Question 1

Which of the following statements best describes the difference in acidity between ethyne ($$HC\equiv CH$$), ethene ($$H_2C=CH_2$), and ethane (CH_3CH_3$)?

Accepted Answer

Ethyne is more acidic than both ethene and ethane because the sp-hybridized carbon holds negative charge more effectively.

Question 2

When naming an alkyne with both a triple bond and a double bond, which functional group receives the lowest possible number if a tie occurs?

Accepted Answer

The double bond receives the lowest number in case of a tie.

Question 3

Which reagent is required to convert a terminal alkyne into an acetylide ion for subsequent alkylation?

Accepted Answer

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

Question 4

What is the product when 1-butyne ($$CH_3C\equiv CCH_2CH_3) $$undergoes hydroboration-oxidation ($$1.\ 9-$$BBN/THF, $$2.\ H_2O_2$$, $$OH^-$$)?

Accepted Answer

Butanal

Question 5

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

Accepted Answer

Lindlar catalyst

Question 6

A student attempts to alkylate a terminal alkyne using $$CH_3CH_2Br$$ and $$OH^-. $$What is the expected outcome?

Accepted Answer

No reaction, because $$OH^- is $$not a strong enough base to generate the acetylide ion.

Question 7

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

Accepted Answer

The sp-hybridized carbon in alkynes is more electronegative, stabilizing the negative charge.

Question 8

What is the major product when 2-pentyne reacts with excess $$HBr$$?

Accepted Answer

2,2-dibromopentane

Question 9

Which of the following is a naturally occurring alkyne with convulsant properties?

Accepted Answer

Ichthyothereol

Question 10

During the hydration of a terminal alkyne using $$HgSO_4$$ and $$H_2SO_4$$, what is the initial product before tautomerization?

Accepted Answer

Enol

Question 11

Which of the following best describes the geometry around the carbon atoms in an alkyne?

Accepted Answer

Linear, with bond angles of $$180^\circ$$

Question 12

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

Accepted Answer

2-hexyne

Question 13

What is the expected product when trans-2-butene is treated with $$Br_2 in$$ $$CCl_4$$?

Accepted Answer

2,3-dibromobutane (anti addition)

Question 14

Which synthetic alkyne is used as an antihypertensive drug?

Accepted Answer

Pargyline

Question 15

What is the product when a terminal alkyne reacts with $$Br_2 in $$excess?

Accepted Answer

A tetrahalide (geminal and vicinal dibromides)

Question 16

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

Accepted Answer

The reaction produces a mixture of products due to lack of regioselectivity.

Question 17

Which of the following is the correct formula for a cyclic alkyne with 6 carbon atoms?

Accepted Answer

$$C_6H_8$$

Question 18

What is the major product when 1-hexyne is treated with $$Na/NH_3 ($$Birch reduction conditions)?

Accepted Answer

trans-2-hexene

Question 19

Which of the following best describes the intermediate formed during electrophilic addition to an alkyne?

Accepted Answer

A pi-complex

Question 20

Which of the following is the correct IUPAC name for $$CH_3CH_2C\equiv CCH_2OH$$?

Accepted Answer

4-hexyn-1-ol

Chapter 7: The Reactions of Alkynes and Introduction to Multistep Synthesis

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