Question 1

Which of the following statements about the structure and bonding in alkynes is correct?

Accepted Answer

Alkynes have a linear geometry with bond angles of $$180^\circ$$ due to sp hybridization.

Question 2

What is the correct IUPAC name for a molecule with a ten-carbon chain, a triple bond at carbon 2, a double bond at carbon 5, and a methyl group at carbon 5 (with the double bond in the E configuration)?

Accepted Answer

(E)-5-methyldec-5-en-2-yne

Question 3

Which reagent(s) would you use to selectively hydrogenate an alkyne to a cis-alkene?

Accepted Answer

Lindlar catalyst

Question 4

What is the general formula for an alkyne?

Accepted Answer

$$\mathrm{C_nH_{2n}}$$

Question 5

Which of the following correctly describes the acidity trend among alkanes, alkenes, and alkynes?

Accepted Answer

Alkynes are more acidic than alkenes and alkanes.

Question 6

Which base is strong enough to deprotonate a terminal alkyne?

Accepted Answer

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

Question 7

What is the major product when a terminal alkyne reacts with excess $$\mathrm{HBr}$$?

Accepted Answer

A geminal dibromide

Question 8

Which of the following is a key step in the preparation of alkynes by alkylation of acetylene?

Accepted Answer

Formation of a carbon-carbon bond via $$\mathrm{S_N2}$$ reaction

Question 9

Which of the following statements about the physical properties of alkynes is correct?

Accepted Answer

Alkynes have low density and low water solubility, similar to alkanes and alkenes.

Question 10

What is the product of the hydration of a terminal alkyne in the presence of $$\mathrm{H_2SO_4}$$, $$\mathrm{$$HgSO_4$$}$$, and water?

Accepted Answer

A ketone formed via enol-keto tautomerization

Question 11

Which of the following best describes the outcome when an internal alkyne is treated with $$\mathrm{Na} in$$ $$\mathrm{NH_3$}$$?

Accepted Answer

A trans-alkene is formed.

Question 12

Which of the following is NOT a correct statement about the preparation of alkynes by elimination reactions?

Accepted Answer

Double dehydrohalogenation of a vicinal dihalide yields a terminal alkyne.

Question 13

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

Accepted Answer

$$\mathrm{Na/NH_3$}$$

Question 14

What is the major product when an internal alkyne is treated with excess $$\mathrm{HBr}$$?

Accepted Answer

A mixture of two geminal dibromides (one at each end)

Question 15

Which of the following is the correct order of acidity (most to least acidic) for the following: alkane, alkene, alkyne?

Accepted Answer

Alkyne \u003e alkene \u003e alkane

Question 16

Which of the following is a limitation of preparing alkynes by elimination reactions?

Accepted Answer

The reaction cannot produce terminal alkynes from geminal dihalides.

Question 17

Which of the following best describes the product of catalytic hydrogenation of an alkyne with $$\mathrm{Pd/C}$$?

Accepted Answer

An alkane

Question 18

Which of the following is true about the reaction of a terminal alkyne with $$\mathrm{$$NaNH_2$$}$$ followed by an alkyl halide?

Accepted Answer

It forms a new carbon-carbon bond via an $$\mathrm{S_N2}$$ mechanism.

Alkynes: Structure, Properties, Nomenclature, and Reactions

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