Question 1

Which reagent(s) would you use to convert a vicinal dihalide to an alkyne in a laboratory synthesis?

Accepted Answer

Excess $$\mathrm{NaNH}_2$$ followed by $$\mathrm{H}_2\mathrm{O}$$

Question 2

What is the major organic product when 1-butyne reacts with excess $$\mathrm{HBr}$$?

Accepted Answer

2,2-dibromobutane

Question 3

Which of the following best describes the product(s) formed when 2-hexyne is treated with 1 equivalent of $$\mathrm{Br}_2$$?

Accepted Answer

A trans-dibromoalkene

Question 4

A terminal alkyne is treated with $$\mathrm{H}_2\mathrm{O}, \mathrm{H}_2\mathrm{SO}_4$$, and $$\mathrm{HgSO}_4. $$What is the final major product after tautomerization?

Accepted Answer

A ketone

Question 5

Which reagent is specifically used for hydroboration-oxidation of terminal alkynes to yield aldehydes?

Accepted Answer

Disiamylborane

Question 6

What is the product when an internal alkyne is treated with $$\mathrm{Na} in $$liquid $$\mathrm{NH}_3$$?

Accepted Answer

A trans-alkene

Question 7

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

Accepted Answer

The sp hybridized carbon holds electrons closer, stabilizing the negative charge

Question 8

A student wants to synthesize 2-hexyne from 1,2-dibromohexane. Which sequence of reagents should be used?

Accepted Answer

1. Excess $$\mathrm{NaNH}_2$$; 2. $$\mathrm{H}_2\mathrm{O}$$

Question 9

What is the expected product when 1-hexyne undergoes ozonolysis followed by hydrolysis?

Accepted Answer

Hexanoic acid and carbon dioxide

Question 10

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

Accepted Answer

Lindlar catalyst

Question 11

A terminal alkyne is treated with $$\mathrm{NaNH}_2$$ followed by $$\mathrm{CH}_3CH_2CH_2Br. $$What is the major product?

Accepted Answer

A new terminal alkyne with a propyl group attached

Question 12

Which of the following is true about the addition of $$\mathrm{HBr} to an $$unsymmetrical internal alkyne?

Accepted Answer

Both possible regioisomers are formed

Question 13

What is the product of hydroboration-oxidation of 1-butyne?

Accepted Answer

Butanal

Question 14

Which of the following best describes the product when 2-butyne is treated with $$\mathrm{H}_2, \mathrm{Pd}/\mathrm{C}$$?

Accepted Answer

Butane

Question 15

A student treats 2-hexyne with $$\mathrm{H}_2, \mathrm{Lindlar}$$ catalyst. What is the expected product?

Accepted Answer

cis-2-hexene

Question 16

Which of the following is a correct statement about the reaction of alkynes with $$\mathrm{Br}_2$$?

Accepted Answer

One equivalent yields a dibromoalkene, excess yields a tetrabromoalkane

Question 17

What is the major product when 1-hexyne is treated with $$\mathrm{H}_2\mathrm{O}, \mathrm{H}_2\mathrm{SO}_4$$, and $$\mathrm{HgSO}_4$$?

Accepted Answer

2-hexanone

Question 18

Which of the following is the correct product of the reaction: $$\mathrm{CH}_3C\equiv $$CCH_3$$ + excess $$\mathrm{Br}_2$$?

Accepted Answer

1,1,2,2-tetrabromo-2-butane

Question 19

Which of the following statements is true regarding the use of Lindlar catalyst in alkyne hydrogenation?

Accepted Answer

It selectively produces cis-alkenes from internal alkynes

Reactions of Alkynes: Ch 9

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