Question 1

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

Accepted Answer

The sp-hybridized carbon in terminal alkynes holds the negative charge closer to the nucleus, stabilizing the conjugate base.

Question 2

What is the product of the complete catalytic hydrogenation of 2-butyne using excess $$\mathrm{H_2$}$$ and a platinum catalyst?

Accepted Answer

Butane

Question 3

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

Accepted Answer

Lindlar’s catalyst

Question 4

A terminal alkyne is treated with $$\mathrm{$$NaNH_2$$}$$ followed by $$\mathrm{CH_3Br}. $$What is the major product?

Accepted Answer

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

Question 5

Which of the following best describes the product(s) of ozonolysis of a terminal alkyne?

Accepted Answer

A carboxylic acid and carbon dioxide

Question 6

What is the expected product when 1-hexyne undergoes hydroboration-oxidation ($$\mathrm{1.} \ \mathrm{R_2BH} \ \mathrm{2.} \ \mathrm{H_2O_2, OH^-}$$)?

Accepted Answer

Hexanal

Question 7

Which of the following is true regarding the mechanism of dissolving metal reduction (Birch reduction) of alkynes?

Accepted Answer

It produces a trans-alkene via anti addition of hydrogen atoms.

Question 8

Which of the following bases is strong enough to deprotonate a terminal alkyne?

Accepted Answer

$$\mathrm{$$NaNH_2$$}$$

Question 9

What is the major product when 2-butyne is treated with one equivalent of $$\mathrm{Br_2$} in$$ $$\mathrm{$$CCl_4$$}$$?

Accepted Answer

A mixture of cis- and trans-2,3-dibromobutene

Question 10

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

Accepted Answer

Addition of excess HX to an alkyne yields a geminal dihalide.

Question 11

Which of the following best describes the regiochemistry of hydration of a terminal alkyne using $$\mathrm{$$HgSO_4$$}$$ and $$\mathrm{H_2SO_4}$$?

Accepted Answer

Markovnikov addition, yielding a ketone after tautomerization

Question 12

Which of the following is a correct statement about the alkylation of terminal alkynes?

Accepted Answer

Alkylation works best with methyl or primary alkyl halides via an $$\mathrm{S_N2}$$ mechanism.

Question 13

Which of the following sequences would convert 1-butyne to 2-butanone?

Accepted Answer

1. $$\mathrm{$$HgSO_4$$, H_2SO_4} 2$$. $$\mathrm{H_2O}$$

Question 14

Which of the following is a correct statement about the halogenation of alkynes?

Accepted Answer

Addition of two equivalents of $$\mathrm{Br_2$} to an $$alkyne yields a tetrahalide.

Question 15

Which of the following best describes the product of ozonolysis of the following compound: $$\mathrm{C_5H_8} (a $$symmetrical internal alkyne)?

Accepted Answer

Two equivalents of a carboxylic acid

Question 16

Which of the following is the correct IUPAC name for the compound with the structure $$\mathrm{CH_3C \equiv CCH_2CH_3}$$?

Accepted Answer

2-Pentyne

Question 17

Which of the following statements about the mechanism of hydrohalogenation of alkynes is correct?

Accepted Answer

The rate law is first order in alkyne and second order in HX: $$\mathrm{rate = k[alkyne][HX]^2}$$

Question 18

Which of the following is a correct statement about the use of borane reagents in hydroboration-oxidation of alkynes?

Accepted Answer

Dialkyl boranes are used to prevent double addition to the alkyne.

Step-by-Step Guidance for Alkynes (Organic Chemistry, Chapter 9)

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