.
E) The products are diastereomers.