Question 1

Which of the following statements correctly describes the difference between a terminal and an internal alkyne?

Accepted Answer

A terminal alkyne has the triple bond at the end of the carbon chain, with one carbon of the triple bond bonded to a hydrogen.

Question 2

What is the correct IUPAC name for the following compound: $$CH_3CH_2C\equiv CCH_2CH_3$$?

Accepted Answer

2-hexyne

Question 3

When excess $$HBr is $$added to 2-butyne, what is the major product?

Accepted Answer

$$CH_3CHBrCHBrCH_3$$

Question 4

Which reagent and conditions would you use to convert a terminal alkyne into an aldehyde?

Accepted Answer

Hydroboration-oxidation: $$1. BH_3$, 2. H_2O_2/NaOH$$

Question 5

Which of the following best explains why the hydrogen attached to an sp-hybridized carbon in ethyne is more acidic than the hydrogen in ethene or ethane?

Accepted Answer

The sp-hybridized carbon is more electronegative, stabilizing the negative charge on the conjugate base.

Question 6

A student wants to synthesize 3-heptyne from a terminal alkyne. Which sequence of reactions would achieve this?

Accepted Answer

Deprotonation of 1-pentyne with $$NaNH_2$$, followed by reaction with 1-bromopropane.

Question 7

Which of the following is the product of acid-catalyzed hydration of 2-pentyne?

Accepted Answer

3-pentanone

Question 8

What is the major product when 1-hexyne is treated with excess $$Br_2 in$$ $$CCl_4$$?

Accepted Answer

1,1,2,2-tetrabromohexane

Question 9

Which catalyst is used to selectively hydrogenate an alkyne to a cis-alkene?

Accepted Answer

Lindlar's catalyst

Question 10

Which of the following statements about the addition of $$HCl to a $$terminal alkyne is correct?

Accepted Answer

The hydrogen adds to the less substituted carbon, and the chlorine adds to the more substituted carbon.

Question 11

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

Accepted Answer

Amide ion ($$NH_2$$^-$$)

Question 12

What is the product of hydroboration-oxidation of 2-butyne?

Accepted Answer

Butanone

Question 13

Which of the following is true regarding the regioselectivity of electrophilic addition to an asymmetrical internal alkyne?

Accepted Answer

Two different products are formed because the electrophile can add to either carbon of the triple bond.

Question 14

Which of the following best describes the product of the reaction of 1-butyne with $$H_2O$$, $$H_2SO_4$$, and $$HgSO_4$$?

Accepted Answer

Butanone via keto-enol tautomerization

Question 15

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

Accepted Answer

Alkynes are soluble in nonpolar solvents and are less dense than water.

Question 16

Which of the following reactions will convert an alkyne to a trans-alkene?

Accepted Answer

Reduction with sodium in liquid ammonia ($$Na/NH_3)$$

Question 17

When naming a compound with both a double and a triple bond, which bond gets the lower number if a tie occurs?

Accepted Answer

The double bond

Question 18

Which of the following is the correct product when 1-butyne is treated with $$NaNH_2$$ followed by $$CH_3Br$$?

Accepted Answer

2-pentyne

Question 19

Which of the following is a real-world application of alkynes?

Accepted Answer

Pargyline is an antihypertensive drug containing an alkyne functional group.

Chapter 7: The Reactions of Alkynes and Multistep Synthesis – Study Notes

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