Question 1

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

Accepted Answer

The sp hybridized carbon in alkynes is more electronegative than sp2 and sp3 carbons, stabilizing the negative charge.

Question 2

Which reagent is most suitable for deprotonating a terminal alkyne to generate an acetylide ion?

Accepted Answer

NaNH$_2$

Question 3

What is the major product when 2-butyne is treated with excess H$_2$ in the presence of Pt catalyst?

Accepted Answer

butane

Question 4

Which of the following best describes the result of ozonolysis of an internal alkyne?

Accepted Answer

Formation of two carboxylic acids

Question 5

When 1-hexyne undergoes hydration with HgSO$_4$ and H$_2$SO$_4$, what is the major organic product?

Accepted Answer

2-hexanone

Question 6

Which of the following is the correct IUPAC name for the compound shown below?

$\mathrm{CH_3CH_2C \equiv CCH_3}$

Accepted Answer

2-pentyne

Question 7

A student attempts to synthesize a terminal alkyne by treating 1,2-dibromopropane with excess NaNH$_2$. What is the expected product?

Accepted Answer

Propyne

Question 8

Which of the following reactions will produce a trans-alkene from an alkyne?

Accepted Answer

Reduction with Na in liquid NH$_3$

Question 9

Which statement correctly describes the Markovnikov addition of HBr to an alkyne?

Accepted Answer

The Br atom adds to the more substituted carbon of the triple bond.

Question 10

Which of the following best explains why three equivalents of NaNH$_2$ are used in the preparation of a terminal alkyne from a geminal dihalide?

Accepted Answer

To remove both halides and deprotonate the terminal alkyne

Question 11

Which of the following is a natural alkyne found in poison dart frogs?

Accepted Answer

Histrionicotoxin

Question 12

What is the product of anti-Markovnikov addition of HBr to 1-hexyne in the presence of ROOR?

Accepted Answer

1-bromo-1-hexene

Question 13

Which of the following best describes the hybridization of the carbon atoms in acetylene?

Accepted Answer

Both carbons are sp hybridized

Question 14

Which of the following is the correct order of acidity for the following compounds?

$\mathrm{CH_3CH_3}$, $\mathrm{H_2C=CH_2}$, $\mathrm{HC \equiv CH}$

Accepted Answer

$\mathrm{HC \equiv CH} > H_2C=CH_2 > CH_3CH_3$

Question 15

Which of the following is a correct description of keto-enol tautomerization in alkyne hydration reactions?

Accepted Answer

The keto form is more stable than the enol form.

Question 16

Which of the following is the correct product when 1-octyne is hydrated using HgSO$_4$ and H$_2$SO$_4$?

Accepted Answer

2-octanone

Question 17

Which of the following statements about the addition of halogens (X$_2$) to alkynes is correct?

Accepted Answer

The reaction proceeds through a bromonium or chloronium ion intermediate.

Question 18

Which of the following is the correct IUPAC name for a cyclohexane ring with an ethynyl group attached?

Accepted Answer

Ethynylcyclohexane

Question 19

Which of the following best describes the product of hydration of acetylene?

Accepted Answer

Acetaldehyde

Chapter 9: Alkynes – Structure, Properties, and Reactions

Study Guide - Practice Questions