Question 1

Which of the following statements correctly describes the hybridization and geometry of the carbon atoms in ethyne (acetylene)?

Accepted Answer

The carbon atoms are sp hybridized, giving the molecule a linear shape.

Question 2

What is the general molecular formula for an alkyne?

Accepted Answer

$$C_nH_{2n-2}$$

Question 3

Which of the following reagents would you use to convert a terminal alkyne into a sodium acetylide ion?

Accepted Answer

Sodium amide ($$NaNH_2)$$

Question 4

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

Accepted Answer

The sp hybridized carbon in alkynes has more s character, so the negative charge on the conjugate base is held closer to the nucleus and is more stable.

Question 5

A student wants to synthesize 3-heptyne from a terminal alkyne. Which sequence of reagents should they use?

Accepted Answer

1) $$NaNH_2 2$$) $$CH_3CH_2CH_2Br$$

Question 6

Which product is formed when 2-butyne is treated with excess $$H_2 in $$the presence of a palladium catalyst?

Accepted Answer

Butane

Question 7

What is the major product when 1-hexyne is treated with $$HBr in $$the presence of peroxides?

Accepted Answer

1-Bromohexene (anti-Markovnikov addition)

Question 8

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

Accepted Answer

Addition of $$Br_2 to an $$alkyne forms a mixture of cis and trans dibromoalkenes.

Question 9

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

Accepted Answer

Lindlar's catalyst

Question 10

A terminal alkyne undergoes hydroboration-oxidation. What is the final product after tautomerization?

Accepted Answer

An aldehyde

Question 11

Which of the following best describes the outcome when 2-pentyne is treated with warm, basic $$KMnO_4$$?

Accepted Answer

The triple bond is cleaved, producing two carboxylic acids.

Question 12

Which of the following is the correct IUPAC name for the compound $$CH_3CH_2C\equiv CCH_2CH_3$$?

Accepted Answer

3-Hexyne

Question 13

When a terminal alkyne reacts with $$HgSO_4$$ and $$H_2SO_4 in $$water, what is the major product after tautomerization?

Accepted Answer

A methyl ketone

Question 14

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

Accepted Answer

Alkynes are more dense than water.

Question 15

Which of the following best describes the bonding in an alkyne?

Accepted Answer

One sigma bond formed by sp-sp overlap and two pi bonds formed by unhybridized p orbitals at 90°.

Question 16

Which of the following is the correct order of functional group priority for IUPAC nomenclature (from highest to lowest) as it relates to alkynes?

Accepted Answer

Carboxylic acid \u003e ester \u003e amide \u003e nitrile \u003e aldehyde \u003e ketone \u003e alcohol \u003e amine \u003e alkene \u003e alkyne

Question 17

A chemist treats 1-butyne with $$NaNH_2$$ followed by $$CH_3CH_2Br. $$What is the major product?

Accepted Answer

1-Hexyne

Question 18

Which of the following best describes the product of ozonolysis of 3-hexyne followed by hydrolysis?

Accepted Answer

Two molecules of propanoic acid

Question 19

Which of the following is a correct statement about the reaction of alkynes with $$KMnO_4$$ under neutral, dilute conditions?

Accepted Answer

A diketone is formed.

Question 20

Which of the following best explains why acetylide ions are good nucleophiles in organic synthesis?

Accepted Answer

The negative charge is localized on a carbon with high s character, making it both basic and nucleophilic.

Alkynes: Structure, Nomenclature, Properties, and Reactions

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