Chapter 9 Practice Test

When preparing terminal alkynes by an elimination reaction, sodium amide (NaNH₂) dissolved in liquid ammonia (NH₃) is used most frequently. Which of the following statements offers the best explanation for the above statement?

• Sodium amide deprotonates the terminal alkyne, driving formation of the alkynide ion

• Only sodium amide is a strong enough base to deprotonate a carbon.

• The above statement is false; terminal alkynes are not produced under the given conditions.

• Terminal alkynes are more stable than the internal alkynes, and are always the favored product.

• Steric hindrance favors preparation of the less substituted terminal alkyne.

Consider the list of alkyne addition reactions below, and select all those that involve an enol intermediate.

• Hydroboration/oxidation

• HgSO₄ catalyzed hydration in dilute H₂SO₄

• Hydrohalogenation

• Both Hydroboration/oxidation and HgSO₄ catalyzed hydration in dilute H₂SO₄

• Both Hydroboration/oxidation and Hydrohalogenation

Which of the following is the acceptable structure for (R)-5-bromohept-2-yne?

• V

• I

• III

• IV

• II

Which of the following is the structure for 2-hexyne?

• III

• IV

• II

• I

Identify the expected major product from the treatment of 1-pentyne with 2 equivalents of HBr.

• 1,1-dibromopentane

• 2-bromo-1-pentene

• 2,2-dibromopentane

• 1,2-dibromopentane

• 1-bromo-1-pentene

Identify the final product for the following reaction.

• I

• V

• III

• II

• IV

For the reaction shown, select the expected major organic product.

• V

• I

• II

• IV

• III

Provide the IUPAC name for Cl₃CCH₂CH₂CH₂C≡CH.

• 5,5,5-trichloro-1-pentyne

• 1-heptyne

• 1,1,1-trichloro-5-hexyne

• 6,6,6-trichloro-1-hexyne

• trichlorobutylacetylene

Why would the following reaction sequence not produce the expected product shown?

• NaNH₂ is used in the reduction of alkynes to trans alkenes.

• Br is not a good enough leaving group.

• The terminal alkyne is not acidic enough to be deprotonated.

• The reaction sequence is correct and will produce the shown product.

• The secondary alkyl halide would undergo an elimination reaction.

What is the major expected product(s) of the reaction shown below?

• 2,2-dichloropentane

• 3,3-dichloropentane

• 2,3-dichloropentane

• 2,2-dichloropentane and 3,3-dichloropentane

• 3,3-dichloropentane and 2,3-dichloropentane

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2