Deck 7: The Reactions of Alkynes an Introduction Tomultistep Synthesis

Question 1

What is the systematic name for the following compound? ?

A) 3-ethynyl-1-hexene
B) 3-ethenyl-1-hexyne
C) 3-propyl-4-penten-1-yne
D) 3-propyl-1-penten-4-yne
E) 3-propyl-1,4-pentenyne

Answer 1

3-propyl-1-penten-4-yne

Question 2

What is the systematic name for the following compound?

A) 1,1-diethynylethane
B) 3-ethynylbutyne
C) 3-butynylethyne
D) 3-ethynyl-1-butyne
E) 3-methyl-1,4-pentadiyne

Answer 2

3-methyl-1,4-pentadiyne

Question 3

Why are alkynes less reactive toward electrophilic addition?

A) Triple bonds are stronger than double bonds.
B) Only one ? bond must be broken in the addition of an electrophile to an alkene.
C) The ?-complex that is formed from an alkyne is less stable than the alkyl cation intermediate that is formed from an alkene.
D) Alkynes are less stable than alkenes.
E) Hyperconjugation stabilizes the intermediate from an alkyne more than the intermediate from an alkene.

Answer 3

The ?-complex that is formed from an alkyne is less stable than the alkyl cation intermediate that is formed from an alkene.

Question 4

Which product is expected from the reaction shown here?

A)
B)
C)
D)
E)

Question 5

Which product would be isolated from the reaction shown?

A)
B)
C)
D)
E)

Question 6

Which reagent is the best choice to complete the following transformation?

A) Na, NH_3(liq)
B) NaNH₂
C) 1. NaBH₄, 2. H₃O⁺
D) 1 mole H₂/Pd/C
E) H₂, Lindlar catalyst

Question 7

Which of the following statements is not true?

A) Alkynes undergo electrophilic addition reactions.
B) Alkynes are less reactive than alkenes in electrophilic addition reactions.
C) Sodium in liquid ammonia is used to form cis alkenes.
D) Catalytic hydrogenation of an alkyne in the presence of Pd/C gives complete reduction.
E) Reaction of an alkyne with water under acidic conditions gives an enol.

Question 8

Which base is strong enough to deprotonate 1-octyne completely?

A) NaF
B) NaOH
C) NH₃
D) NaOCH₃
E) NaNH₂

Question 9

Which of the following methods would give the product in reasonable yield?

A) 1. NaNH₂ 2. CH₂=CHCH₂Br 3. H₂O, H₂SO₄
B) 1. NaNH₂ 2. CH₂=CHCH₂Br 3. HCl
C) 1. NaNH₂ 2. CH₂=CHCH₂Br 3. R₂BH/THF 4. HO^?,H₂O₂, H₂O
D) 1. NaNH₂ 2. HOCH₂CHCH₂Br 3. R₂BH/THF 4. HO^?, H₂O₂, H₂O
E) all of the above

Question 10

Which of the following sets of reactions accomplish the synthesis shown below?

A) 1. NaNH₂ 2. CH₃CH₂CH₂Br 3. Na/NH_3(liq) 4. HBr
B) 1. NaOH 2. CH₃CH₂Br 3. H₂, Lindlar cat 4. Br₂/H₂O
C) 1. NaNH₂ 2. CH₃CH₂I 3. H₂, Lindlar cat 4. Br₂
D) 1. H₂, Lindlar cat 2. NaNH₂ 3. CH₃CH₂Br 4. Br₂
E) 1. Na/NH_3(liq) 2. NaNH₂ 3. CH₃CH₂I 4. HBr

Question 11

Which of the following sets of reactions accomplishes the synthesis shown below?

A) 1. NaNH₂ 2. CH₂=CHCH₂Br 3. H₂, Lindlar 4. BH₃/THF 5. HO^?,H₂O₂, H₂O
B) 1. NaNH₂ 2. CH₂=CHCH₂Br 3. MCPBA
C) 1. NaNH₂ 2. CH₃CH₂CH₂Br 3. BH₃/THF 4. HO^?,H₂O₂, H₂O
D) 1. NaNH₂ 2. CH₂=CHCH₂Br 3. Na/NH_3(liq) 4. MCPBA
E) 1. NaNH₂ 2. CH₃CH₂CH₂Br 4. 9-BBN-THF 5. HO^-,H₂O₂, H₂O

Question 12

Rank the following carbocations in order of decreasing stability.

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