Question 1

Which reagent is commonly used to convert an alkyne into a trans-alkene via partial hydrogenation?

Accepted Answer

Na/NH$$_3$$

Question 2

What is the major product when 1-butyne is treated with excess HBr?

Accepted Answer

2,2-dibromobutane

Question 3

Which sequence of reagents would you use to convert an alkene to an alkyne?

Accepted Answer

Br$$_2$$, then NaNH$$_2$$

Question 4

In retrosynthetic analysis, which of the following is a valid disconnection for synthesizing a terminal alkyne from an alkene?

Accepted Answer

Alkene $$ightarrow$$ dibromoalkane $$ightarrow$$ alkyne

Question 5

Which of the following best describes the role of NaNH$$_2 in $$organic synthesis?

Accepted Answer

It is used to deprotonate terminal alkynes, generating acetylide ions.

Question 6

A student wants to synthesize 2-pentyne from 1-pentene. Which of the following sequences is correct?

Accepted Answer

Br$$_2$$ addition, then NaNH$$_2$$ elimination

Question 7

Which product is formed when a terminal alkyne reacts with NaNH$$_2$$ followed by an alkyl halide?

Accepted Answer

An internal alkyne with a new carbon-carbon bond

Question 8

In the synthesis of an alkyne from an alkene, why is excess NaNH$$_2$$ used after dibromination?

Accepted Answer

To ensure complete elimination of both bromine atoms, forming the triple bond

Question 9

Which of the following is a correct retrosynthetic step for making an alkyne from an alkene?

Accepted Answer

Alkene $$ightarrow$$ vicinal dibromide $$ightarrow$$ alkyne

Question 10

A chemist wants to synthesize a trans-alkene from an alkyne. Which reagent should be used?

Accepted Answer

Na/NH$$_3$$

Question 11

Which of the following is the correct order of steps to convert an alkene to a terminal alkyne?

Accepted Answer

Br$$_2$$ addition, NaNH$$_2$$ elimination, deprotonation, alkylation

Question 12

What is the product when 2-butyne is treated with Lindlar's catalyst and H$$_2$$?

Accepted Answer

cis-2-butene

Question 13

Which of the following reactions is an example of an SN$$_2$$ mechanism in the synthesis of alkynes?

Accepted Answer

Alkylation of acetylide ion with a primary alkyl halide

Question 14

In a synthetic problem, which reagent would you use to selectively reduce an alkyne to a cis-alkene?

Accepted Answer

Lindlar's catalyst

Question 15

Which of the following is a correct application of retrosynthetic analysis for making a substituted alkyne?

Accepted Answer

Disconnection at the C-C triple bond, followed by alkylation of acetylide ion

Question 16

A student uses NaNH$$_2$$ and a primary alkyl halide to extend the carbon chain of a terminal alkyne. What is the mechanism?

Accepted Answer

SN$$_2$$ nucleophilic substitution

Question 17

Which of the following is NOT a correct use of NaNH$$_2 in $$organic synthesis?

Accepted Answer

Catalytic hydrogenation of alkynes to alkenes

Question 18

What is the expected product when a terminal alkyne is treated with NaNH$$_2$$ followed by ethyl bromide?

Accepted Answer

An internal alkyne with an ethyl group added

Question 19

Which of the following steps is necessary to convert a dibromoalkane to an alkyne?

Accepted Answer

Treatment with excess NaNH$$_2$$

Question 20

In a multi-step synthesis, which reagent is used to add two bromine atoms across an alkene?

Accepted Answer

Br$$_2$$

Alkynes as Nucleophiles and Synthetic Applications in Organic Chemistry

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