Question 1

Which of the following statements best explains why terminal alkynes are more acidic than alkenes and alkanes?

Accepted Answer

Terminal alkynes have sp hybridized carbons, which hold the negative charge closer to the nucleus, stabilizing the conjugate base.

Question 2

What is the correct IUPAC name for the following compound: $CH_3C \equiv CCH_2CH_3$?

Accepted Answer

2-pentyne

Question 3

Which reagent would you use to selectively reduce an alkyne to a cis-alkene?

Accepted Answer

$H_2$, Lindlar's catalyst

Question 4

A student wants to prepare an alkyne from a vicinal dihalide. Which of the following best describes the process?

Accepted Answer

Double elimination using a strong base such as $NaNH_2$

Question 5

Which of the following is the major product when 1 mol of $HBr$ is added to 1-hexyne?

Accepted Answer

2-bromohexane

Question 6

What is the expected product when a terminal alkyne reacts with $NaNH_2$ followed by $CH_3Br$?

Accepted Answer

An internal alkyne with a methyl group added to the terminal carbon

Question 7

Which of the following statements about the hydration of alkynes is correct?

Accepted Answer

Hydration of alkynes with $HgSO_4$ and $H_2SO_4$ produces ketones via Markovnikov addition.

Question 8

Which of the following best describes the difference between geminal and vicinal dihalides?

Accepted Answer

Geminal dihalides have both halides on the same carbon, while vicinal dihalides have halides on adjacent carbons.

Question 9

Which of the following reagents would you use to convert an alkyne to a trans-alkene?

Accepted Answer

$Na$, $NH_3$(l)

Question 10

A terminal alkyne is treated with $NaNH_2$ and then $CH_3CH_2Br$. What is the major product?

Accepted Answer

An internal alkyne with an ethyl group added to the terminal carbon

Question 11

Which of the following best explains why $NaNH_2$ is used in the alkylation of terminal alkynes?

Accepted Answer

$NaNH_2$ is a strong base that deprotonates the terminal alkyne, generating a nucleophilic acetylide ion.

Question 12

What is the product of ozonolysis of 2-butyne ($CH_3C \equiv CCH_3$) under oxidative conditions?

Accepted Answer

Two molecules of acetic acid ($CH_3COOH$)

Question 13

Which of the following is true about the addition of $Br_2$ to an alkyne?

Accepted Answer

Both anti and syn addition are observed when one equivalent is added.

Question 14

Which of the following best describes the Markovnikov addition of $HBr$ to an alkyne?

Accepted Answer

The hydrogen adds to the carbon with more hydrogens, and the bromine adds to the more substituted carbon.

Question 15

Which of the following is the correct order of acidity (from strongest to weakest acid) for the following compounds: ethyne, ethene, ethane?

Accepted Answer

$ethyne > ethene > ethane$

Question 16

Which of the following reagents would you use to convert a terminal alkyne to a methyl ketone?

Accepted Answer

$HgSO_4$, $H_2SO_4$

Question 17

A student treats a terminal alkyne with $BH_3$ followed by $H_2O_2$ and $NaOH$. What is the major product?

Accepted Answer

An aldehyde formed via anti-Markovnikov hydration

Question 18

Which of the following best describes the product of the complete reduction of an alkyne with $H_2$ and Pd/C?

Accepted Answer

An alkane

Question 19

Which of the following is a correct statement about tautomerization in alkyne hydration reactions?

Accepted Answer

Tautomerization converts an enol intermediate to a ketone or aldehyde.

Alkynes: Structure, Properties, and Reactions

Study Guide - Practice Questions