Deck 8: Reactions of Alkenes and Alkynes

Question 1

How many isomeric products would be formed when the following compound undergoes dehydration?

A) 1
B) 2
C) 3
D) 4
E) 5

Answer 1

5

Question 2

The reaction conditions to carry out the production of cyclopentene using bromocyclopentane as the starting material would be:

A) KOH, CH₃CH₂OH
B) H₂SO₄, THF
C) H₂O₂, OH−
D) Hg(OAc)₂,H₂O

Answer 2

KOH, CH₃CH₂OH

Question 3

Compare the products when the following compound reacts with Br₂ in the presence of an organic solvent versus water.

Answer 3

Organic solvent − bromination Water − halohydrin formation In an organic solvent halogenation of the alkene will occur producing a halogenated alkane, while in water (another nucleophile) the product formed would be the halohydrin.

Question 4

The product(s) of the reaction when carried out in an organic solvent would be:

A) cis-1,2-dibromocyclohexane only
B) trans-1,2-dibromocyclohexane only
C) 50/50 mixture of cis-1,2-dibromocyclohexane and trans-1,2-dibromocyclohexane only
D) mixture with > 50% being trans-1,2-dibromocyclohexane only

Question 5

The reaction of 2-methylpropene with HBr in ether gives one of the two products below. Answer the following question(s) about this reaction.
Refer to instructions. The reaction mixture would contain a majority of which isomeric product?

Question 6

Consider the reaction sequence below to answer the following question.
Refer to instructions. Write the complete reaction mechanism for the first step of this reaction sequence. Show all electron flow with arrows and show all intermediate structures.

Question 7

Predict the products of each reaction below. Indicate regiochemistry and stereochemistry when relevant.
Predict and indicate:

Question 8

Predict the structure of the alkene you would use to prepare the alkyl halide below.
Predict:

Question 9

Which set of reagents is used for the Markovnikov addition of water to an alkene without rearrangement?

A) BH₃, THF followed by H₂O₂, NaOH
B) H₂O, H₂SO₄
C) Hg(O₂CCH₃)₂, H₂O followed by NaBH₄, NaOH
D) none of these

Question 10

For each reaction below, suggest structures for alkenes that give the indicated reaction products. There may be more than one answer.
Suggest structure(s):

Question 11

What is the major product of this reaction?

Question 12

The reaction of 2-methylpropene with HBr in ether gives one of the two products below. Answer the following question(s) about this reaction.
Refer to instructions. Which product is the Markovnikov product?

Question 13

To answer the question(s) below, consider the following reaction:
When cyclohexene reacts with chlorine in tetrachloromethane, the trans-dihalide is formed.
Refer to instructions. Write the complete, stepwise mechanism for this reaction. Show all intermediate structures and all electron flow using arrows.

Question 14

For each reaction below, suggest structures for alkenes that give the indicated reaction products. There may be more than one answer.
Suggest structure(s):

Question 15

Predict the products of each reaction below. Indicate regiochemistry and stereochemistry when relevant.
Predict and indicate:
a) b)If the product of the above reaction were subsequently treated with periodic acid (HIO₄), write the formula for the product formed.

Question 16

Predict the product of the reaction below. Indicate regiochemistry and stereochemistry if relevant. (D₂ = deuterium)

Question 17

The reaction of 2-methylpropene with HBr in ether gives one of the two products below. Answer the following question(s) about this reaction.
Refer to instructions. Which product would have a lower energy transition state for the formation of the intermediate leading to it?

Question 18

Consider the reaction below to answer the following question(s).
Alkenes may be hydrated by the hydroboration/oxidation procedure shown.
Refer to instructions. The regiochemistry of hydroboration/oxidation of alkenes is:

A) Markovnikov.
B) non-Markovnikov
C) subject to solvent effects.
D) unrelated to alkene structure.

Question 19

Consider the reaction below to answer the following question(s).
Alkenes may be hydrated by the hydroboration/oxidation procedure shown.
Refer to instructions. The intermediate formed in the first step of this reaction is:

A)

B)

C)

D)

Question 20

Predict the major product of the following reaction.

Question 21

What type of reaction mechanism is involved in the reaction of an alcohol with aqueous acid to give an alkene?

A) nucleophilic addition
B) electrophilic addition
C) radical addition
D) elimination

Question 22

What type of reactive intermediate is formed in the reaction of an alkene with HBr to give a bromoalkane?

A) carbocation
B) carbanion
C) radical
D) cyclic bromonium ion

Question 23

Draw the structure of the polymer formed from the monomer given below, showing four repeating units.

Question 24

What type of reactive intermediate is formed in the reaction of an alkene with aqueous acid to give an alcohol?

A) carbocation
B) carbanion
C) radical
D) carbene

Question 25

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

Question 26

Circle whichever of the following would be classified as a conjugated diene.

Question 27

Draw the structure of the monomer used to prepare the polymer shown below.

Question 28

Draw all the isomeric products formed from the addition of HCl to the following compound.

Question 29

What is the best choice of reagents to perform the following transformation?

A) H₂O, H₂SO₄
B) Hg(OAc)₂ and H₂O; followed by NaBH₄
C) BH₃; followed by H₂O₂, NaOH
D) OsO₄; followed by NaHSO₃

Question 30

What type of reactive intermediate is involved in both of the following general reaction types? 1)
Reaction of an alkene with Br₂ in the presence of water to give a bromohydrin
2)
Two-step hydroxylation of an alkene

A) carbocation
B) carbanion
C) radical
D) cyclic bromonium ion
E) cyclic ion

Question 31

Complete the following reaction

Question 32

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

Question 33

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

Question 34

What type of reaction mechanism accounts for the reaction of an alkyne with HBr to give an alkyl bromide?

A) nucleophilic addition
B) electrophilic addition
C) radical addition
D) elimination

Question 35

On the structures provided, draw arrows showing the electron flow in the reaction mechanism for the electrophilic addition of hydrogen bromide to hex-1-yne.

Question 36

What type of reaction mechanism accounts for the reaction of an alkene with HBr to give an alkyl bromide?

A) nucleophilic addition
B) electrophilic addition
C) radical addition
D) elimination

Question 37

What is the best choice of reagents to perform the following transformation?

A) H₂O, H₂SO₄
B) HgSO₄; followed by NaBH₄
C) BH₃; followed by H₂O₂
D) OsO₄; followed by NaHSO₃

Question 38

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